Update license to GPL-3.0+

The README file was showing *very* out-of-date information. The README
now shows proper documentation, with everything being consistent.

.gitignore

@@ -12,5 +12,14 @@ Cargo.lock
 # These are backup files generated by rustfmt
 **/*.rs.bk
 
+### VisualStudioCode ###
+.vscode/
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+.history
 
 # End of https://www.gitignore.io/api/rust
+
+sterling-conf.yml

.gitlab-ci.yml

@@ -0,0 +1,12 @@
+image: "rust:latest"
+stages:
+  - test
+  - deploy
+
+cargo:test:
+  stage: test  
+  only:
+    - master
+  script:
+    - cargo test --verbose
+    - cargo bench

.travis.yml

@@ -0,0 +1,62 @@
+# Based on the "trust" template v0.1.2
+# https://github.com/japaric/trust/tree/v0.1.2
+
+dist: trusty
+language: rust
+services: docker
+sudo: required
+
+env:
+  global:
+    # TODO Update this to match the name of your project.
+    - CRATE_NAME=sterling
+
+matrix:
+  include:
+    # Linux
+    - env: TARGET=x86_64-unknown-linux-gnu
+
+    # OSX
+    - env: TARGET=x86_64-apple-darwin
+      os: osx
+
+before_install:
+  - set -e
+  - rustup self update
+
+install:
+  - sh ci/install.sh
+  - source ~/.cargo/env || true
+
+script:
+  - bash ci/script.sh
+
+after_script: set +e
+
+before_deploy:
+  - sh ci/before_deploy.sh
+
+deploy:
+  api_key:
+    secure: "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"
+  file_glob: true
+  file: $CRATE_NAME-$TRAVIS_TAG-$TARGET.*
+  on:
+    tags: true
+  provider: releases
+  skip_cleanup: true
+
+cache: cargo
+before_cache:
+  # Travis can't cache files that are not readable by "others"
+  - chmod -R a+r $HOME/.cargo
+
+branches:
+  only:
+    # release tags
+    - /^v\d+\.\d+\.\d+.*$/
+    # - master
+
+notifications:
+  email:
+    on_success: never

