From: sto.mar@...
Date: 2013-01-06T17:33:51+09:00
Subject: Re: Best practice for &&, ||, and, or

Am 06.01.2013 05:56, schrieb Jan E.:
> Dave Aronson wrote in post #1091178:
>> No!  No!  1000.times :no!  ;-)
>>
>> Consider the difference between "x = true && false" and "x = true and
>> false".  Since && has HIGHER precedence than =, "x = true && false" is
>> equivalent to "x = (true && false)", just as you might expect.
>
> Why would I expect that? Why would I even *use* assignments in "if"
> statements?

I think Dave was not talking about an assignment in an if statement,
just a "pure" assignment of a boolean expression to a variable.

[...]

> Maybe my programming style is totally out of fashion, but my "if"
> statements usually look like this:
>
> if <some expression> and (<some expression> or <some expression>)
>    ...
> end

[...]

> When I want to do "magic" like
>
> var = val || alt
>
> then I do use &&/||. But this is a very different context.

What I do not like about this approach is that the used operators
depend on the context (condition in if statement / condition assigned
to a variable), not on the purpose (condition vs. control flow).

Every time you want to refactor an if statement by pulling out the
condition into a variable you have to change operators:

   if condition_one and condition_two
     ...
   end

becomes

   valid = condition_one && condition_two
   if valid
     ...
   end

No "magic" is involved here.

Regards,
Marcus


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