From: gwtmp01@...
Date: 2006-06-02T08:43:56+09:00
Subject: Re: Adding an Increment Operator?


On Jun 1, 2006, at 7:15 PM, Dave Howell wrote:

> As Logan pointed out in a different thread:
>
>> % cat increment.rb
>> class Fixnum
>>   def increment
>>     self = self + 1
>>   end
>> end
>>
>> a = 1
>> a.increment
>>
>>
>> % ruby increment.rb
>> -:13: Can't change the value of self
>>     self = self + 1
>>           ^
>
> So, how WOULD I create an .increment operator? I get why I can't  
> put it in class Fixnum (well, I think I know why); Fixnums are  
> symbol-ish-ly unalterable. 5.increment should fail, for sanity's sake.

Fixnum objects aren't containers for integer values.  Each Fixnum  
object represents a different integer via a one-to-one mapping. So  
just as you can't increment the integer 1 you can't increment the  
Fixnum that represents the integer one.

The concept of 'the next integer' works though and that is available  
via Fixnum#succ

Ruby doesn't allow you to use assignment to bind self to a new object  
either so
   self = <anything>
is a syntax error.


> So I have to add .increment to class . . . hmm. I can't add it to  
> variables; they're just references. But I want my_var.increment to  
> change 'my_var' so that it references the next integer in line.

myvar = myvar.succ

Gary Wright