COPYING

@@ -0,0 +1,594 @@
+# GNU General Public License
+
+_Version 3, 29 June 2007_  
+_Copyright © 2007 Free Software Foundation, Inc. &lt;<http://fsf.org/>&gt;_
+
+Everyone is permitted to copy and distribute verbatim copies of this license
+document, but changing it is not allowed.
+
+## Preamble
+
+The GNU General Public License is a free, copyleft license for software and other
+kinds of works.
+
+The licenses for most software and other practical works are designed to take away
+your freedom to share and change the works. By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change all versions of a
+program--to make sure it remains free software for all its users. We, the Free
+Software Foundation, use the GNU General Public License for most of our software; it
+applies also to any other work released this way by its authors. You can apply it to
+your programs, too.
+
+When we speak of free software, we are referring to freedom, not price. Our General
+Public Licenses are designed to make sure that you have the freedom to distribute
+copies of free software (and charge for them if you wish), that you receive source
+code or can get it if you want it, that you can change the software or use pieces of
+it in new free programs, and that you know you can do these things.
+
+To protect your rights, we need to prevent others from denying you these rights or
+asking you to surrender the rights. Therefore, you have certain responsibilities if
+you distribute copies of the software, or if you modify it: responsibilities to
+respect the freedom of others.
+
+For example, if you distribute copies of such a program, whether gratis or for a fee,
+you must pass on to the recipients the same freedoms that you received. You must make
+sure that they, too, receive or can get the source code. And you must show them these
+terms so they know their rights.
+
+Developers that use the GNU GPL protect your rights with two steps: **(1)** assert
+copyright on the software, and **(2)** offer you this License giving you legal permission
+to copy, distribute and/or modify it.
+
+For the developers' and authors' protection, the GPL clearly explains that there is
+no warranty for this free software. For both users' and authors' sake, the GPL
+requires that modified versions be marked as changed, so that their problems will not
+be attributed erroneously to authors of previous versions.
+
+Some devices are designed to deny users access to install or run modified versions of
+the software inside them, although the manufacturer can do so. This is fundamentally
+incompatible with the aim of protecting users' freedom to change the software. The
+systematic pattern of such abuse occurs in the area of products for individuals to
+use, which is precisely where it is most unacceptable. Therefore, we have designed
+this version of the GPL to prohibit the practice for those products. If such problems
+arise substantially in other domains, we stand ready to extend this provision to
+those domains in future versions of the GPL, as needed to protect the freedom of
+users.
+
+Finally, every program is threatened constantly by software patents. States should
+not allow patents to restrict development and use of software on general-purpose
+computers, but in those that do, we wish to avoid the special danger that patents
+applied to a free program could make it effectively proprietary. To prevent this, the
+GPL assures that patents cannot be used to render the program non-free.
+
+The precise terms and conditions for copying, distribution and modification follow.
+
+## TERMS AND CONDITIONS
+
+### 0. Definitions
+
+“This License” refers to version 3 of the GNU General Public License.
+
+“Copyright” also means copyright-like laws that apply to other kinds of
+works, such as semiconductor masks.
+
+“The Program” refers to any copyrightable work licensed under this
+License. Each licensee is addressed as “you”. “Licensees” and
+“recipients” may be individuals or organizations.
+
+To “modify” a work means to copy from or adapt all or part of the work in
+a fashion requiring copyright permission, other than the making of an exact copy. The
+resulting work is called a “modified version” of the earlier work or a
+work “based on” the earlier work.
+
+A “covered work” means either the unmodified Program or a work based on
+the Program.
+
+To “propagate” a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for infringement under
+applicable copyright law, except executing it on a computer or modifying a private
+copy. Propagation includes copying, distribution (with or without modification),
+making available to the public, and in some countries other activities as well.
+
+To “convey” a work means any kind of propagation that enables other
+parties to make or receive copies. Mere interaction with a user through a computer
+network, with no transfer of a copy, is not conveying.
+
+An interactive user interface displays “Appropriate Legal Notices” to the
+extent that it includes a convenient and prominently visible feature that **(1)**
+displays an appropriate copyright notice, and **(2)** tells the user that there is no
+warranty for the work (except to the extent that warranties are provided), that
+licensees may convey the work under this License, and how to view a copy of this
+License. If the interface presents a list of user commands or options, such as a
+menu, a prominent item in the list meets this criterion.
+
+### 1. Source Code
+
+The “source code” for a work means the preferred form of the work for
+making modifications to it. “Object code” means any non-source form of a
+work.
+
+A “Standard Interface” means an interface that either is an official
+standard defined by a recognized standards body, or, in the case of interfaces
+specified for a particular programming language, one that is widely used among
+developers working in that language.
+
+The “System Libraries” of an executable work include anything, other than
+the work as a whole, that **(a)** is included in the normal form of packaging a Major
+Component, but which is not part of that Major Component, and **(b)** serves only to
+enable use of the work with that Major Component, or to implement a Standard
+Interface for which an implementation is available to the public in source code form.
+A “Major Component”, in this context, means a major essential component
+(kernel, window system, and so on) of the specific operating system (if any) on which
+the executable work runs, or a compiler used to produce the work, or an object code
+interpreter used to run it.
+
+The “Corresponding Source” for a work in object code form means all the
+source code needed to generate, install, and (for an executable work) run the object
+code and to modify the work, including scripts to control those activities. However,
+it does not include the work's System Libraries, or general-purpose tools or
+generally available free programs which are used unmodified in performing those
+activities but which are not part of the work. For example, Corresponding Source
+includes interface definition files associated with source files for the work, and
+the source code for shared libraries and dynamically linked subprograms that the work
+is specifically designed to require, such as by intimate data communication or
+control flow between those subprograms and other parts of the work.
+
+The Corresponding Source need not include anything that users can regenerate
+automatically from other parts of the Corresponding Source.
+
+The Corresponding Source for a work in source code form is that same work.
+
+### 2. Basic Permissions
+
+All rights granted under this License are granted for the term of copyright on the
+Program, and are irrevocable provided the stated conditions are met. This License
+explicitly affirms your unlimited permission to run the unmodified Program. The
+output from running a covered work is covered by this License only if the output,
+given its content, constitutes a covered work. This License acknowledges your rights
+of fair use or other equivalent, as provided by copyright law.
+
+You may make, run and propagate covered works that you do not convey, without
+conditions so long as your license otherwise remains in force. You may convey covered
+works to others for the sole purpose of having them make modifications exclusively
+for you, or provide you with facilities for running those works, provided that you
+comply with the terms of this License in conveying all material for which you do not
+control copyright. Those thus making or running the covered works for you must do so
+exclusively on your behalf, under your direction and control, on terms that prohibit
+them from making any copies of your copyrighted material outside their relationship
+with you.
+
+Conveying under any other circumstances is permitted solely under the conditions
+stated below. Sublicensing is not allowed; section 10 makes it unnecessary.
+
+### 3. Protecting Users' Legal Rights From Anti-Circumvention Law
+
+No covered work shall be deemed part of an effective technological measure under any
+applicable law fulfilling obligations under article 11 of the WIPO copyright treaty
+adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention
+of such measures.
+
+When you convey a covered work, you waive any legal power to forbid circumvention of
+technological measures to the extent such circumvention is effected by exercising
+rights under this License with respect to the covered work, and you disclaim any
+intention to limit operation or modification of the work as a means of enforcing,
+against the work's users, your or third parties' legal rights to forbid circumvention
+of technological measures.
+
+### 4. Conveying Verbatim Copies
+
+You may convey verbatim copies of the Program's source code as you receive it, in any
+medium, provided that you conspicuously and appropriately publish on each copy an
+appropriate copyright notice; keep intact all notices stating that this License and
+any non-permissive terms added in accord with section 7 apply to the code; keep
+intact all notices of the absence of any warranty; and give all recipients a copy of
+this License along with the Program.
+
+You may charge any price or no price for each copy that you convey, and you may offer
+support or warranty protection for a fee.
+
+### 5. Conveying Modified Source Versions
+
+You may convey a work based on the Program, or the modifications to produce it from
+the Program, in the form of source code under the terms of section 4, provided that
+you also meet all of these conditions:
+
+- **a)** The work must carry prominent notices stating that you modified it, and giving a
+  relevant date.
+- **b)** The work must carry prominent notices stating that it is released under this
+  License and any conditions added under section 7. This requirement modifies the
+  requirement in section 4 to “keep intact all notices”.
+- **c)** You must license the entire work, as a whole, under this License to anyone who
+  comes into possession of a copy. This License will therefore apply, along with any
+  applicable section 7 additional terms, to the whole of the work, and all its parts,
+  regardless of how they are packaged. This License gives no permission to license the
+  work in any other way, but it does not invalidate such permission if you have
+  separately received it.
+- **d)** If the work has interactive user interfaces, each must display Appropriate Legal
+  Notices; however, if the Program has interactive interfaces that do not display
+  Appropriate Legal Notices, your work need not make them do so.
+
+A compilation of a covered work with other separate and independent works, which are
+not by their nature extensions of the covered work, and which are not combined with
+it such as to form a larger program, in or on a volume of a storage or distribution
+medium, is called an “aggregate” if the compilation and its resulting
+copyright are not used to limit the access or legal rights of the compilation's users
+beyond what the individual works permit. Inclusion of a covered work in an aggregate
+does not cause this License to apply to the other parts of the aggregate.
+
+### 6. Conveying Non-Source Forms
+
+You may convey a covered work in object code form under the terms of sections 4 and
+5, provided that you also convey the machine-readable Corresponding Source under the
+terms of this License, in one of these ways:
+
+- **a)** Convey the object code in, or embodied in, a physical product (including a
+  physical distribution medium), accompanied by the Corresponding Source fixed on a
+  durable physical medium customarily used for software interchange.
+- **b)** Convey the object code in, or embodied in, a physical product (including a
+  physical distribution medium), accompanied by a written offer, valid for at least
+  three years and valid for as long as you offer spare parts or customer support for
+  that product model, to give anyone who possesses the object code either **(1)** a copy of
+  the Corresponding Source for all the software in the product that is covered by this
+  License, on a durable physical medium customarily used for software interchange, for
+  a price no more than your reasonable cost of physically performing this conveying of
+  source, or **(2)** access to copy the Corresponding Source from a network server at no
+  charge.
+- **c)** Convey individual copies of the object code with a copy of the written offer to
+  provide the Corresponding Source. This alternative is allowed only occasionally and
+  noncommercially, and only if you received the object code with such an offer, in
+  accord with subsection 6b.
+- **d)** Convey the object code by offering access from a designated place (gratis or for
+  a charge), and offer equivalent access to the Corresponding Source in the same way
+  through the same place at no further charge. You need not require recipients to copy
+  the Corresponding Source along with the object code. If the place to copy the object
+  code is a network server, the Corresponding Source may be on a different server
+  (operated by you or a third party) that supports equivalent copying facilities,
+  provided you maintain clear directions next to the object code saying where to find
+  the Corresponding Source. Regardless of what server hosts the Corresponding Source,
+  you remain obligated to ensure that it is available for as long as needed to satisfy
+  these requirements.
+- **e)** Convey the object code using peer-to-peer transmission, provided you inform
+  other peers where the object code and Corresponding Source of the work are being
+  offered to the general public at no charge under subsection 6d.
+
+A separable portion of the object code, whose source code is excluded from the
+Corresponding Source as a System Library, need not be included in conveying the
+object code work.
+
+A “User Product” is either **(1)** a “consumer product”, which
+means any tangible personal property which is normally used for personal, family, or
+household purposes, or **(2)** anything designed or sold for incorporation into a
+dwelling. In determining whether a product is a consumer product, doubtful cases
+shall be resolved in favor of coverage. For a particular product received by a
+particular user, “normally used” refers to a typical or common use of
+that class of product, regardless of the status of the particular user or of the way
+in which the particular user actually uses, or expects or is expected to use, the
+product. A product is a consumer product regardless of whether the product has
+substantial commercial, industrial or non-consumer uses, unless such uses represent
+the only significant mode of use of the product.
+
+“Installation Information” for a User Product means any methods,
+procedures, authorization keys, or other information required to install and execute
+modified versions of a covered work in that User Product from a modified version of
+its Corresponding Source. The information must suffice to ensure that the continued
+functioning of the modified object code is in no case prevented or interfered with
+solely because modification has been made.
+
+If you convey an object code work under this section in, or with, or specifically for
+use in, a User Product, and the conveying occurs as part of a transaction in which
+the right of possession and use of the User Product is transferred to the recipient
+in perpetuity or for a fixed term (regardless of how the transaction is
+characterized), the Corresponding Source conveyed under this section must be
+accompanied by the Installation Information. But this requirement does not apply if
+neither you nor any third party retains the ability to install modified object code
+on the User Product (for example, the work has been installed in ROM).
+
