// closure.c
// Example to show how lambda functions can be implemented using C code.

#include <stdio.h>

typedef int (*fp_t)(); // function pointer
typedef struct { int x; } G_ENV;
typedef struct { fp_t lambda; G_ENV env; } G_CLOSURE;

int g_lifted_lambda(G_ENV g_env) { return g_env.x; }

G_CLOSURE f_create_closure(int x) {
  G_ENV g_env;  g_env.x = x;
  G_CLOSURE clsr; clsr.env = g_env;  clsr.lambda = g_lifted_lambda;
  return clsr;
}

int main() {
    G_CLOSURE a, b;

    // a = f(10) in Python becomes . . .
    a = f_create_closure(10);
    
    // b = f(20) in Python becomes . . .
    b = f_create_closure(20);

    // a() in Python becomes . . .
    printf("Output of evaluating a() = %d\n", a.lambda ( a.env ));

    // b() in Python becomes . . .
    printf("Output of evaluating b() = %d\n", b.lambda ( b.env ));

    return 1;
}