# rpn.pl^
#						RPN CALC  of Perl
#																by guel 
#																09/22/95
#																05/06/96
#																07/15/97

print "RPN CALC of Perl, ready. \t created by guel\n";

while (<>) {
    chop;

    foreach (split) {
		if (&isNum($_))	{ &Push($_) }
		elsif ($_ eq '+') { $lastX = &Pop(); &Push(&Pop() + $lastX) }
		elsif ($_ eq '-') { $lastX = &Pop(); &Push(&Pop() - $lastX) }
		elsif ($_ eq '*') { $lastX = &Pop(); &Push(&Pop() * $lastX) }
		elsif ($_ eq '/') { $lastX = &Pop(); &Push(&Pop() / $lastX) }

		elsif (/^(\+\-|[lL])$/)	{ $lastX = &Pop(); &Push(   - $lastX) }
		elsif (/^(1\/x|[xX])$/)	{ $lastX = &Pop(); &Push( 1 / $lastX) }
		elsif (/^(sqrt|[zZ])$/)	{ $lastX = &Pop(); &Push(sqrt($lastX)) }
		elsif (/^(last|[bB])$/)	{ &Push($lastX) }
		elsif (/^(down|[vV])$/)	{ &Pop() }						# ��
		elsif (/^(xy|[cC])$/)	{
			a = &Pop(); b = &Pop(); &Push(a); &Push(b) }		# x<=>y
	}

    printf "%g\n", $stack[$#stack];
	print join(" ",@stack);
    printf "\t (LastX=%g) (stack_depth=%d)\n", $lastX, $#stack;
}


sub Push {
	push(stack, $_[0]);
}

sub Pop {
	if ($#stack > -1) {
		return pop(stack);
	} else {
		printf "error: poped empty stack\n";
    }
}


sub isNum {
	/^[+\-]?(\d+|\d*[.]\d+)(|[eE][+\-]\d+)$/
}