#!/usr/bin/perl
# Copyright (c) 2003-2009 David Caldwell -*- cperl -*-

use strict;
use warnings;

sub revstr($) { join "", reverse split //, $_[0] } # Reverse the characters in a string.
sub comma($$) { revstr join(",", unpack("(A$_[1])*", revstr($_[0]))) }

sub compute ($) {
    $_[0] =~ s/\b([\d.]+)([kmgtpezyKMGTPEZY])[bB]?/($1*1024**(index("kmgtpezy",lc "$2")+1))/g;
    my $a = eval($_[0]); die unless defined $a;
    my $i = eval("use bigint; $_[0];"); $i = $a unless defined $i;
    my $n = eval("use bignum; $_[0];"); $n = $a unless defined $n;
    my $r = eval("use bigrat; $_[0];"); $r = $a unless defined $r;
    my $is = "";
    eval { $is = $i->copy()->bfloor().""; };
    $is = int $i if $@;
    my $hs = eval { $i->as_hex; } || sprintf "%#x", $i;
    my $ic = comma($is,3);
    my $hc = "0x". comma(($hs =~ /0x(.*)/)[0], 4);
    print "$ic";
    print " $is" if $ic ne $is;
    print " $hc";
    print " $hs" if $hc ne $hs;
    printf " %#o", $a;
    if ($n > 1024) {
        use POSIX;
        use List::Util 'min';
        my @pow2 = qw(B KB MB GB TB PB EB ZB YB);
        # This is weird because we can't use a bigint directly since log(bigint(1<<400))
        # takes hours (literally). So we convert into a perl scalar so we can use fast
        # floating point log() (the precision we lose going to a scalar doesn't matter
        # in the context of log()) and then convert back to a bigint for the pow().
        my $exp = Math::BigFloat->new(min($#pow2, POSIX::floor(log($n->numify)/log(1024))));
        my $coeff = $n / (1024 ** $exp);
        if ($coeff >= 100000) {
            printf " %6.2e%s", $coeff, $pow2[$exp];
        } elsif ($coeff->copy->bfloor() * 1024 ** $exp == $n) {
            print " $coeff",$pow2[$exp];
        } else {
            printf " %.2f%s", $coeff, $pow2[$exp];
        }
    }
    printf " %.15s",$n if $is ne $n."";
    print  " $r"       if $is ne $r."" && $n."" ne $r."";
    printf " '%c'",$a  if $a >= ord ' ' && $a <= ord '~';
    printf " %b", $i   if $i < 0x10000;
    print  "\n";
}

if ($#ARGV != -1) {
    compute $_ foreach (@ARGV);
} else {
    if (eval "use Term::ReadLine;1;") {
        my $term = new Term::ReadLine 'Perl Calc';
        while (defined ($_ = $term->readline('pc] '))) {
            next unless /\S/;
            eval { compute($_) };
            print "$@" if $@;
            $term->addhistory($_);
        }
        print "\n";
    } else {
        while (<>) {
            compute($_);
        }
    }
}

__END__

=head1 NAME

PC - A simple but feature filled command line Perl calculator

=head1 SYNOPSIS

  pc 11+3

=head1 DESCRIPTION

C<pc> is a quick and dirty command line perl calculator. Pass it an
expression on the command line and it will print the result in a number of
different formats. You can also run C<pc> with no command line parameters
and it will run an interactive loop (using C<L<Term::ReadLine>> if you have it
installed).

C<pc> is designed to give you all the output you ever could want without
having to memorize any stupid command line switches. There are none, in
fact. It also doesn't overload you with redundant data. If the floating
point answer is the same as the integer answer then it doesn't show it to
you. Same with the fractions.

=head1 TUTORIAL

=head2 The basics

  $ pc 11+3
  14 0xe 016

The first number is the integer result, followed by the hex and octal
representations. Simple enough.

=head2 Order of operations

This shows that C<pc> uses Perl's order of operations (operator precedence if
you are in a programming mood):

  $ pc 1+3*2
  7 0x7 07

=head2 ASCII

  $ pc 1+3*20
  61 0x3d 075 '='

Here we see an extra field was printed. In this case C<pc> detected the final
integer value was in the ASCII range and printed the character represented
by the value 61, an equal sign.

=head2 Bitwise Operations

We also get Perl (and C) style bitwise operators:

  $ pc '1+3*20<<2 & 0xff'
  244 0xf4 0364

Also notice that I had to quote it since (a) I put a space in the
expression and (b) I used the '<' and '&' characters which mean something to
the shell.

=head2 Floating point

Of course it's not restricted to only integers, it can handle floats too:

  $ pc 1+3*20/55
  2 0x2 02 2.0909090909090 23/11

You'll notice it shows the result of the floating point math in addition to
the integer math.

=head2 Fractions

You might have noticed a fraction in the output of the previous example. C<pc>
uses Perl's "bigrat" library to do fractions:

  $ pc 3/4+1/2
  0 0x0 01 1.25 5/4

=head2 Human readable

  $ pc 1000*2000
  2,000,000 2000000 0x1e,8480 0x1e8480 07502200 1.90MB

You'll notice that the integer and hex results are printed twice--one with
commas and one without. The one with commas is so that you the human can
read the output easily. The one without commas is for copying and
pasting. You should also notice that C<pc> helpfully told you the number was
1.90MB. If a number is bigger than 1024 (1KB) it will print it in human
readable byte quantity.

=head2 Power of 2 magnitude suffixes

It also accepts magnitude suffixes on the input:

  $ pc 16m
  16,777,216 16777216 0x100,0000 0x1000000 0100000000 16MB

The following suffixes are allowed: kmgtpezy (lower or upper case, with or
without a trailing "b"). Note that the human readable output "16MB" doesn't
have a decimal point. It will remove the decimal point if the number is
exactly that value. So:

  $ pc 16m+1
  16,777,217 16777217 0x100,0001 0x1000001 0100000001 16.0MB

Since "16.0MB" has a decimal point, we know the value isn't exactly 16
megabytes.

=head2 Large numbers

C<pc> uses Perl's bigint so that it can handle numbers bigger than 32 bits:

  $ pc '1<<40'
  1,099,511,627,776 1099511627776 0x100,0000,0000 0x10000000000 020000000000000 1TB

=head2 Trancendental and trignomentric functions

C<pc> gives you access to all the Perl math functions:

  $ pc 'sin(3.141592) ** .5'
  1 0x1 0 0.0008084490047 1.772453666531229808666207156690905830337 1

=head2 Random Perl code

  $ pc 'ord("a")'
  0x61 0141 97 'a'

Since C<pc> uses Perl's eval you can do arbitrary perl code too. Though frankly
the only thing I've ever used is ord().

=head1 SEE ALSO

L<http://porkrind.org/missives/pc-perl-calculator>

=head1 COPYRIGHT

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

Copyright (C) 2003-2009 David Caldwell

=head1 AUTHOR

David Caldwell <david@porkrind.org>

=cut