From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2003-07-17T02:09:54+09:00
Subject: Re: Other languages' features in Ruby

In article <D3E034C6-B798-11D7-ACD8-00039381462A@thingmagic.com>,
Ben Giddings  <ben@thingmagic.com> wrote:
>Hrm, well I'm a Ruby/Java/C/C++/Python/Perl/Lisp/Javascript/PHP... 
>um... and others programmer.
>
>On Wednesday, July 16, 2003, at 09:36  AM, Peter Hickman wrote:
>> We've had Java/C++/Whatever programmers ask for type checking, 
>> operator overloading, polymorphism and a whole host of compile time 
>> checking.
>
>Is there a good way to get what type checking does for you?  

Unit testing.

>Maybe some 
>kind of ruby-lint program that looks through your source code and tries 
>to see if you're making odd assumptions about the type of your 
>variables?  Or (much more useful in my opinion) something that will try 
>to catch the use of uninitialized variables?  

Well, that already happens:

 def foo(bar)
  puts a
 end

 foo(1)
 NameError: undefined local variable or method `a' for #<Object:0x401d1ce0>
        from (irb):5:in `foo'
        from (irb):8

....OK, admitedly, that's at runtime, but that's why you want unit tests.

>This would be helpful in 
>catching typos, like calling the class variable @my_var, but ending up 
>using it as @myvar.
>
>> Lisp programmers have enquired about macros (occasionally).
>
>Are there good ways of doing what Lisp macros do for you?

Perl has input filters (see the perlfilter docs) that sort of act like a pre-processor 
for yout source.  This was originally intended for encrypting source-code, but now is 
used for lots of other purposes.  Perl even has a command line argument (-p, I believe) 
that will pass the source through the c pre-processor before Perl interprets it.

I wonder how difficult it would be to do input filters for Ruby?

On the otherhand, it's probably not a feature needed in Ruby as much as it is in Perl.

>
>Maybe the fact people keep asking for this points to the need for a set 
>of FAQs that pick features from other languages and explain if they 
>exist in Ruby, how to use them, and if they're not there, why not.  
>Maybe such a FAQ already exists, I don't know.
>
>Ben
>
>

Phil