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/*
* Stack implemented using linked list.
* This is free and unencumbered software released into the public domain.
*/
#include <stdlib.h>
#include "stack.h"
stack *mkstack()
{
stack *s = malloc(sizeof(stack));
s->stack = NULL;
return s;
}
int stack_empty(stack *s)
{
return s->stack == NULL;
}
void stack_push(stack *s, void *item)
{
s->stack = cons(item, s->stack);
}
void *stack_top(stack *s)
{
return car(s->stack);
}
void *stack_pop(stack *s)
{
void *first = car(s->stack);
construct *rest = cdr(s->stack);
free(s->stack);
s->stack = rest;
return first;
}
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