From: Daniel Carrera <dcarrera@...>
Date: 2003-04-09T07:18:39+09:00
Subject: The "!" and "?" characters.

One of the things I like about Ruby is that it can use ! and ? in method 
names.  However, it seems that there are still limits to what can be 
done.

I need a 'factorial' method, and I thought it'd be cute if the syntax was 
"n.!" because it's so close to "n!".  But Ruby doesn't let me do that.

# This one works:
>> class Fixnum
>>     def f  # Factorial 
>>         self < 0 and return -1  # Error code.
>>         self ==0 and return  1 
>>         self * (self-1).f
>>     end
>> end
>> 5.f
=> 120

This is cool.  But it'd be cooler if I could write 'def !' and '5.!'.
But 'def !' causes a parse error.

Now my question:
Does anyone know why 'def !' causes a parse error?

Thanks.
-- 
Daniel Carrera
Graduate Teaching Assistant.  Math Dept.
University of Maryland.  (301) 405-5137
--
quintessence: quintessence (kwin-TES-ens) noun
   1. The pure, concentrated essence.