Templates in C -- basically what you see in your nightmares

templates.py

#!/usr/bin/env python3
import sys

with open(sys.argv[1], 'r') as f:
    contents = f.read()
    contents += "\n\n"

i = 0
final_str = ""
while i < len(contents) - 1:

    if contents[i] == "%":
        i += 1
        if contents[i] == "^":
            template_string = ""
            i += 1
            while contents[i] != "\n":
                template_string += contents[i]
                i += 1
            old_i = i
            for j in template_string.split():
                i = old_i
                while contents[i] != "^" and contents[i + 1] != "%":
                    if contents[i] == "$" and contents[i + 1] != "$":
                        final_str += j
                    else:
                        final_str += contents[i]
                    i += 1
                
            i += 2
    
    final_str += contents[i]

    i += 1

with open(sys.argv[2], 'w') as f:
    autogenerated_message = "This file was automatically generated. Modify the file that generated this file instead, and rerun the python script."
    f.write(f"/// {'*' * len(autogenerated_message)} ///\n/// {autogenerated_message} /// \n/// {'*' * len(autogenerated_message)} ///\n\n" + final_str)

vector_gen.h

#pragma once

%^u32 i32 f32 f64
typedef union {
    struct {
        $ x;
        $ y;
    };
    $ data[2];
} V2$;
^%

vector_generated.h

/// ********************************************************************************************************************* ///
/// This file was automatically generated. Modify the file that generated this file instead, and rerun the python script. /// 
/// ********************************************************************************************************************* ///

#pragma once


typedef union {
    struct {
        u32 x;
        u32 y;
    };
    u32 data[2];
} V2u32;

typedef union {
    struct {
        i32 x;
        i32 y;
    };
    i32 data[2];
} V2i32;

typedef union {
    struct {
        f32 x;
        f32 y;
    };
    f32 data[2];
} V2f32;

typedef union {
    struct {
        f64 x;
        f64 y;
    };
    f64 data[2];
} V2f64;

Although it looks like the worst idea I've ever had, if it's polished up a bit and the templating features are improved, this could really be useful (for me at least).