#include <stdlib.h>
#include <stdio.h>

#define stack_define( TYPE )                                                 \
typedef struct _##TYPE##_stack_t {                                           \
        TYPE *array;                                                         \
        int array_size;                                                      \
        int array_capacity;                                                  \
} TYPE##_stack_t

#define stack_declare( TYPE )                                                \
TYPE##_stack_t

#define init( TYPE, initial_size )                                           \
{                                                                            \
        malloc( ( (initial_size >= 1) ? initial_size : 1 )*sizeof( TYPE ) ), \
        0,                                                                   \
        ( (initial_size >= 1) ? initial_size : 1 )                           \
}

#define free_stack( stack )                                                  \
free( stack.array )

#define pop( stack )                                                         \
if ( stack.array_size > 0 ) {                                                \
        --stack.array_size;                                                  \
}

#define push( TYPE, stack, element )                                         \
if ( stack.array_size < stack.array_capacity ) {                             \
        stack.array[stack.array_size] = element;                             \
        ++stack.array_size;                                                  \
} else {                                                                     \
        int i;                                                               \
        TYPE *tmp_array = stack.array;                                       \
                                                                             \
        stack.array = malloc( 2*(stack.array_capacity)*sizeof( TYPE ) );     \
                                                                             \
        for ( i = 0; i < stack.array_capacity; ++i ) {                       \
                stack.array[i] = tmp_array[i];                               \
        }                                                                    \
                                                                             \
        stack.array_capacity *= 2;                                           \
        free( tmp_array );                                                   \
                                                                             \
        stack.array[stack.array_size] = element;                             \
        ++stack.array_size;                                                  \
}

#define top( stack )                                                         \
( ( stack.array_size == 0 ) ? 0 : stack.array[stack.array_size - 1] )






stack_define( int );

int main(void) {
	stack_declare( int ) s = init( int, 10 );

	printf( "Pushing 3, 5, 7, and 9...\n" );
	push( int, s, 3 );
	push( int, s, 5 );
	push( int, s, 7 );
	push( int, s, 9 );

	printf( "Front:   %d\n", top( s ) );
	printf( "Popping twice...\n" );
	pop( s );
	pop( s );
	printf( "Front:   %d\n", top( s ) );
	printf( "Popping once...\n" );
	pop( s );
	printf( "Front:   %d\n", top( s ) );

	free_stack( s );

	return 0;
}