⚠️ This is a work in progress so syntax and features or ideas may change in the future.
cgen-files are a form of template files to enable generics and other
metaprogramming things for C. Let's say we want to have a vector struct that has a specific number of fields depending on a number N.
The vectors field types are of type T. We also want to be able
to add two of these vectors with a function that is dynamically generated:
comments are not yet supported but I have them here for educational purposes
@comptime(T, N) // define comtpime constants
@alias(Vec = struct Vec_${N}D_${T}) // create alias that get resolved in identifiers
// create struct of name depending on the comptime constants
struct Vec_${N}D_${T} {
/*
dynamically create N fields
`..=` inclusive range from lhs to rhs, step size 1
`..<` exclusive range from lhs to rhs, step size 1
*/
@for (i : 1 ..= ${N}) {
${T} dim_${i};
}
};
// use of alias that gets resolved in return value and name of function
${Vec} vec_add_${N}d_${T}
(
${Vec} a, // another use of the alias
${Vec} b
) {
${Vec} result = {0};
// dynamically emit statements
@for (i : 1 ..= ${N}) {
result.dim_${i} = a.dim_${i} + b.dim_${i};
}
return result;
}Let's assume T=int and N=3. This would generate the following C code:
struct Vec_3_int
{
int dim_1;
int dim_2;
int dim_3;
};
struct Vec_3_int vec_add_3_int(struct Vec_3_int a, struct Vec_3_int b)
{
struct Vec_3_int result = {0};
result.dim_1 = a.dim_1 + b.dim_1;
result.dim_2 = a.dim_2 + b.dim_2;
result.dim_3 = a.dim_3 + b.dim_3;
return result;
}In the future I would like to read the comptime constants from a header file.
This allows the user to program with the interfaces given by the header file and the code generator will generate the C code for the user without needing to write the C code by hand for every possible combination of T and N they want to use. They just need to write the cgen file and the header file.