Magma
Extending C with cmacro
Install / Use
/learn @eudoxia0/MagmaREADME
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Magma: cmacro_ extensions to C
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.. contents:: :local: :depth: 2
.. _cmacro: https://github.com/eudoxia0/cmacro
Overview
C is a tremendously useful language: It compiles everywhere, is generally fast, has a very long history and a stable standard, and comes with few bedrock abstractions.
Higher-level languages, like Common Lisp and Haskell, provide excellent metaprogramming systems and a very expressive type system, but have the cost of various bedrock abstractions like garbage collection, dynamic typing (In the case of Lisp), and exception handling.
cmacro provides a middleground: It bridges the power and control of C with the high-level metaprogramming systems of Lisp. This library uses cmacro to extend the capabilities of the C language.
Usage
Once you've built and installed_ cmacro, simply put these files in a directory
where they can be included by cmacro.
.. _built and installed: https://github.com/eudoxia0/cmacro#installing
Functions
Anonymous Functions
Syntax
:code:lambda (<args>*) -> <ret> { <body>* }
Description
Defines an anonymous function, returning a pointer to it.
Examples
.. code-block:: c
cmacro_import "fn/lambda.c"
int main() { int array[] = {423, 61, 957, 133, 969, 829, 821, 390, 704, 596};
qsort(array, 10, sizeof(int),
lambda (const void* a, const void* b) -> int
{ return *(int*)a - *(int*)b; });
for(size_t i = 0; i < 10; i++){
printf("%i ", array[i]);
}
return 0;
}
Lazy Evaluation
Syntax
- :code:
delay <expr> - :code:
force <expr>
Description
:code:delay takes an expression :code:expr and delays its computation until
the required time. :code:force takes this computation and executes it,
returning its value.
Examples
.. code-block:: c
force (delay 1) == 1;
Type System
Type-Inferenced Variables
Syntax
:code:var <name> = <value>
Description
Defines an implicitly-typed variable :code:var, giving it the value
:code:value. It is not possible to define a variable without an initial value.
Examples
.. code-block:: c
/* Input */ cmacro_import "type/var.c"
void f() { var a = 10; var b = 3.14; }
/* Output / void f() { typeof(10) a = 10; typeof(3.14) b = 3.14; / The above is, in fact, valid */ }
Algebraic Data Types
Syntax
Description
Examples
.. code-block:: c
#include <stdio.h>
cmacro_import "type/adt.c"
data Token { Integer { int i; }; String { char* str; }; }
int main() { Token a, b; construct(a, Token -> Integer) { 10 }; construct(b, Token -> String) { "test" }; switch(a.type) { case TokenInteger: return a.Integer.i; break; case TokenString: puts(b.String.str); break; } }
Tuples
Syntax
Description
Examples
.. code-block:: c
/* Input */ cmacro_import "type/tuple.c"
typedef tup(int, int) pair;
pair divrem(int n, int d) { return (pair){n/d, n%d}; }
/* Output */ typedef struct { int first; int second; } pair;
pair divrem(int n, int d) { return (pair){n/d, n%d}; }
Anaphoric Macros
Anaphoric macros store the output of an important argument (Like the condition
in the :code:if statement) in a variable named :code:it so they can be
accessed in the statement body.
:code:if
Syntax
- :code:
aif <cond> <true-branch> - :code:
aif <cond> <true-branch> else <false-branch>
Description
The value of :code:cond is stored in the variable :code:it, which is
accessible in the scope of either branch.
Examples
.. code-block:: c
/* Input */ cmacro_import "anaphoric/if.c"
int main() { aif(5 > 1) return it; }
/* Output */ int main() { typeof(5 > 1) it = 5 > 1; if(it) return it; }
Utilities
:code:doto
Syntax
:code:doto(obj) { <fn>(<args>*);+ }
Description
Calls every :code:fn, with :code:obj appended to the beginning of its
argument list.
Examples
.. code-block:: c
/* Input */ cmacro_import "util/doto.c"
void cancelAccount(Account* account) { doto(account) { setBalance(0); setStatus(DISABLED); } }
/* Output / void cancelAccount(Account account) { setBalance(account, 0); setStatus(account, DISABLED); }
:code:with_allocation
Syntax
- :code:
with_allocation(<ptr>, <type>) { <body>* } - :code:
with_allocation(<ptr>, <type>, <length>) { <body>* }
Description
Allocates memory to hold :code:type, optionally an array of :code:type if
:code:length is specified. The pointer is stored in the variable :code:ptr
and free'd after :code:body is executed.
Examples
.. code-block:: c
cmacro_import "util/with_allocation.c"
int main() { with_allocation(ptr, int, 10) { size_t i; for(i = 0; i < 10; i++) { ptr[i] = i*2; } } with_allocation(p, int) { *p = 10; return *p; } }
:code:with_open_file
Syntax
with_open_file(<stream>, <filepath>, <mode>) { <body>* }
Description
Opens :code:filepath with mode :code:mode, assigning it to the variable
:code:stream, then executes body and closes the stream.
Examples
.. code-block:: c
cmacro_import "util/with_open_file.c"
int main() { with_open_file(file, "README.md", "r") { printf("The first character in the README is: %c\n", fgetc(file)); } return 0; }
License
Copyright (c) 2014 Fernando Borretti (eudoxiahp@gmail.com)
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.