+The requirement to provide Installation Information does not include a requirement to
+continue to provide support service, warranty, or updates for a work that has been
+modified or installed by the recipient, or for the User Product in which it has been
+modified or installed. Access to a network may be denied when the modification itself
+materially and adversely affects the operation of the network or violates the rules
+and protocols for communication across the network.
+
+Corresponding Source conveyed, and Installation Information provided, in accord with
+this section must be in a format that is publicly documented (and with an
+implementation available to the public in source code form), and must require no
+special password or key for unpacking, reading or copying.
+
+### 7. Additional Terms
+
+“Additional permissions” are terms that supplement the terms of this
+License by making exceptions from one or more of its conditions. Additional
+permissions that are applicable to the entire Program shall be treated as though they
+were included in this License, to the extent that they are valid under applicable
+law. If additional permissions apply only to part of the Program, that part may be
+used separately under those permissions, but the entire Program remains governed by
+this License without regard to the additional permissions.
+
+When you convey a copy of a covered work, you may at your option remove any
+additional permissions from that copy, or from any part of it. (Additional
+permissions may be written to require their own removal in certain cases when you
+modify the work.) You may place additional permissions on material, added by you to a
+covered work, for which you have or can give appropriate copyright permission.
+
+Notwithstanding any other provision of this License, for material you add to a
+covered work, you may (if authorized by the copyright holders of that material)
+supplement the terms of this License with terms:
+
+- **a)** Disclaiming warranty or limiting liability differently from the terms of
+  sections 15 and 16 of this License; or
+- **b)** Requiring preservation of specified reasonable legal notices or author
+  attributions in that material or in the Appropriate Legal Notices displayed by works
+  containing it; or
+- **c)** Prohibiting misrepresentation of the origin of that material, or requiring that
+  modified versions of such material be marked in reasonable ways as different from the
+  original version; or
+- **d)** Limiting the use for publicity purposes of names of licensors or authors of the
+  material; or
+- **e)** Declining to grant rights under trademark law for use of some trade names,
+  trademarks, or service marks; or
+- **f)** Requiring indemnification of licensors and authors of that material by anyone
+  who conveys the material (or modified versions of it) with contractual assumptions of
+  liability to the recipient, for any liability that these contractual assumptions
+  directly impose on those licensors and authors.
+
+All other non-permissive additional terms are considered “further
+restrictions” within the meaning of section 10. If the Program as you received
+it, or any part of it, contains a notice stating that it is governed by this License
+along with a term that is a further restriction, you may remove that term. If a
+license document contains a further restriction but permits relicensing or conveying
+under this License, you may add to a covered work material governed by the terms of
+that license document, provided that the further restriction does not survive such
+relicensing or conveying.
+
+If you add terms to a covered work in accord with this section, you must place, in
+the relevant source files, a statement of the additional terms that apply to those
+files, or a notice indicating where to find the applicable terms.
+
+Additional terms, permissive or non-permissive, may be stated in the form of a
+separately written license, or stated as exceptions; the above requirements apply
+either way.
+
+### 8. Termination
+
+You may not propagate or modify a covered work except as expressly provided under
+this License. Any attempt otherwise to propagate or modify it is void, and will
+automatically terminate your rights under this License (including any patent licenses
+granted under the third paragraph of section 11).
+
+However, if you cease all violation of this License, then your license from a
+particular copyright holder is reinstated **(a)** provisionally, unless and until the
+copyright holder explicitly and finally terminates your license, and **(b)** permanently,
+if the copyright holder fails to notify you of the violation by some reasonable means
+prior to 60 days after the cessation.
+
+Moreover, your license from a particular copyright holder is reinstated permanently
+if the copyright holder notifies you of the violation by some reasonable means, this
+is the first time you have received notice of violation of this License (for any
+work) from that copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+Termination of your rights under this section does not terminate the licenses of
+parties who have received copies or rights from you under this License. If your
+rights have been terminated and not permanently reinstated, you do not qualify to
+receive new licenses for the same material under section 10.
+
+### 9. Acceptance Not Required for Having Copies
+
+You are not required to accept this License in order to receive or run a copy of the
+Program. Ancillary propagation of a covered work occurring solely as a consequence of
+using peer-to-peer transmission to receive a copy likewise does not require
+acceptance. However, nothing other than this License grants you permission to
+propagate or modify any covered work. These actions infringe copyright if you do not
+accept this License. Therefore, by modifying or propagating a covered work, you
+indicate your acceptance of this License to do so.
+
+### 10. Automatic Licensing of Downstream Recipients
+
+Each time you convey a covered work, the recipient automatically receives a license
+from the original licensors, to run, modify and propagate that work, subject to this
+License. You are not responsible for enforcing compliance by third parties with this
+License.
+
+An “entity transaction” is a transaction transferring control of an
+organization, or substantially all assets of one, or subdividing an organization, or
+merging organizations. If propagation of a covered work results from an entity
+transaction, each party to that transaction who receives a copy of the work also
+receives whatever licenses to the work the party's predecessor in interest had or
+could give under the previous paragraph, plus a right to possession of the
+Corresponding Source of the work from the predecessor in interest, if the predecessor
+has it or can get it with reasonable efforts.
+
+You may not impose any further restrictions on the exercise of the rights granted or
+affirmed under this License. For example, you may not impose a license fee, royalty,
+or other charge for exercise of rights granted under this License, and you may not
+initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging
+that any patent claim is infringed by making, using, selling, offering for sale, or
+importing the Program or any portion of it.
+
+### 11. Patents
+
+A “contributor” is a copyright holder who authorizes use under this
+License of the Program or a work on which the Program is based. The work thus
+licensed is called the contributor's “contributor version”.
+
+A contributor's “essential patent claims” are all patent claims owned or
+controlled by the contributor, whether already acquired or hereafter acquired, that
+would be infringed by some manner, permitted by this License, of making, using, or
+selling its contributor version, but do not include claims that would be infringed
+only as a consequence of further modification of the contributor version. For
+purposes of this definition, “control” includes the right to grant patent
+sublicenses in a manner consistent with the requirements of this License.
+
+Each contributor grants you a non-exclusive, worldwide, royalty-free patent license
+under the contributor's essential patent claims, to make, use, sell, offer for sale,
+import and otherwise run, modify and propagate the contents of its contributor
+version.
+
+In the following three paragraphs, a “patent license” is any express
+agreement or commitment, however denominated, not to enforce a patent (such as an
+express permission to practice a patent or covenant not to sue for patent
+infringement). To “grant” such a patent license to a party means to make
+such an agreement or commitment not to enforce a patent against the party.
+
+If you convey a covered work, knowingly relying on a patent license, and the
+Corresponding Source of the work is not available for anyone to copy, free of charge
+and under the terms of this License, through a publicly available network server or
+other readily accessible means, then you must either **(1)** cause the Corresponding
+Source to be so available, or **(2)** arrange to deprive yourself of the benefit of the
+patent license for this particular work, or **(3)** arrange, in a manner consistent with
+the requirements of this License, to extend the patent license to downstream
+recipients. “Knowingly relying” means you have actual knowledge that, but
+for the patent license, your conveying the covered work in a country, or your
+recipient's use of the covered work in a country, would infringe one or more
+identifiable patents in that country that you have reason to believe are valid.
+
+If, pursuant to or in connection with a single transaction or arrangement, you
+convey, or propagate by procuring conveyance of, a covered work, and grant a patent
+license to some of the parties receiving the covered work authorizing them to use,
+propagate, modify or convey a specific copy of the covered work, then the patent
+license you grant is automatically extended to all recipients of the covered work and
+works based on it.
+
+A patent license is “discriminatory” if it does not include within the
+scope of its coverage, prohibits the exercise of, or is conditioned on the
+non-exercise of one or more of the rights that are specifically granted under this
+License. You may not convey a covered work if you are a party to an arrangement with
+a third party that is in the business of distributing software, under which you make
+payment to the third party based on the extent of your activity of conveying the
+work, and under which the third party grants, to any of the parties who would receive
+the covered work from you, a discriminatory patent license **(a)** in connection with
+copies of the covered work conveyed by you (or copies made from those copies), or **(b)**
+primarily for and in connection with specific products or compilations that contain
+the covered work, unless you entered into that arrangement, or that patent license
+was granted, prior to 28 March 2007.
+
+Nothing in this License shall be construed as excluding or limiting any implied
+license or other defenses to infringement that may otherwise be available to you
+under applicable patent law.
+
+### 12. No Surrender of Others' Freedom
+
+If conditions are imposed on you (whether by court order, agreement or otherwise)
+that contradict the conditions of this License, they do not excuse you from the
+conditions of this License. If you cannot convey a covered work so as to satisfy
+simultaneously your obligations under this License and any other pertinent
+obligations, then as a consequence you may not convey it at all. For example, if you
+agree to terms that obligate you to collect a royalty for further conveying from
+those to whom you convey the Program, the only way you could satisfy both those terms
+and this License would be to refrain entirely from conveying the Program.
+
+### 13. Use with the GNU Affero General Public License
+
+Notwithstanding any other provision of this License, you have permission to link or
+combine any covered work with a work licensed under version 3 of the GNU Affero
+General Public License into a single combined work, and to convey the resulting work.
+The terms of this License will continue to apply to the part which is the covered
+work, but the special requirements of the GNU Affero General Public License, section
+13, concerning interaction through a network will apply to the combination as such.
+
+### 14. Revised Versions of this License
+
+The Free Software Foundation may publish revised and/or new versions of the GNU
+General Public License from time to time. Such new versions will be similar in spirit
+to the present version, but may differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Program specifies that
+a certain numbered version of the GNU General Public License “or any later
+version” applies to it, you have the option of following the terms and
+conditions either of that numbered version or of any later version published by the
+Free Software Foundation. If the Program does not specify a version number of the GNU
+General Public License, you may choose any version ever published by the Free
+Software Foundation.
+
+If the Program specifies that a proxy can decide which future versions of the GNU
+General Public License can be used, that proxy's public statement of acceptance of a
+version permanently authorizes you to choose that version for the Program.
+
+Later license versions may give you additional or different permissions. However, no
+additional obligations are imposed on any author or copyright holder as a result of
+your choosing to follow a later version.
+
+### 15. Disclaimer of Warranty
+
+THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
+EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER
+EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE
+QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
+DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+### 16. Limitation of Liability
+
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY
+COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS
+PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,
+INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
+PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE
+OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE
+WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+### 17. Interpretation of Sections 15 and 16
+
+If the disclaimer of warranty and limitation of liability provided above cannot be
+given local legal effect according to their terms, reviewing courts shall apply local
+law that most closely approximates an absolute waiver of all civil liability in
+connection with the Program, unless a warranty or assumption of liability accompanies
+a copy of the Program in return for a fee.
+
+_END OF TERMS AND CONDITIONS_
+
+## How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest possible use to
+the public, the best way to achieve this is to make it free software which everyone
+can redistribute and change under these terms.
+
+To do so, attach the following notices to the program. It is safest to attach them
+to the start of each source file to most effectively state the exclusion of warranty;
+and each file should have at least the “copyright” line and a pointer to
+where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program does terminal interaction, make it output a short notice like this
+when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type 'show c' for details.
+
+The hypothetical commands `show w` and `show c` should show the appropriate parts of
+the General Public License. Of course, your program's commands might be different;
+for a GUI interface, you would use an “about box”.
+
+You should also get your employer (if you work as a programmer) or school, if any, to
+sign a “copyright disclaimer” for the program, if necessary. For more
+information on this, and how to apply and follow the GNU GPL, see
+&lt;<http://www.gnu.org/licenses/>&gt;.
+
+The GNU General Public License does not permit incorporating your program into
+proprietary programs. If your program is a subroutine library, you may consider it
+more useful to permit linking proprietary applications with the library. If this is
+what you want to do, use the GNU Lesser General Public License instead of this
+License. But first, please read
+&lt;<http://www.gnu.org/philosophy/why-not-lgpl.html>&gt;.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sterling"
-version = "0.1.0"
+version = "1.0.1"
 description = "Converts a given D&D 5e currency value to the Silver Standard."
 authors = ["Zachary Dziura <zcdziura@gmail.com>"]
 readme = "README.md"
@@ -8,10 +8,31 @@ license = "Unlicense/MIT"
 repository = "https://gitlab.com/zcdziura/sterling"
 keywords = ["dnd", "coins", "converter", "currency", "5e"]
 
