From: Philip Mak <pmak@...>
Date: 2002-07-09T08:39:16+09:00
Subject: Should libraries perform type checking?

When coding a library that is meant to be reused in other code, is it
a good idea to make it so that the library will react gracefully if
you pass it a type that it wasn't expecting?

Ruby is a bit odd in that it has type restrictions to an extent, but
function definitions (i.e.  "def <name>(<args>)" do not include type
checking. Take this function for example:

    def CGI::escapeHTML(string)
        string.gsub(/&/n, '&amp;').gsub(/\"/n, '&quot;').gsub(/>/n, '&gt;').gsub(/</n, '&lt;')
    end

That is from cgi.rb. If you try to do this:

    CGI.escapeHTML(nil)

or pass it anything else that doesn't have a gsub() method, it will
crash but the error message it gives you is not meaningful and
requires actually looking at the code for cgi.rb to figure out what
happened.