From: Rich Morin <rdm@...>
Date: 2007-05-26T01:23:59+09:00
Subject: Re: Replacement idiom for "list_or_nil.to_a"?

Thanks for the suggestions!  Here's a summary, with comments:

> foo.to_a.each            {|value| ... }

  This is what I was using.  It's nice to know that it's not
  going away, after all.


> foo.to_a.each            {|value| ... } if foo

  This moves the "if" clause away from the iteration, which
  might make it harder to see.  Also, it evaluates foo twice
  (could duplicate side-effects if foo is a method or be a
  performance issue id evaluating foo is expensive).


> foo and foo.each         {|value| ... }

  A bit wordy and obscure.  Also, it evaluates foo twice.


> class NilClass
>   def each; self; end
>   include Enumerable
> end
>
> foo.each                 {|value| ... }

  This shortens the usage code, but I don't like playing with
  the definition of NilClass.  Specifically, this might confuse
  a human reader or get in the way of code that already expects
  the current behavior.


> (foo || []).each         {|value| ... }

  This smells like line-noise, but is otherwise quite adequate.


> (foo || VOID).each       {|value| ... }
> (foo || void).each       {|value| ... }

  Aside from the line-noise issue, these seem similar to me.
  Both require the use of a supplementary definition, however,
  which the reader might have to loop up.


> Array(foo).each          {|value| ... }

  This seems like an improvement, from a clarity standpoint.


My preference, at this point, is for either:

> foo.to_a.each            {|value| ... }

> Array(foo).each          {|value| ... }

I think I prefer the latter, from a clarity standpoint.  Also,
the fact that to_a is being deprecated in other contexts might
confuse some readers.

If foo is a BIG array, there might be performance differences
between these two, but I'm loathe to second-guess interpreter
implementation issues of this sort...

-r
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http://www.cfcl.com/rdm            Rich Morin
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