CSyntax.jl

C-like syntax for Julia
Author Gnimuc
Popularity
6 Stars
Updated Last
4 Months Ago
Started In
February 2019

CSyntax

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This package provides several macros for making life easier when translating C code to Julia.

Installation

pkg> add CSyntax

Submodules

CRef

This module provides a macro @cref/@c for emulating C's &(address) operator:

julia> using CSyntax.CRef

julia> function foo(x)
           x[] += 1
           return x
       end
foo (generic function with 1 method)

julia> x = 0
0

julia> @cref foo(&x)
Base.RefValue{Int64}(1)

julia> x
1

It's very useful when calling C-bindings from Julia. Comparing the following Julia code

vbo = GLuint(0)
@c glGenBuffers(1, &vbo)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), points, GL_STATIC_DRAW)

to

GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), points, GL_STATIC_DRAW);

they're nearly identical aside from the @c macro. Without this, one need to manually edit the code at least 3 more times and life will be quickly burning in the hell:

vboID = Ref{GLuint}(0)
glGenBuffers(1, vboID)
glBindBuffer(GL_ARRAY_BUFFER, vboID[])
# errors are waiting for you unless you dereference vboID correctly in every place hereafter

Note, everything after & will be treated as scalar except one dimensional arrays indexing in which case the corresponding pointer address will be retrieved, for example:

A = rand(10)
@c foo(a, b, &A[n]) # ==> foo(a, b, pointer(A) + n * Core.sizeof(eltype(A)))

but

A = rand(10)
@c foo(a, b, &A)
# this is not array indexing, so the result is
# A_cref = Ref(A)
# foo(a, b, A_cref)
# A = A_cref[]

CStatic

This submodule provides a @cstatic macro for emulating C's static syntax:

function foo()
    @cstatic i=0 begin
        for n = 1:10
            i += 1
        end
    end
end

vs

int foo(void) {
    static int i = 0;
    for (int n = 0; n < 10; n++) {
        i++;
    }
    return i;
}

@cstatic will return a tuple of current state of the input arguments, but note that jumping out from the @cstatic block (e.g. return, goto, etc.) is currently not supported, state changes before jumping will be lost.

CFor

This submodule provides a @cfor macro for emulating C's for-loops syntax:

julia> using CSyntax.CFor

julia> x = 0
0

julia> @cfor i=0 i<10 i+=1 begin
           global x += 1
       end

julia> x
10

# @cfor with @++
julia> using CSyntax: @++

julia> @cfor i=0 i<10 @++(i) begin
           i > 5 && continue  # well, this is actually illegal in C
           global x += 1
       end

julia> x
16

julia> let
           global j
           @cfor nothing (j > 3) j-=1 begin
               global x += 1
           end
       end

julia> x
23

CSwitch

This submodule provides C-like switch statement with the "falling through" behavior. It is inspired by dcjones's package Switch.jl which has died out since Julia v0.5. Anyway, it has been resurrected here.

julia> using CSyntax.CSwitch

julia> @enum test t=1 f=2

julia> tester = t
t::test = 1

julia> @cswitch tester begin
           @case t
               x = 1
               break
           @case f
               x = 2
               break
       end

julia> x
1

CEnum

CEnum.jl is also integrated in this package.

julia> @enum Foo a = 1 b = 2 c = 1
ERROR: LoadError: ArgumentError: values for Enum Foo are not unique
Stacktrace:
 [1] @enum(::LineNumberNode, ::Module, ::Any, ::Vararg{Any,N} where N) at ./Enums.jl:128
in expression starting at REPL[12]:1

julia> using CSyntax.CEnum

julia> @cenum(Bar, d = 1, e = 2, f = 1)

julia> d == f
true

TODO?

  • @cmacro? how to correctly handle recursive macro expansion rules?
  • @cdo-while? it's very trivial to implement but not very useful I guess
  • @cstar? * aka the so called indirection operator

Required Packages