KC3 v0.1.14

KC3 is a programming language with meta-programmation and a graph database embedded into the language. It aims to be the language for semantic programming, and programming the semantic web.

This is a development branch, see KC3 v0.1.13 for a stable release.

KC3 is currently a programming language project, inspired by C, Elixir and Common Lisp. It could be described as C with Elixir modules, pattern matching, and a semantic object system. The idea is to plug modules, closures, pattern matching, a graph database and metaprogramming into C99 with an extremely small set of dependencies.

Supported operating systems (additional dependencies) :

• BSD
• Linux (libbsd, libmd)
• MacOS X (libmd)
• Windows (MSys2)

Supported architectures :

• aarch64 (arm64, Apple M1, Apple M2)
• amd64
• i386
• sparc64

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Join us on kmx.io Discord server !

Usage

Install dependencies

Debian / Ubuntu / PopOS

# install build tools
sudo apt install pkg-config clang libtool-bin make ruby time

# install dependencies
sudo apt install libffi-dev libbsd-dev libevent-dev

# use clang
export CC=clang

# update symlinks
cd lib/kc3/0.1 && ln -sf ../../../ekc3/.libs/libekc3.so ekc3.so

Compilation

git clone https://git.kmx.io/kc3-lang/kc3.git
cd kc3
git submodule init
git submodule update
cd fonts
git submodule init
git submodule update
cd ..
./configure
make

Add the sources to LD_LIBRARY_PATH

export LD_LIBRARY_PATH=$PWD/libkc3/.libs:$PWD/ekc3/.libs:$PWD/lib/kc3/0.1

Running the OpenGL demo

make demo_gl

Press Q to quit, F for fullscreen, Left and Right arrows to move through sequences.

Other targets exist :

make demo_gl_asan
make gdb_demo_gl
make lldb_demo_gl

Running the Cairo demo

make demo

Press Q to quit, Left and Right arrows to move through sequences.

Other targets exist :

make demo_asan
make gdb_demo
make lldb_demo

Running the HTTPd demo

make test_httpd

Running the tests

make test

All the tests will be run. More specific targets exist :

make test_libkc3
make test_ikc3
make test_libkc3_asan
make test_ikc3_asan
make test_asan

Running ikc3

ikc3/.libs/ikc3

Running gdb

make gdb_ikc3
make gdb_test

Adding or removing files from the source tree

make gen
./update_sources

Don’t forget to commit your files and the modified sources.mk and sources.sh files.

Structure

libkc3

KC3 is implemented using libkc3 a small C99 library implementing the core of the language.

The library includes a parser and an interpreter for KC3 code in C structures.

Support for large integers provided by libtommath.

Support for C function calls provided by libffi.

Modules are saved as facts databases.

Parser

The parser is recursive descent.

AST

The AST is represented as KC3 data structures and can be meta-programmed in C.

Interpreter

Under development.

ikc3

Interactive shell. Terminal I/O provided by linenoise.

Example :

$ make test
$ ikc3/ikc3
ikc3> ikc3> 1 + 1
2
ikc3> 2 + 2
4
ikc3> 3 + 3
6
ikc3> 1 +
ikc3> 1
2
ikc3> double = fn (x) { x * 2 }
fn (x) { x * 2 }
ikc3> double
fn (x) { x * 2 }
ikc3> double(1)
2
ikc3> double(2)
4
ikc3> double(3)
6
ikc3> double(4)
8
ikc3> List.map([1, 2, 3, 4], double)
[2, 4, 6, 8]
ikc3> List.reverse(List.map([1, 2, 3, 4], double))
[8, 6, 4, 2]

The List.map and List.reverse functions are defined in lib/kc3/0.1/list.kc3 and can be modified in real time.

For example, without closing ikc3 let’s redefine List.reverse, open an editor and change the line in lib/kc3/0.1/list.kc3 from

  def reverse = fn {
    (x) { reverse(x, ()) }
    ([], acc) { acc }
    ([a | b], acc) { reverse(b, [a | acc]) }
  }

to

  def reverse = fn {
    (x) { reverse(x, ()) }
    ([], acc) { [:reversed | acc] }
    ([a | b], acc) { reverse(b, [a | acc]) }
  }
}}

and check the results of the last command (up key) in ikc3/ikc3 :

ikc3> List.reverse(List.map([1, 2, 3, 4], double))
[:reversed, 8, 6, 4, 2]

Don’t forget to revert the changes to list.kc3.

Maps

KC3 maps are key-value stores, you can use any tag as a key and associate a value to it.