+[lib]
+name = "sterling_ops"
+path = "src/lib.rs"
+
+[[bin]]
+name = "sterling"
+path = "src/main.rs"
+
 [dependencies]
-clap = "2.31.1"
-lazy_static = "1.0.0"
-regex = "0.2"
+clap = "2.32"
+lazysort = "0.2"
+lazy_static = "1.0"
+regex = "1.0"
+separator = "0.3"
+serde = "1.0"
+serde_derive = "1.0"
+serde_yaml = "0.7"
+
+[dev-dependencies]
+criterion = "0.2"
 
 [profile.release]
-lto = true
+lto = true
+panic = "abort"
+
+[[bench]]
+name = "bench"
+harness = false

MIT.md

@@ -1,26 +0,0 @@
-The MIT License (MIT)
-=====================
-
-Copyright © `<year>` `<copyright holders>`
-
-Permission is hereby granted, free of charge, to any person
-obtaining a copy of this software and associated documentation
-files (the “Software”), to deal in the Software without
-restriction, including without limitation the rights to use,
-copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the
-Software is furnished to do so, subject to the following
-conditions:
-
-The above copyright notice and this permission notice shall be
-included in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND,
-EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
-OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
-HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
-WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-OTHER DEALINGS IN THE SOFTWARE.
-

README.md

@@ -1,67 +1,182 @@
 # Sterling
 
-Converts a given D&D 5e currency value to the Silver Standard. Inspired by the Reddit posts titled
-[The Silver Hack: Making Money Matter](https://www.reddit.com/r/DnDBehindTheScreen/comments/80f6kt/the_silver_hack_making_money_matter/),
-and [I make Silver Standard for 5th Edition (Spreadsheets.)](https://www.reddit.com/r/dndnext/comments/5tt5g8/i_make_silver_standard_for_5_edition_spreadsheets/).
+Converts a given D&D 5e currency value to the Silver Standard. Inspired by the
+Reddit posts titled [The Silver Hack: Making Money
+Matter](https://www.reddit.com/r/DnDBehindTheScreen/comments/80f6kt/the_silver_hack_making_money_matter/),
+and [I make Silver Standard for 5th Edition
+(Spreadsheets.)](https://www.reddit.com/r/dndnext/comments/5tt5g8/i_make_silver_standard_for_5_edition_spreadsheets/).
 
 ## Usage
 
 ```
-sterling [VALUE]...
+USAGE:
+    sterling [FLAGS] [OPTIONS] [VALUE]... [SUBCOMMAND]
 
 FLAGS:
-    -h, --help       Prints help information
-    -V, --version    Prints version information
+    -o, --optional    Include currencies marked as optional when converting
+    -f, --full        Print currencies with their full name, rather than with their alias
+    -h, --help        Prints help information
+    -V, --version     Prints version information
+
+OPTIONS:
+    -c, --config <CONFIG>    Specify location of config file; defaults to './sterling-conf.yml'.
 
 ARGS:
-    <VALUE>...    The value to be converted; should be suffixed with the coin's short-hand
-                  abbreviation, i.e. p, g, e, s, or c. Defaults coin type to 'g'.
+    <VALUE>...    The value to be converted; should be suffixed with the coin's short-hand abbreviation, i.e. p, g,
+                  e, s, or c.
+
+SUBCOMMANDS:
+    add       Add two currency amounts together; uses the currencies defined in your config file
+    copper    Calculate the copper value of a custom currency
+    div       Divide a currency amount by some scalar divisor; uses the currencies defined in your config file
+    help      Prints this message or the help of the given subcommand(s)
+    mul       Multiply a scalar multiplicand by a currency amount; uses the currencies defined in your config file
+    sub       Subtract two currency amounts from one another; uses the currencies defined in your config file
 ```
 
-## Examples
+## Converting Currency Examples
 
 ```
-// Convert one hundred platinum coins: 
+// Convert one hundred platinum coins:
 sterling 100p // 10g
 
 // Convert one hundred platinum, fifty gold coins:
-sterling 100p 50g // 10g 5s
+sterling 100p 50g // 10g, 50s
 
-// Convert fifteen thousand copper coins:
-sterling 15000c // 1g 50s
+// Convert fifteen thousand copper coins, printing the full names of the coins:
+sterling -f 15000c // 1 gold, 50 silvers
 
 // Convert one platinum, thirty-six gold, twelve electrum, eighty-two silver, and four hundred
-// sixty-nine copper coins
-sterling 1p 36g 12e 82s 469c // 64s 89c
+// sixty-nine copper coins, printing the full names of the coins
+sterling --full 1p 36g 12e 82s 469c // 64 silvers, 89 coppers
+
+// Convert one platinum, thirty-six gold, twelve electrum, eighty-two silver, and four hundred
+// sixty-nine copper coins, printing the full names of the coins, using the custom config file
+// detailed below, including optional currencies
+sterling --full -o -c "~/Documents/D&D/sterling-conf.yml" 1p 36g 12e 82s 469c // 7 guilders, 6 sterling, 25 pence
 ```
 
+## Subcommand Examples
+
+```
+// Add together ten and twenty pense, using the custom config file detailed below
+sterling add "10p" "20p" // 30p
+
+// Subtract two sterling and ten pence from one eagle
+sterling --full sub "1e" "2s 10p" // 19 guilders, 25 sterling, 22 pence
+
+// Subtract one eagle from two sterling and ten pence. Note that, regardless of order, the smaller
+// value is ALWAYS subtracted from the larger value.
+sterling --full sub "2s 10p" "1F" // 19 guilders, 25 sterling, 22 pence
+
+// Multiply two sterling and ten pence by thirteen. Note that the currencies always go after the
+// multiplier.
+sterling --full mul 13 2s 10p // 1 guilder, 2 sterling, 2 pence
+
+// Divide one guilder, 2 sterling, and 2 pence by thirteen.
+sterling --full div 13 1g 2s 2p // 2 sterling, 10 pence
+
+// Convert one note, three eagles, and five guilders into copper
+sterling copper 1N 3e 5g // 201,600c
+```
+
+Note that `sterling` doesn't allow for negative currencies. Therefore, when
+subtracting currencies, the smaller currency value will always be subtracted
+from the larger currency value, regardless of the order of the currencies in the
+`sub` command.
+
+## Custom Currencies
+
+`sterling` allows for user-defined currencies, with their own names and
+conversion rates. By default, `sterling` will look at a file within the current
+directory called `sterling-conf.yml`, or in whatever location as supplied by the
+`-c` flag. You can also specify that a currency be optional, which will prevent
+that currency from being used when converting values, unless the `-o` flag is
+passed. Below is an example `sterling-conf.yml` file, showing the actual
+currencies that I use within my own campaign!
+
+```
+-
+  name: "note"
+  rate: 143360
+  alias: "N"
+  optional: true
+-
+  name: "eagle"
+  rate: 17920
+  alias: "e"
+-
+  name: "guilder"
+  rate: 896
+  alias: "g"
+-
+  name: "shilling"
+  rate: 32
+  alias: "s"
+  plural: "sterling"
+-
+  name: "penny"
+  rate: 1
+  alias: "p"
+  plural: "pence"
+```
+
+Please note that the `rate` value is defined as the number of copper coins that
+goes into one of that particular currency. In the example above, thirty-two
+copper coins goes into one "shilling", and eight-hundred ninety-siz copper coins
+goes into one "guilder".
+
 ## Abstract
 
-Items and expenses are, by default, assigned arbitrary currency values within the official D&D 5th
-edition source books. Many of the officially priced items use the "Gold Standard"; that is, items
-are priced in gold coins by default. While there is nothing wrong with using official currency
-values within your campaign, it leads to the perceived value of gold to be less in the eyes of your
-players. Gold has been sought after as both a commodity and a currency for centuries, and your
-campaign aught to treat gold similarly!
+Items and expenses are, by default, assigned arbitrary currency values within
+the official D&D 5th edition source books. Many of the officially priced items
+use the "Gold Standard"; that is, items are priced in gold coins by default.
+While there is nothing wrong with using official currency values within your
+campaign, it leads to the perceived value of gold to be less in the eyes of your
+players. Gold has been sought after as both a commodity and a currency for
+centuries, and your campaign aught to treat gold similarly!
 
