From: "Ara.T.Howard" <ahoward@...>
Date: 2004-06-13T01:03:39+09:00
Subject: Re: assignment in conditional warning

On Sat, 12 Jun 2004, Robert Klemme wrote:

>> Most novice programmers would want to use that.
>
> I beg to differ: the *only* reasonable usage of assignment in conditionals
> is with "while" and "until", i.e. looping constructs, like in:
>
> while ( line = gets )
>  line.chomp!
>  # do something with current line
> end
>
> Assignment in "if" and "unless" is totally superfluous.  It obfuscates code
> and is not needed at all.  Every "if ( x = expression )" can be converted to
>
> x = expression
> if x
> ...
>
> which is *much* clearer and cleaner IMHO.  Alternatively you can do this in
> some cases:
>
> x = expression and puts "yes"

IMHO the above fails apart when you are testing compound datastructures using
assignment to deconstruct the structure into more manageable peices in the
test.  which is cleaner/clearer?

1)

   tuples = db.execute sql

   raise "something terrible has happened in the database" unless
     (tuple = tuples.first) and (answer = tuple.first) and (answer == 42)

2)

   tuples = db.execute sql

   raise "something terrible has happened in the database" unless
     tuples.first and tuples.first.first and tuples.first.first == 42

3)

   tuples = db.execute sql

   tuple = tuples.first
   answer = tuple.first

   raise "something terrible has happened in the database" unless
     answer == 42



i can seem someone chosing 1 or 3 from above.  but when the code size starts
to grow i think most programmers, given a choice between two clear statements,
chose the shorter one and that, in fact, the __length__ of a statement
relative to it's source file is directly related to it's understand-ability.
especially consider the case where the variables 'tuple' and 'answer' are not
used except for testing purposes - isn't it better to isolate them to the
conditional expression then?  if course, you don't have to name them at all
(2), but that IS obfuscated!

cheers.

-a
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