You can use destructuring to access KC3 maps :

ikc3> a = %{id: 1, title: "My title", message: "Hello, world !"}
%{id: 1, title: "My title", message: "Hello, world !"}
ikc3> a = %{}
%{id: 1, title: "My title", message: "Hello, world !"}
ikc3> %{id: id, title: "My title", message: message} = a
%{id: 1, title: "My title", message: "Hello, world !"}
ikc3> id
1
ikc3> message
"Hello, world !"

You can use the dot syntax to access map values from a Sym key :

ikc3> a = %{id: 1, title: "My title", message: "Hello, world !"}
%{id: 1, title: "My title", message: "Hello, world !"}
ikc3> a.id
1
ikc3> a.message
"Hello, world !"

You can also use the KC3.access function for the same result :

ikc3> a = %{id: 1, title: "My title", message: "Hello, world !"}
%{id: 1, title: "My title", message: "Hello, world !"}
ikc3> access(a, :id)
1
ikc3> access(a, :message)
"Hello, world !"

Unicode characters

ikc3 fully supports Unicode :

Some unicode characters :

ikc3> '\U+1B2FB'
'𛋻'
ikc3> '𐅀'
'𐅀'
ikc3> '🤩'
'🤩'
ikc3>

Large integers

ikc3> a = 1 + 100000000000000000000000000000000
100000000000000000000000000000001
ikc3> a * a
10000000000000000000000000000000200000000000000000000000000000001
ikc3>

Ratios

Ratios are made with a couple of large integers : the numerator which can be any number, and the denominator which has to be positive. They represent fractions of integral numbers. They are written with a slash and no space.

ikc3> 1/2 + 2/3
7/6
ikc3> 1/2 * 2/3
1/3
ikc3> 1/2 / 2/3
3/4
ikc3> 1/2 - 2/3
-1/6

Complex numbers

Complex numbers are constructed using the operator +i on any kind of numbers (unsigned, signed, float, ratios, and even other complex numbers). For instance, you can write a +i b where a and b are real numbers.

ikc3> 1 +i 2
1 +i 2
ikc3> 1 +i 2 + 2 +i 3
3 +i 5
ikc3> (1 +i 2) * (2 +i 3)
-4 +i 7
ikc3> (1 +i 2) / (2 +i 3)
0 +i 0
ikc3> (1/1 +i 2/1) / (2 +i 3)
8/13 +i 1/13

As you can see integer division is not producing ratios. That might change in future releases.

Lists

Lists are marked with brackets [].

Regular lists can be :

• an element and a list : [1 | []] → [1]
• multiple elements : [1, 2, 3]
• multiple elements and a list : [1, 2 | [3, 4]] → [1, 2, 3, 4]
• the empty list : []

Regular lists end with the empty list : [1] == [1 | []].

You can also contruct dotted lists like in Common Lisp where the next list pointer is an arbitrary form. E.g. :

• an element and an element : [1 | 2]
• multiple elements and an element : [1, 2, 3 | 4]
• the empty list and an element : [[] | 1]

All these list formats are supported in pattern matching.

Pattern matching and destructuring

The KC3 pattern matching principles come from Erlang and Elixir.

All tag data structures in KC3 can be pattern matched using the equal sign (=) against litteral values containing identifiers. All identifiers are supposed to be new bindings when using pattern matching in KC3. If you want to use an identifier’s value in pattern matching you must use the pin operator (^). Variables can be assigned a new value from either side of the equal sign and from inside a tag data structure, which is called destructuring.

Examples :

ikc3> a = 1
1
ikc3> a = 2
2
ikc3> a
2
ikc3> ^ a = 1
void
ikc3> ^ a = 2
2
ikc3> ^ a = b
2
ikc3> b
2

To use destructuring just type the litteral value you want to match and put identifiers (variable names) where you want a variable matching the value on the other side of the equal sign. This is the most visual approach possible to text-based value matching : the data is constantly matched to litterals that show their type to the programmer. This is really helpful when writing large programs that need to scale in the way of abstractions. Let the data flow in the code through visual types.

Examples :

ikc3> [x, y | z] = List.reverse([1, 2, 3, 4])
[4, 3, 2, 1]
ikc3> x
4
ikc3> y
3
ikc3> z
[2, 1]

Macros

KC3 macros are like Common Lisp macros with Elixir pattern-matching.

Macros are like functions but start with macro instead of fn and their arguments do not get evaluated. However they get pattern matched and the full power of the pattern matcher is available for arguments destructuring. Use a map if you want named arguments. Use a list if you want &rest arguments, use a block if you want a &body argument.

When evaluated, a macro call returns a tag which is in turn evaluated in the calling site lexical environment. This allows for DSLs and custom control structures to be defined in KC3.

