commit ac9719ad57af37ad7f4a62dde8b864faad0d4e04
Author: Peter J. Holzer <hjp@hjp.at>
Date:   Wed Sep 26 16:17:39 2012 +0200

    Initial version

diff --git a/rpn b/rpn
new file mode 100755
index 0000000..70606be
--- /dev/null
+++ b/rpn
@@ -0,0 +1,53 @@
+#!/usr/bin/perl
+use warnings;
+use strict;
+use Term::ANSIColor;
+use Math::Trig ':pi';
+
+my @stack;
+my $input_color = 'red';
+my $stack_color = 'blue';
+print color $input_color;
+while (<>) {
+    for (split) {
+	if (m{^[-+*/]|\*\*$}) {
+	    my $y = pop @stack;
+	    my $x = pop @stack;
+	    my $z = eval "$x $_ $y";
+	    push @stack, $z;
+	} elsif (m{^sqrt$}) {
+	    my $x = pop @stack;
+	    my $z = eval "$_($x)";
+	    push @stack, $z;
+	} elsif (m{^pi$}) {
+	    push @stack, pi;
+	} elsif (m{^swap$}) {
+	    my $y = pop @stack;
+	    my $x = pop @stack;
+	    push @stack, $y;
+	    push @stack, $x;
+	} elsif (m{^pop$}) {
+	    pop @stack;
+	} elsif (m{^dup$}) {
+	    my $x = pop @stack;
+	    push @stack, $x;
+	    push @stack, $x;
+	} elsif (m{^log$}) {
+	    my $x = pop @stack;
+	    push @stack, log($x) / log(10);
+	} elsif (m{^ln$}) {
+	    my $x = pop @stack;
+	    push @stack, log($x);
+	} elsif (m{^ld$}) {
+	    my $x = pop @stack;
+	    push @stack, log($x) / log(2);
+	} else {
+	    push @stack, $_;
+	}
+    }
+    for (@stack) {
+	print color $stack_color;
+	print "$_\n";
+    }
+    print color $input_color;
+}