xor virgin no more

nkuitse on 2004-12-16T18:52:06

There's a rosy glow in my cheeks as I write this, for today I am an xor virgin no more.

That's right; I've just used Perl's xor operator for the first time, and it was a thrill!

The story of hoy

hoy (hack on yaml) is a script I wrote that lets me manipulate YAML documents from the command line. I can do things like create hashes and arrays:

$ hoy array 

$ echo -e "name Yolanda P. Ipswich\nage 3" | hoy hash
--- #YAML:1.0
age: 3
name: Yolanda P. Ipswich


Fetch values from a YAML hash:

$ hoy get -p name -i ulysses.yaml
Ulysses K. Fishwick


...and so on.  Each action is specified as a subcommand: hoy array ..., hoy foreach ..., etc.

hoy is very handy for what I do, and I love to say hoy.  (hoy! hoy! hoy!)

The deed itself

While making a few changes in hoy today, I realized that after reading options from the command line, subcommands that don't take any non-option arguments were ignoring extra, unused arguments.  That's not good, so I added a hash %takes_arguments:

my %takes_arguments = (
    'foreach' => 1,
);


Then I added some code right after a call to GetOptions(...) that checks for argument "overflow":

exit usage()
    if $takes_arguments{$cmd} and not scalar(@ARGV);


Then I realized I might as well check for argument "underflow" at the same time, and that's when it happened: the xor revelation (*blush*):

exit usage()
    if $takes_arguments{$cmd} xor scalar(@ARGV);


Postscript

It took me a while to realize I should use xor; I first changed it to this:

exit usage()
    if ($takes_arguments{$cmd} != 0) eq (scalar(@ARGV) != 0);


Only then did I realize I was on the cusp of something new and amazing.  And now, things will never be the same...