Many basic operations in KC3 are defined as macros : error handling, free operations with unwind-protect, graph database operations like Facts.with.

If, then, else.

Conditionals in KC3 are like in Ruby, for example :

ikc3> if true && true
ikc3>   1 + 1
ikc3>   2 + 2
ikc3> end
4

ikc3> if true && false
ikc3>   1 + 1
ikc3>   2 + 2
ikc3> else
ikc3>   3 + 3
ikc3>   4 + 4
ikc3> end
8

A KC3 if statement always return a value. If the condition is true, the first (then) block gets evaluated. If the condition is false the second block gets evaluated. If the condition is false and an else block is not provided, then void gets returned.

One liner examples with then :

ikc3> if 42 then 100 else 101 end
100
ikc3> if 0 then 100 else 101 end
101

defmodule and def

Example :

ikc3> defmodule Example do
ikc3>   def three = 3
ikc3>   def double = fn (x) do x * 2 end
ikc3>   def double_tuple = macro (x) do {x, x} end
ikc3>   def operator_double = %KC3.Operator{sym: :double, symbol_value: fn (x) { x * 2 }
ikc3> end
Example
ikc3> Example.three
3
ikc3> Example.double
fn (x) do x * 2 end
ikc3> Example.double(21)
42
ikc3> Example.double_tuple(:ok)
{:ok, :ok}
ikc3> double 21
42

Facts

The Facts module allows read and write access to a graph database containing facts : triples of subject, predicate, object.

Examples for querying the KC3 database containing all definitions of the interpreter :

ikc3> Facts.with_tags(Facts.env_facts(), KC3, :operator, ?,
        fn (fact) { puts(fact.object); :ok })
operator_eq
operator_gt
operator_lt
[...]
:ok

kc3s

Script interpreter. Works the same as ikc3 but is not interactive and does not output results.

HTTPd

HTTP daemon, use make test_httpd.

The http daemon is defined in httpd/httpd.c and lib/kc3/0.1/httpd.kc3.

The http daemon is a static file server listing directories and serving files for display or download (Web 1.0).

TODO

• HTTPd v0.2.0

  • dynamic pages (MVC)
    • [DONE] controllers
      • [DONE] ./app/controllers/
    • [DONE] templates
      • [DONE] ./app/templates/
    • dynamic router
      • [DONE] Str.starts_with?(url, route.path)
      • HTTPd.Router.get(“/user/:id/articles/*slug/edit”, UserArticlesController.show)
    • views
      • ./app/views/

• libkc3

  • evaluation order for && and ||
  • operators dispatch
    • list of matching operators (facts_with)
  • base-specific big floats
  • macro cast (Macro) fn (x) { x }
  • pretty printer
    • [DONE] indent
    • 80 columns (\n)
  • tags
    • walker
    • height function (TAG_VOID: 1, TAG_TUPLE: (1+ (max (height tuple->tags))))
    • has_ident
    • collect_idents
  • facts
    • negative facts : 4 + 2n = not 3 + 2n
    • with ignore variables
  • math
    • arbitrary precision floating point numbers (decimals)
  • map
    • get (get key value)
    • put (return a new map)
  • struct
    • access
    • get
    • put
  • enums
  • unions
  • errors (setjmp, longjmp)
    • stacktrace
      • ffi ?
        • libdwarf
  • control structures
    • when
    • unless
    • switch/case/cond
  • unwind protect
  • functions
    • return
  • livebook
    • gaussian
  • buf_sha256
  • buf_popen
  • tests

License

KC3

/* kc3
 * Copyright 2022,2023,2024 kmx.io <contact@kmx.io>
 *
 * Permission is hereby granted to use this software granted the above
 * copyright notice and this permission paragraph are included in all
 * copies and substantial portions of this software.
 *
 * THIS SOFTWARE IS PROVIDED "AS-IS" WITHOUT ANY GUARANTEE OF
 * PURPOSE AND PERFORMANCE. IN NO EVENT WHATSOEVER SHALL THE
 * AUTHOR BE CONSIDERED LIABLE FOR THE USE AND PERFORMANCE OF
 * THIS SOFTWARE.
 */

Linenoise

Copyright (c) 2010-2014, Salvatore Sanfilippo <antirez at gmail dot com>
Copyright (c) 2010-2013, Pieter Noordhuis <pcnoordhuis at gmail dot com>

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modification, are permitted provided that the following conditions are met:

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  this list of conditions and the following disclaimer in the documentation
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Unicode Character Database

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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 <https://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 https://www.gnu.org/licenses/.

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 https://www.gnu.org/licenses/why-not-lgpl.html.

Others

See the LICENSE file in subdirectories.