 ## Explanation
 
-The basis of the Silver Standard treats 1 gold coin from the official D&D 5e source books as 1
-silver coin, and that there are one hundred of a given coin to every one of the next highest valued
-coin. That's all. Thus, one hundred fifty copper coins equals one silver and fifty copper coins,
-while a suit of heavy plate armor equals fifteen gold coins, rather than fifteen hundred.
+The basis of the Silver Standard treats one gold coin from the official D&D 5e
+source books as one silver coin, and that there are one hundred of a given coin
+to every one of the next highest valued coin. That's all. Thus, one hundred
+fifty copper coins equals one silver and fifty copper coins, while a suit of
+heavy plate armor equals fifteen gold coins, rather than fifteen hundred.
 
 ## Installation
 
-Make sure that you first have `rust` and `cargo` installed onto your computer before downloading
-`sterling`. Just follow the simple
-[Installation Guide](https://doc.rust-lang.org/cargo/getting-started/installation.html) on the
-official Rust language website to install both programs.
+The easiest way to install `sterling` is to do so with `cargo`, the build tool
+that's installed along with the `rust` compiler. If you already have `rust` and
+`cargo` installed onto your computer, simply run the following command from a
+command prompt:
 
-Once `rust` and `cargo` are installed onto your computer, run the following command:
+```
+$ cargo install sterling
+```
 
-`cargo install sterling`
+If you do not have the `rust` compiler installed, you can also find pre-built
+binaries for 64-bit Windows, macOS, and Linux computers in the "Tags" navigation
+link, which is displayed above this README. Simply download the correct binary
+for your computer's operating system, extract it somewhere into your file system
+(such as a "bin" folder within your user directory), and add that location to
+your system's PATH.
 
-This will install `sterling` into the `.cargo/bin` directory within your User directory
-(`/home/YOUR_USER_NAME` on Linux and macOS, `C:\Users\YOUR_USER_NAME` on Windows). Be sure to add
-this directory to your PATH.
+## License
+
+```
+Copyright (C) 2018-2022 Z. Charles Dziura
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+```

UNLICENSE.md

@@ -1,27 +0,0 @@
-Unlicense (Public Domain)
-============================
-
-This is free and unencumbered software released into the public domain.
-
-Anyone is free to copy, modify, publish, use, compile, sell, or
-distribute this software, either in source code form or as a compiled
-binary, for any purpose, commercial or non-commercial, and by any
-means.
-
-In jurisdictions that recognize copyright laws, the author or authors
-of this software dedicate any and all copyright interest in the
-software to the public domain. We make this dedication for the benefit
-of the public at large and to the detriment of our heirs and
-successors. We intend this dedication to be an overt act of
-relinquishment in perpetuity of all present and future rights to this
-software under copyright law.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
-OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
-ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-OTHER DEALINGS IN THE SOFTWARE.
-
-For more information, please refer to &lt;<http://unlicense.org/>&gt;

WAIVER.sigs

@@ -1,24 +0,0 @@
------BEGIN PGP SIGNED MESSAGE-----
-Hash: SHA256
-
-I dedicate any and all copyright interest in this software to the
-public domain. I make this dedication for the benefit of the public at
-large and to the detriment of my heirs and successors. I intend this
-dedication to be an overt act of relinquishment in perpetuity of all
-present and future rights to this software under copyright law.
------BEGIN PGP SIGNATURE-----
-
-iQIzBAEBCAAdFiEEMqo2ba6LuiYDXB5kdkVeHsxAMfYFAlqjHbsACgkQdkVeHsxA
-MfZy5hAAoSrAqT7Mm3d/r0rRuVTTotvZye6PgKdIx+XSdAYVeRjFrtOumldEDq84
-peE9JjunmfUxqvYPmk8CC6gzdVkkHNh0MM4WHop/qoQGwSQD36G5TvnTEc2SjIYd
-NVHbTCz8MpIJ8wzn2EH5x8S3BWIy7XB3NJhIuPBsJzSUSniP5d4J3tJw/2hiO34E
-PaKGSfLk9fAErgXUk+PEn98dXuPHeyrFYsSRQZP5yiTlH7eVloe8VTFIjUF+P0qA
-XrHWKaEVQYWPXMBTpF8pfPg4rFVnu7F7Pl145AAmQJJo45VLmfDBNWAGQHYMXoyZ
-bsCd9hQ9zhZMSXi7CBwMQc6itTKVetv1vH0DB77RLfOs+flvqASV1v1mhgBuxWIy
-E0XzMcR1LtSPu9bdNxc/ClDGbFe5NfZU+dbUqTmpPZBgvfF0I/N/hw5RuDusS+hF
-m0uvyRL0xIKIgTcNKgfU6pMe4gzVyPCqJ13kJVHfh7RFQ0MV7eQ3eowf8JDnrYZY
-8DHJpnLxXKLfPeLY73iQFifFSFPjvpD5ObbDcXMZYToaC39d1n6MtUkh0o5aF8L4
-sA9OGScTevQN9U4bO6AcaUXkqrHuQ9mIk+oP2w1e44O/Fwo9UoBNK0Quc7yA86KJ
-tnDsTCZNW9HnwuZvXOuLaUEtWP0DYWDmsQmuIhT5VPAhGp7nv0s=
-=2YGI
------END PGP SIGNATURE-----

appveyor.yml

@@ -0,0 +1,60 @@
+# Based on the "trust" template v0.1.2
+# https://github.com/japaric/trust/tree/v0.1.2
+
+environment:
+  global:
+    RUST_VERSION: stable
+    CRATE_NAME: sterling
+    
+  matrix:
+    # MinGW
+    - TARGET: x86_64-pc-windows-gnu
+
+install:
+  - ps: >-
+      If ($Env:TARGET -eq 'x86_64-pc-windows-gnu') {
+        $Env:PATH += ';C:\msys64\mingw64\bin'
+      } ElseIf ($Env:TARGET -eq 'i686-pc-windows-gnu') {
+        $Env:PATH += ';C:\msys64\mingw32\bin'
+      }
+  - curl -sSf -o rustup-init.exe https://win.rustup.rs/
+  - rustup-init.exe -y --default-host %TARGET% --default-toolchain %RUST_VERSION%
+  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
+  - rustc -Vv
+  - cargo -V
+
+test_script:
+  # we don't run the "test phase" when doing deploys
+  - if [%APPVEYOR_REPO_TAG%]==[true] (
+      cargo test --target %TARGET% &&
+      cargo build --target %TARGET% --release
+    )
+
+before_deploy:
+  - ps: ci\before_deploy.ps1
+
+deploy:
+  artifact: /.*\.zip/
+  auth_token:
+    secure: bvA/4J1T0h65ur6tsg6k/wlZFjP3qr2QsyRsmGMEmm7DOF61xmzTnjuBcPjQYrba
+  on:
+    RUST_VERSION: stable
+    appveyor_repo_tag: true
+  provider: GitHub
+
+cache:
+  - C:\Users\appveyor\.cargo\registry
+  - target
+
+branches:
+  only:
+    # Release tags
+    - /^v\d+\.\d+\.\d+.*$/
+    # - master
+
+notifications:
+  - provider: Email
+    on_build_success: false
+
+# Building is done in the test phase, so we disable Appveyor's build phase.
+build: false

