From: Joel VanderWerf <vjoel@...>
Date: 2002-09-05T13:55:28+09:00
Subject: Re: Ruby aesthetics

Gavin Sinclair wrote:
>>Gavin Sinclair wrote:
>>...
>>
>>>My frame-of-reference for good language design is Ruby.  So compared
>>>to Ruby, I would add:
>>> - list comprehensions
>>> - calling procs would look like real functions, not arrays!
>>>     e.g. id = proc { |x| x };  id(12)   # not id[12]
>>
>>This bothered me a little, OUAT (once upon a time :), but not now. I
>>like being able to use procs and hashes interchangeably. This makes it
>>possible to think of a hash as a function in the sense of a set of
>>ordered pairs:
>>
>>   succ_mod_3    = {0=>1, 1=>2, 2=>0}
>>   succ_integer  = proc {|x| x+1}
>>
>>   def cycle(succ_map)
>>     x = 0
>>     10.times do
>>       print x
>>       x = succ_map[x]
>>     end
>>   end
>>
>>   cycle succ_mod_3    # ==> 0120120120
>>   cycle succ_integer  # ==> 0123456789
> 
> 
> Hey, nice!  I like that.  Although using an iterator would be more
> Ruby-ish and flexible, wouldn't it?  Besides, we've seen Perl and Python
> make a real hash of hashes (sorry...)

Okay, with iterator support:

   def cycle(succ_map=nil, &block)
     succ_map ||= block
     x = 0
     10.times do
       print x
       x = succ_map[x]
     end
   end

   cycle do |x| x-1 end  # ==> 0-1-2-3-4-5-6-7-8-9

...and the hash and proc arguments still work as well.

>>If you want to use procs and methods interchangeably, you have a little
>>more work, but not much--just apply #method.
> 
> 
> Correct, but (please excuse my possibly ignorance and definite
> inexperience) I think it's a bit messy.  I just can't see the uniformity. 
> It'll come in time... and in the meanwhile, it doesn't get in my way.

How's this:

   def add_5 x
     x + 5
   end

   cycle method(:add_5) # ==> 051015202530354045

(You could even change #cycle to check if its first arg is a symbol...)

The really hoopy thing about dynamic typing is that all we assume about 
the succ_map is that it supports #[], so this snippet will work with, 
say, PStore, or a database class that has #[].