#include <stdio.h>
#include "stack.h"

static int sp=0;
element val[STACKSIZE];

void push(element x) {
    if (sp < STACKSIZE)
	val[sp++] = x;
    else
	fprintf(stderr, "ERROR. push: stack full, can't push %g\n", x);
}

element pop(void) {
    if (sp > 0)
	return val[--sp];
    else {
	fprintf(stderr, "ERROR. pop: stack is empty.\n");
	return 0.;
    }
}

element dup(void) {
    if (sp > 0)
	return val[sp-1];
    else {
	fprintf(stderr, "ERROR. pop: stack is empty.\n");
	return 0.;
    }
}

void down(void) {
    int i;
    element z;
    z = val[0];
    for (i=0; i<sp; ++i)
	val[i] = val[i+1];
    val[sp-1] = z;
}

void up(void) {
    int i;
    element z;
    z = val[sp-1];
    for (i=sp-1; i>0; --i)
	val[i] = val[i-1];
    val[0] = z;
}

void list(void) {
    int i;
    for (i=sp-1; i>=0; --i)
	printf("\t%.8g\n", val[i]);
}

void swaptop(void) {
    element z;
    if (sp > 1) {
	z = val[sp-1];
	val[sp-1] = val[sp-2];
	val[sp-2] = z;
    }
    else
	fprintf(stderr, "ERROR. swaptop: not enough in stack.\n");
}

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