benches/bench.rs

@@ -0,0 +1,27 @@
+#[macro_use]
+extern crate criterion;
+#[macro_use]
+extern crate lazy_static;
+extern crate sterling_ops;
+
+use criterion::Criterion;
+use sterling_ops::currency::Currency;
+use sterling_ops::*;
+
+lazy_static! {
+    static ref CURRENCIES: Vec<Currency> = vec![
+        Currency::new("penny", 1, "p", Some("pence".to_owned()), None),
+        Currency::new("shilling", 100, "s", Some("sterling".to_owned()), None),
+        Currency::new("guilder", 10_000, "g", None, None),
+        Currency::new("note", 1_000_000, "N", None, Some(true)),
+    ];
+}
+
+fn criterion_benchmark(c: &mut Criterion) {
+    c.bench_function("default operation", |b| {
+        b.iter(|| default_operation("3p 5s 7s 132c", &CURRENCIES, true))
+    });
+}
+
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);

ci/before_deploy.ps1

@@ -0,0 +1,22 @@
+# This script takes care of packaging the build artifacts that will go in the
+# release zipfile
+
+$SRC_DIR = $PWD.Path
+$STAGE = [System.Guid]::NewGuid().ToString()
+
+Set-Location $ENV:Temp
+New-Item -Type Directory -Name $STAGE
+Set-Location $STAGE
+
+$ZIP = "$SRC_DIR\$($Env:CRATE_NAME)-$($Env:APPVEYOR_REPO_TAG_NAME)-$($Env:TARGET).zip"
+
+Copy-Item "$SRC_DIR\target\$($Env:TARGET)\release\sterling.exe" '.\'
+
+7z a "$ZIP" *
+
+Push-AppveyorArtifact "$ZIP"
+
+Remove-Item *.* -Force
+Set-Location ..
+Remove-Item $STAGE
+Set-Location $SRC_DIR

ci/before_deploy.sh

@@ -0,0 +1,32 @@
+# This script takes care of building your crate and packaging it for release
+
+set -ex
+
+main() {
+    local src=$(pwd) \
+          stage=
+
+    case $TRAVIS_OS_NAME in
+        linux)
+            stage=$(mktemp -d)
+            ;;
+        osx)
+            stage=$(mktemp -d -t tmp)
+            ;;
+    esac
+
+    test -f Cargo.lock || cargo generate-lockfile
+
+    cargo build --release --target $TARGET
+
+    # TODO Update this to package the right artifacts
+    cp target/$TARGET/release/sterling $stage/
+
+    cd $stage
+    tar czf $src/$CRATE_NAME-$TRAVIS_TAG-$TARGET.tar.gz *
+    cd $src
+
+    rm -rf $stage
+}
+
+main

ci/install.sh

@@ -0,0 +1,14 @@
+set -ex
+
+main() {
+    local target=
+    if [ $TRAVIS_OS_NAME = linux ]; then
+        target=x86_64-unknown-linux-gnu
+        sort=sort
+    else
+        target=x86_64-apple-darwin
+        sort=gsort  # for `sort --sort-version`, from brew's coreutils.
+    fi
+}
+
+main

ci/script.sh

@@ -0,0 +1,18 @@
+# This script takes care of testing your crate
+
+set -ex
+
+main() {
+    cross build --target $TARGET --release
+
+    if [ ! -z $DISABLE_TESTS ]; then
+        return
+    fi
+
+    cross test --target $TARGET
+}
+
+# we don't run the "test phase" when doing deploys
+if [ -z $TRAVIS_TAG ]; then
+    main
+fi

src/config.rs

@@ -0,0 +1,93 @@
+use std::convert::From;
+use std::error::Error;
+use std::fmt::{self, Display, Formatter};
+use std::fs::File;
+use std::io::{self, BufReader, ErrorKind};
+
+use serde_yaml;
+
+use currency::Currency;
+
+pub fn load_config(filename: &str) -> Result<Vec<Currency>, ConfigError> {
+    let config_file = File::open(filename)?;
+    let config: Vec<Currency> = serde_yaml::from_reader(BufReader::new(config_file))?;
+
+    Ok(config)
+}
+
+pub fn parse_currency_config(
+    config_result: Result<Vec<Currency>, ConfigError>,
+    config_file_path: Option<&str>,
+) -> Result<Vec<Currency>, String> {
+    match config_result {
+        Ok(values) => Ok(values),
+        Err(error) => match error.kind {
+            ErrorKind::NotFound => {
+                if let Some(file_path) = config_file_path {
+                    Err(format!(
+                        "Sterling Error: Can't find configuration file: \"{}\"",
+                        &file_path
+                    ))
+                } else {
+                    Ok(silver_standard_config())
+                }
+            }
+            _ => Err(format!("Sterling Error: {}", error)),
+        },
+    }
+}
+
+pub fn phb_config() -> Vec<Currency> {
+    vec![
+        Currency::new("platinum", 1000, "p", None, None),
+        Currency::new("gold", 100, "g", None, None),
+        Currency::new("electrum", 50, "e", None, Some(true)),
+        Currency::new("silver", 10, "s", None, None),
+        Currency::new("copper", 1, "c", None, None),
+    ]
+}
+
+fn silver_standard_config() -> Vec<Currency> {
+    vec![
+        Currency::new("platinum", 1_000_000, "p", None, None),
+        Currency::new("gold", 10_000, "g", None, None),
+        Currency::new("silver", 100, "s", None, None),
+        Currency::new("copper", 1, "c", None, None),
+    ]
+}
+
+#[derive(Debug)]
+pub struct ConfigError {
+    desc: String,
+    pub kind: ErrorKind,
+}
+
+impl Display for ConfigError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "Sterling Error: {}", self.desc)
+    }
+}
+
+impl Error for ConfigError {
+    fn description(&self) -> &str {
+        &self.desc
+    }
+}
+
+impl From<io::Error> for ConfigError {
+    fn from(error: io::Error) -> Self {
+        ConfigError {
+            desc: error.description().to_owned(),
+            kind: error.kind(),
+        }
+    }
+}
+
+impl From<serde_yaml::Error> for ConfigError {
+    fn from(error: serde_yaml::Error) -> Self {
+        ConfigError {
+            desc: error.description().to_owned(),
+            kind: ErrorKind::Other,
+        }
+    }
+}

src/convert.rs

@@ -0,0 +1,109 @@
+use std::collections::HashMap;
+use std::str::FromStr;
+
+use regex::Regex;
+use separator::Separatable;
+
+use currency::Currency;
+use lazysort::Sorted;
+
+pub fn calculate_total_copper_value(
+    values: &str,
+    currency_regex: &Regex,
+    rates: HashMap<String, usize>,
+) -> usize {
+    currency_regex
+        .captures_iter(&values)
+        .fold(0, |sum, capture| {
+            let value: usize = str::replace(&capture[1], ",", "").parse().unwrap();
+            let rate: &usize = rates.get(&capture[2]).unwrap();
+            let product = value * rate;
+
+            sum + product
+        })
+}
+
+pub fn exchange_currencies(
+    copper_value: usize,
+    currencies: &[Currency],
+    print_full_name: bool,
+) -> Vec<String> {
+    let mut val = copper_value;
+    currencies
+        .iter()
+        .sorted()
+        .filter(|currency| currency.optional.unwrap_or(true))
+        .map(|currency| {
+            let value = val / currency.rate;
+            val = val % currency.rate;
+
+            (
+                value,
+                if print_full_name {
+                    if value > 1 {
+                        match (&currency).plural {
+                            Some(ref plural) => String::from_str(plural).unwrap(),
+                            None => format!("{}s", &currency.name),
+                        }
+                    } else {
+                        String::from_str(&currency.name).unwrap()
+                    }
+                } else {
+                    String::from_str(&currency.alias).unwrap()
+                },
+            )
+        })
+        .filter(|tuple| tuple.0 > 0)
+        .map(|tuple| {
+            format!(
+                "{}{}{}",
+                tuple.0.separated_string(),
+                if tuple.1.len() > 1 { " " } else { "" },
+                tuple.1
+            )
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashMap;
+
+    use super::{calculate_total_copper_value, exchange_currencies};
+    use currency::Currency;
+    use regex::Regex;
+
+    lazy_static! {
+        static ref STANDARD_CURRENCIES: Vec<Currency> = vec![
+            Currency::new("guilder", 10_000, "g", None, None),
+            Currency::new("shilling", 100, "s", Some("sterling".to_owned()), None),
+            Currency::new("penny", 1, "p", Some("pence".to_owned()), None),
+        ];
+        static ref CURRENCY_REGEX: Regex = Regex::new(r"(\d+)([Ngsp])").unwrap();
+    }
+
+    #[test]
+    fn test_calculate_total_copper_value() {
+        let rates: HashMap<String, usize> = vec![
+            ("g".to_owned(), 10_000usize),
+            ("s".to_owned(), 100usize),
+            ("p".to_owned(), 1usize),
+        ].into_iter()
+            .collect();
+
+        let result = 10101usize;
+        assert_eq!(
+            result,
+            calculate_total_copper_value("1g 1s 1p", &CURRENCY_REGEX, rates)
+        );
+    }
+
+    #[test]
+    fn test_exchange_currencies() {
+        let result = vec!["1g".to_owned(), "1s".to_owned(), "1p".to_owned()];
+        assert_eq!(
+            result,
+            exchange_currencies(10101, &STANDARD_CURRENCIES, false)
+        );
+    }
+}

