Ruby

There should be Regexp#to_regexp, just as there is Array#to_ary and String#to_str.

p [].to_ary # => [] p ''.to_str # => "" p //.to_regexp # undefined method `to_regexp`... 

The use case is code like this:

if o.respond_to?(:to_ary) # do something with o.to_ary elsif o.respond_to?(:to_str) # do something with o.to_str elsif o.respond_to?(to_regexp) # can't do this today # do something with o.to_regexp 

The workaround is to use Regexp.try_convert. Regexp.try_convert accepts either a Regexp or an object that responds to #to_regexp; so this code works fine (and is in some ways better):

elsif re = Regexp.try_convert(o) # do something with o 

Still, that Regexp does not respond to #to_regexp surprised me. Does it surprise anyone else?