#include "mydefs1.h"
#include <assert.h>

// Array implementation of stacks. 
// Grow from high index towards 0.

void Istack :: init(int nitems = 100)
{
        sz = nitems;
        stack = new int[sz];
        top = sz;
}
void Istack :: push(int x)
{
        assert( !isfull() );
        stack[--top] = x;
}
int Istack :: pop()
{
        assert( !isempty() );
        return( stack[top++] );
}
bool Istack :: isempty()
{
        return( top == sz );
}
bool Istack :: isfull()
{
        return( top == 0 );
}