src/currency.rs

@@ -0,0 +1,53 @@
+use std::cmp::Ordering;
+
+#[derive(Clone, Debug, Eq, Serialize, Deserialize)]
+pub struct Currency {
+    pub name: String,
+    pub rate: usize,
+    pub alias: String,
+    pub plural: Option<String>,
+    pub optional: Option<bool>,
+}
+
+impl Currency {
+    pub fn new(
+        name: &str,
+        rate: usize,
+        alias: &str,
+        plural: Option<String>,
+        optional: Option<bool>,
+    ) -> Currency {
+        Currency {
+            name: name.to_owned(),
+            rate,
+            alias: alias.to_owned(),
+            plural,
+            optional,
+        }
+    }
+
+    pub fn is_optional(&self) -> bool {
+        match self.optional {
+            Some(optional) => optional,
+            None => false,
+        }
+    }
+}
+
+impl Ord for Currency {
+    fn cmp(&self, other: &Currency) -> Ordering {
+        other.rate.cmp(&self.rate)
+    }
+}
+
+impl PartialOrd for Currency {
+    fn partial_cmp(&self, other: &Currency) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl PartialEq for Currency {
+    fn eq(&self, other: &Currency) -> bool {
+        self.rate == other.rate
+    }
+}

src/lib.rs

@@ -0,0 +1,244 @@
+extern crate lazysort;
+#[allow(unused_imports)]
+#[macro_use]
+extern crate lazy_static;
+extern crate regex;
+extern crate separator;
+extern crate serde;
+#[macro_use]
+extern crate serde_derive;
+extern crate serde_yaml;
+
+use std::collections::HashMap;
+
+pub mod config;
+mod convert;
+pub mod currency;
+
+use currency::Currency;
+use regex::Regex;
+use separator::Separatable;
+
+pub fn add_operation(
+    augend: &str,
+    addend: &str,
+    custom_currency_regex: &Regex,
+    currencies: &[Currency],
+    print_full: bool,
+) -> String {
+    let lhs =
+        convert::calculate_total_copper_value(augend, custom_currency_regex, get_rates(currencies));
+
+    let rhs = convert::calculate_total_copper_value(
+        addend,
+        &custom_currency_regex,
+        get_rates(currencies.as_ref()),
+    );
+
+    convert::exchange_currencies(lhs + rhs, currencies, print_full).join(", ")
+}
+
+pub fn sub_operation(
+    minuend: &str,
+    subtrahend: &str,
+    custom_currency_regex: &Regex,
+    currencies: &[Currency],
+    print_full: bool,
+) -> String {
+    let lhs = convert::calculate_total_copper_value(
+        minuend,
+        custom_currency_regex,
+        get_rates(currencies),
+    );
+
+    let rhs = convert::calculate_total_copper_value(
+        subtrahend,
+        custom_currency_regex,
+        get_rates(currencies),
+    );
+
+    let difference = if lhs > rhs { lhs - rhs } else { rhs - lhs };
+    convert::exchange_currencies(difference, currencies, print_full).join(", ")
+}
+
+pub fn mul_operation(
+    multiplicand: &str,
+    multiplier: usize,
+    custom_currency_regex: &Regex,
+    currencies: &[Currency],
+    print_full: bool,
+) -> String {
+    let lhs = convert::calculate_total_copper_value(
+        multiplicand,
+        custom_currency_regex,
+        get_rates(currencies),
+    );
+
+    convert::exchange_currencies(lhs * multiplier, currencies, print_full).join(", ")
+}
+
+pub fn div_operation(
+    dividend: &str,
+    divisor: usize,
+    custom_currency_regex: &Regex,
+    currencies: &[Currency],
+    print_full: bool,
+) -> String {
+    let lhs = convert::calculate_total_copper_value(
+        dividend,
+        custom_currency_regex,
+        get_rates(currencies),
+    );
+
+    convert::exchange_currencies(lhs / divisor, currencies, print_full).join(", ")
+}
+
+pub fn copper_operation(
+    values: &str,
+    custom_currency_regex: &Regex,
+    currencies: &[Currency],
+) -> String {
+    let copper_value =
+        convert::calculate_total_copper_value(values, custom_currency_regex, get_rates(currencies));
+
+    format!("{}c", copper_value.separated_string())
+}
+
+pub fn default_operation(values: &str, currencies: &[Currency], print_full: bool) -> String {
+    let copper_value = convert::calculate_total_copper_value(
+        values,
+        &Regex::new(r"(0|(?:[1-9](?:\d+|\d{0,2}(?:,\d{3})*)))+([cegps])").unwrap(),
+        get_rates(config::phb_config().as_ref()),
+    );
+
+    let exchanged_currencies = convert::exchange_currencies(copper_value, currencies, print_full);
+
+    exchanged_currencies.join(", ")
+}
+
+fn get_rates(currencies: &[Currency]) -> HashMap<String, usize> {
+    currencies
+        .iter()
+        .map(|c| c.alias.clone())
+        .zip(currencies.iter().map(|c| c.rate))
+        .collect()
+}
+
+#[cfg(test)]
+mod test {
+    use std::collections::HashMap;
+
+    use currency::Currency;
+    use regex::Regex;
+
+    use super::{
+        add_operation, copper_operation, default_operation, div_operation, get_rates,
+        mul_operation, sub_operation,
+    };
+
+    lazy_static! {
+        static ref CURRENCIES: Vec<Currency> = vec![
+            Currency::new("penny", 1, "p", Some("pence".to_owned()), None),
+            Currency::new("shilling", 100, "s", Some("sterling".to_owned()), None),
+        ];
+        static ref CUSTOM_CURRENCY_REGEX: Regex = Regex::new(&format!(
+            "(\\d+)([{}])",
+            CURRENCIES
+                .iter()
+                .map(|c| c.alias.clone())
+                .fold(String::new(), |group, a| group + &a)
+        )).unwrap();
+    }
+
+    #[test]
+    fn test_get_rates() {
+        let rates: HashMap<_, _> = vec![("p".to_owned(), 1usize), ("s".to_owned(), 100usize)]
+            .into_iter()
+            .collect();
+        assert_eq!(rates, get_rates(&CURRENCIES));
+    }
+
+    #[test]
+    fn test_add_operation_same_currencies() {
+        let result = "3p".to_owned();
+        assert_eq!(
+            result,
+            add_operation("1p", "2p", &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_add_operation_diff_currencies() {
+        let result = "1s, 1p".to_owned();
+        assert_eq!(
+            result,
+            add_operation("1s", "1p", &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_sub_operation_smaller_subtrahend() {
+        let result = "1p".to_owned();
+        assert_eq!(
+            result,
+            sub_operation("2p", "1p", &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_sub_operation_larger_subtrahend() {
+        let result = "1p".to_owned();
+        assert_eq!(
+            result,
+            sub_operation("1p", "2p", &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_mul_operation() {
+        let result = "6p".to_owned();
+        assert_eq!(
+            result,
+            mul_operation("3p", 2, &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_div_operation_even_dividend() {
+        let result = "2p".to_owned();
+        assert_eq!(
+            result,
+            div_operation("4p", 2, &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_div_operation_odd_dividend() {
+        let result = "1p".to_owned();
+        assert_eq!(
+            result,
+            div_operation("3p", 2, &CUSTOM_CURRENCY_REGEX, &CURRENCIES, false)
+        );
+    }
+
+    #[test]
+    fn test_copper_operation() {
+        let result = "103c".to_owned();
+        assert_eq!(
+            result,
+            copper_operation("1s 3p", &CUSTOM_CURRENCY_REGEX, &CURRENCIES)
+        );
+    }
+
+    #[test]
+    fn test_default_operation() {
+        let result = "1 shilling";
+        assert_eq!(result, default_operation("1g", &CURRENCIES, true));
+    }
+
+    #[test]
+    fn test_default_operation_plural_output() {
+        let result = "2 sterling";
+        assert_eq!(result, default_operation("2g", &CURRENCIES, true));
+    }
+}

src/main.rs

@@ -1,120 +1,154 @@
 #[macro_use]
 extern crate clap;
-#[macro_use]
-extern crate lazy_static;
 extern crate regex;
+extern crate sterling_ops;
 
