#include <stdio.h>
#include <stdlib.h>
#include "memsim-decl.h"

int first(int lst){
	if(lst < MSIZE && lst != EMPTY){
		return(memory[lst]);
	}
	else{
		printf("Out of bounds\n");
		abort();
	}
}

int rest(int lst){
	if(lst <= MSIZE)
		return(memory[lst+1]);
	else
		printf("Out of bounds\n");
abort();
};

int cons(int first, int rest){
	int temp=0;

	if(next_mem >= MSIZE && free_list == EMPTY){
		printf("Cons out of memory fool\n");
		abort();
	}
	else{
		if(free_list == EMPTY){
			temp = next_mem;
			memory[next_mem] = first;
			memory[next_mem + 1] = rest;
			next_mem += 2;
		}
		else{
			temp = free_list;
			memory[free_list] = first;
			free_list = memory[free_list + 1];
			memory[temp + 1] = rest;
		}
	}
return(temp);
}

void give_back(int ptr){
	int p=ptr;
	while (memory[p+1] != EMPTY) {
		p = memory[p+1];
	}
	memory[p+1] = free_list;
	free_list = ptr;
}