dabeaz_stb.c

#include <stdio.h>
#include <stdarg.h>

// https://github.com/nothings/stb
#define STB_DS_IMPLEMENTATION
#include "stb_ds.h"

// compile with: gcc -Wall -I . dabeaz_stb.c -o a && ./a

typedef struct datum datum;

typedef enum valtype {
    INT,
    STR,
    LIST
} valtype;

typedef union val {
    int integer;
    char* string;
    datum** child;
} val;

struct datum {
    valtype type;
    val value;
};

void print_list(datum** data) {
    printf("[");
    for (int i=0; i < arrlen(data); i++) {
        switch(data[i]->type) {
            case INT:
                printf(" %d ", data[i]->value.integer);
                break;
            case STR:
                printf(" %s ", data[i]->value.string);
                break;
            case LIST:
                print_list(data[i]->value.child);
                break;
        }
    }
    printf("]");
}

datum* int_(int i) {
    datum* d = malloc(sizeof(datum*));
    d->type = INT;
    d->value = (val) { .integer = i };
    return d;
}

datum* str(char* str) {
    datum* d = malloc(sizeof(datum*));
    d->type = STR;
    d->value = (val) { .string = str };
    return d;
}

datum* list(int n, ...) {
    datum** lst = NULL;
    va_list values;
    va_start(values, n);
    for (int i=0; i < n; i++) {
        arrput(lst, va_arg(values, datum*));
    }

    datum* d = malloc(sizeof(datum*));
    d->type = LIST;
    d->value = (val) { .child = lst };
    return d;
}

int main() {
    datum* data =
        list(3,
            str("+"), 
            list(3, str("*"), int_(1), int_(2)),
            list(4, str("*"), int_(3),
                    list(3, str("+"), int_(4), int_(5)),
                    str("x")
            ));

    print_list(data->value.child);
    printf("\n");

    return 0;
}