From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-05-31T11:30:30+09:00
Subject: Re: Introducing the "it" keyword

Eleanor McHugh wrote:
> On 29 May 2007, at 14:17, Gregory Seidman wrote:
>> Looking at it from a different perspective, consider whether any proposed
>> change to Ruby moves it closer to language X (which I'm equating to Perl)
>> or closer to language Y (which I'm equating to Lisp). Moving toward X 
>> means
>> making things easy to express tersely at the expense of overall 
>> readability
>> and maintainability. Moving toward Y means simplifying the expression of
>> things using existing syntax and functionality. I claim that we should
>> strive to avoid shortcuts that bring Ruby closer to X and strive to solve
>> our problems in ways that bring Ruby closer to Y.
> 
> I should just point out that Ruby is not Lisp, and that whilst Lisp has 
> many admirable traits, there are many Ruby programmers who like it that 
> way.
> 
> On to the topic in question: the idea of the OP that we should be able 
> to write
> 
>>     return it if |v + 1| < 10
> 
> addresses a very real issue as the fragments
> 
>     t = f(n)
>     return t if t != x
> 
> and
> 
>     t = f(n)
>     return t unless t == x
> 
> pop up regularly in my code. As the whole bundle is a single operation 
> it _should_ be possible to write it in atomic form along the lines of
> 
>     return %$ if f(n) != x
>     return %$ unless f(n) == x
>     puts %$[0], %$[1], %$[2] if f(n) > 0
>

While I realize the Ruby is not C, I think that some of the style 
guidelines for C should still apply in Ruby.  One of the ones that was 
very important was to make each statement do only one thing.  Your 
example of setting a temporary variable to an amount on one line and 
then testing that variable on the second line is much easier to read, 
and understand, quickly than your statements like 'return %$ unless f(n) 
== x'.  This becomes even more important when the test is even more 
convoluted such as checking for the position of a string in another 
string and returning if it is in a specific location.


> where %$ is a placeholder for substitution of the value returned by f(n).
> 
> I've used %$ in these examples due to the conceptual similarity to 
> substitution in the sprintf method and the use of subscripts adds the 
> possibility of consuming multiple return values, although I'm not 
> suggesting it's a _good_ notation :) Whatever the specific token, I 
> think punctuation would be a better choice than a keyword because it 
> focuses the eye on the fact that something special is happening and 
> makes explicit that neither a local variable nor a function call is 
> being evaluated where the substituted value is being used. Under the 
> hood the interpreter could avoid messing with local variables, the 
> result would be generated just once, it could be garbage collected 
> immediately on completion and probably all kinds of cleverness could be 
> applied.
> 
> Of course this approach fails to solve other common cases such as
> 
>     return f(n), f(m) if f(n,m) == x
> 
> 
> Ellie
> 
> Eleanor McHugh
> Games With Brains
> ----
> raise ArgumentError unless @reality.responds_to? :reason
> 
>