options.c

#include <stdint.h>
#include <stdio.h>
#define ENONE -999
typedef int Err;

// TODO: this isn't so much an optional type as it is a Result type, like in Rust. rename accordingly (e.g. Result->Value/Type;
//       Option->Result)
typedef union {
    int8_t    i8;
    int16_t  i16;
    int32_t  i32;
    int64_t  i64;

    uint8_t   u8;
    uint16_t u16;
    uint32_t u32;
    uint64_t u64;

    float      f;
    
    void*      v;
} Result;

typedef struct {
    Result result;
    Err error;
} Option;

int has_value(Option* o) {
    return o->error == ENONE;
}
Err get_err_code(Option* o) {
    return o->error;
}
Result get_result(Option* o) {
    return o->result;
}

/**
 * \brief foobar
 * \return An Option<int32_t> containing result or error
 */
Option foo() {
    int i = 10;
    Option o = {
        .result = { .i32 = i },
        .error  = ENONE,
    };
    return o;
}

Option bar() {
    Option o = {
        .error = 69, // set to some meaningful, well-documented value
    };
    return o;
}

int main() {
    Option o = foo();
    printf("has value: %d\n", has_value(&o));
    if (has_value(&o)) {
        printf("result = %d\n", get_result(&o).i32);
    } else {
        printf("error occurred! %d\n", get_err_code(&o));
    }
    o = bar(); // reuse name
    if (has_value(&o)) {
        printf("result = %s\n", get_result(&o).str);
    } else {
        printf("error occurred! %d\n", get_err_code(&o));
    }
}