-use std::fmt;
-use std::ops::Add;
 use std::process;
 
 use regex::Regex;
+use sterling_ops::config;
+use sterling_ops::currency::Currency;
+use sterling_ops::*;
 
 fn main() {
-    lazy_static! {
-        static ref RE: Regex = Regex::new(r"(\d+)([cegps])?").unwrap();
-    }
-
     let app = clap_app!(sterling =>
-        (version: "0.1.0")
+        (version: env!("CARGO_PKG_VERSION"))
         (about: "Converts a given D&D 5e currency value to the Silver Standard.")
-        (@arg VALUE: ... "The value to be converted; should be suffixed with the coin's short-hand abbreviation, i.e. p, g, e, s, or c. Defaults coin type to 'g'.")
+        (@arg CONFIG: -c --config +takes_value "Specify location of config file; defaults to './sterling-conf.yml'.")
+        (@arg PRINT_FULL: -f --full "Print currencies with their full name, rather than with their alias")
+        (@arg OPTIONAL: -o --optional "Include currencies marked as optional when converting")
+        (@arg VALUE: ... "The value to be converted; should be suffixed with the coin's short-hand abbreviation, i.e. p, g, e, s, or c.")
+        (@subcommand add =>
+            (about: "Add two currency amounts together; uses the currencies defined in your config file")
+            (@arg AUGEND: +required "The augend of the addition function")
+            (@arg ADDEND: +required "The addend of the addition function")
+        )
+        (@subcommand sub =>
+            (about: "Subtract two currency amounts from one another; uses the currencies defined in your config file")
+            (@arg MINUEND: +required "The minuend of the subtraction function")
+            (@arg SUBTRAHEND: +required "The subtrahend of the subtraction function")
+        )
+        (@subcommand mul =>
+            (about: "Multiply a scalar multiplicand by a currency amount; uses the currencies defined in your config file")
+            (@arg MULTIPLIER: +required "The scalar multiplier of the multiplication function")
+            (@arg MULTIPLICAND: +required ... "The currency values to be multiplied")
+        )
+        (@subcommand div =>
+            (about: "Divide a currency amount by some scalar divisor; uses the currencies defined in your config file")
+            (@arg DIVISOR: +required "The scalar divisor of the division function")
+            (@arg DIVIDEND: +required ... "The currency values to be divided")
+        )
+        (@subcommand copper =>
+            (about: "Calculate the copper value of a custom currency")
+            (@arg VALUE: +required ... "The custom currency value")
+        )
     );
 
-    if let Some(values) = app.get_matches().values_of("VALUE") {
-        let coins: Vec<&str> = values.collect();
+    let matches = app.get_matches();
+    let config_result = config::load_config(match matches.value_of("CONFIG") {
+        Some(file) => file,
+        None => "./sterling-conf.yml",
+    });
 
-        let total_copper_value: usize = coins
+    let currencies: Vec<Currency> =
+        match config::parse_currency_config(config_result, matches.value_of("CONFIG")) {
+            Ok(currencies) => currencies
+                .into_iter()
+                .filter(|c| {
+                    let is_sub_command = match matches.subcommand_name() {
+                        Some(_) => true,
+                        None => false,
+                    };
+
+                    if is_sub_command {
+                        true
+                    } else {
+                        (!matches.is_present("OPTIONAL") && !c.is_optional())
+                            || matches.is_present("OPTIONAL")
+                    }
+                })
+                .collect(),
+            Err(error) => {
+                eprintln!("{}", error);
+                process::exit(1);
+            }
+        };
+
+    let custom_currency_regex: Regex = Regex::new(&format!(
+        "(\\d+)([{}])",
+        currencies
             .iter()
-            .map(|coin| {
-                if let Some(captures) = RE.captures(coin) {
-                    let amount: usize = captures.get(1).unwrap().as_str().parse().unwrap();
-                    let denomination = captures.get(2).map_or("g", |d| d.as_str());
-                    
-                    convert_to_copper(amount, denomination)
-                } else {
-                    panic!("Error: Invalid coin value \"{}\"", coin);
-                }
-            })
-            .fold(0 as usize, |total, value| total + value);
+            .map(|c| c.alias.clone())
+            .fold(String::new(), |group, a| group + &a)
+    )).unwrap();
 
-        println!("{}", exchange_copper(total_copper_value));
-    } else {
-        println!("Please enter at least one value; should be suffixed with the coin's short-hand abbreviation, i.e. p, g, e, s, or c. Defaults coin type to 'g'.");
-        process::exit(1);
-    }
-}
-
-fn convert_to_copper(amount: usize, coin_denomination: &str) -> usize {
-    match coin_denomination {
-        "p" => amount * 1000,
-        "g" => amount * 100,
-        "e" => amount * 50,
-        "s" => amount * 10,
-        "c" => amount,
-        _ => unreachable!("Invalid coin type; must be a valid coin found in the PHB."),
-    }
-}
-
-fn exchange_copper(copper: usize) -> CurrencyValue {
-    CurrencyValue {
-        platinum: copper / 1000000,
-        gold: (copper % 1000000) / 10000,
-        silver: ((copper % 1000000) % 10000) / 100,
-        copper: ((copper % 1000000) % 10000) % 100,
-    }
-}
-
-#[derive(Debug)]
-struct CurrencyValue {
-    platinum: usize,
-    gold: usize,
-    silver: usize,
-    copper: usize,
-}
-
-impl fmt::Display for CurrencyValue {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let &CurrencyValue {
-            platinum,
-            gold,
-            silver,
-            copper,
-        } = self;
-
-        let mut output = String::new();
-
-        if platinum > 0 {
-            output = output + &format!("{}p ", platinum);
+    let operation_result = match matches.subcommand() {
+        ("add", Some(command)) => add_operation(
+            command.value_of("AUGEND").unwrap(),
+            command.value_of("ADDEND").unwrap(),
+            &custom_currency_regex,
+            &currencies,
+            matches.is_present("PRINT_FULL"),
+        ),
+        ("sub", Some(command)) => sub_operation(
+            command.value_of("MINUEND").unwrap(),
+            command.value_of("SUBTRAHEND").unwrap(),
+            &custom_currency_regex,
+            &currencies,
+            matches.is_present("PRINT_FULL"),
+        ),
+        ("mul", Some(command)) => mul_operation(
+            &command
+                .values_of("MULTIPLICAND")
+                .unwrap()
+                .collect::<Vec<&str>>()
+                .join(" "),
+            command
+                .value_of("MULTIPLIER")
+                .unwrap()
+                .parse::<usize>()
+                .unwrap(),
+            &custom_currency_regex,
+            &currencies,
+            matches.is_present("PRINT_FULL"),
+        ),
+        ("div", Some(command)) => div_operation(
+            &command
+                .values_of("DIVIDEND")
+                .unwrap()
+                .collect::<Vec<&str>>()
+                .join(" "),
+            command
+                .value_of("DIVISOR")
+                .unwrap()
+                .parse::<usize>()
+                .unwrap(),
+            &custom_currency_regex,
+            &currencies,
+            matches.is_present("PRINT_FULL"),
+        ),
+        ("copper", Some(command)) => copper_operation(
+            &command
+                .values_of("VALUE")
+                .unwrap()
+                .collect::<Vec<&str>>()
+                .join(" "),
+            &custom_currency_regex,
+            &currencies,
+        ),
+        _ => {
+            if let Some(values) = matches.values_of("VALUE") {
+                default_operation(
+                    &values.collect::<Vec<&str>>().join(" "),
+                    &currencies,
+                    matches.is_present("PRINT_FULL"),
+                )
+            } else {
+                eprintln!("Sterling Error: please enter at least one value; should be suffixed with the coin's short-hand abbreviation, i.e. p, g, e, s, or c.");
+                process::exit(1);
+            }
         }
+    };
 
-        if gold > 0 {
-            output = output + &format!("{}g ", gold);
-        }
-
-        if silver > 0 {
-            output = output + &format!("{}s ", silver);
-        }
-
-        if copper > 0 {
-            output = output + &format!("{}c", copper);
-        } else if output.is_empty() {
-            output.push_str("0cp");
-        }
-
-        write!(f, "{}", output)
-    }
-}
-
-impl Add for CurrencyValue {
-    type Output = CurrencyValue;
-
-    fn add(self, other: CurrencyValue) -> CurrencyValue {
-        CurrencyValue {
-            platinum: self.platinum + other.platinum,
-            gold: self.gold + other.gold,
-            silver: self.silver + other.silver,
-            copper: self.copper + other.copper,
-        }
-    }
+    println!("{}", operation_result);
 }