From: Robert Klemme <bob.news@...>
Date: 2004-06-15T04:58:36+09:00
Subject: Re: assignment in conditional warning


"Rasputin" <one@nowhere.net> schrieb im Newsbeitrag
news:pan.2004.06.13.13.09.19.96019@nowhere.net...
> On Sat, 12 Jun 2004 16:36:27 +0200, Robert Klemme wrote:
>
> >
> > "Rasputin" <one@nowhere.net> schrieb im Newsbeitrag
> > news:pan.2004.06.11.20.50.29.369372@nowhere.net...
> >> Why in the world is there a warning, *even with brackets*, for
assignments
> >> in conditionals.
> >
> > There are not always warnings; it seems, it's only warned if the right
side
> > is a literal (i.e. a string or a number).  This is reasonable because it
is
> > likely that a comparison was meant.  After all, what do you gain by
doing
> >
> > if ( x = 10 )
> > end
> >
> > over
> >
> > if ( 10 )
> > end
> >
> > ?
>
> Actually, I don't think(not sure about this though) that Ruby actually
> knows, whether the number/string/whatever is in the literal(?) form, or
> if it's a return value from a function, beyond the parser level.

It's sufficient to know that during parsing, because this is a syntax
warning:

$ ruby -c -e 'if x = 10; puts "ja"; end'
-e:1: warning: found = in conditional, should be ==
Syntax OK

> Therefore, checking for it should be hard (or better yet, a waste of
> cycles).

With that argument you'd have to do assembler only - every syntax and other
check then is a waste of cycles.  Apart from that: the check is only done
once during compilation.  There's no runtime overhead at all.

> Personally, I think this warning should be allegated to the
>  $VERBOSE == true  level. (Those would be much easier to ignore)

I beg to differ.  Rather write code that does not give you warnings.  You
should at least consider the option that there is actually a good reason for
these warnings.

> What I wanted to do was check if an array contained a certain value, and
> do something with it, or else. Simple matter.

How then did you get a warning?

$ ruby -c -e 'a=%w{a b d c}; while a.include? "x"; p x; end'
Syntax OK

(no warning here)

> Just a mite obfusticated, if at all. So I think the stuff above made
> sense... (It was short and to the point anyway (i think...))

Which stuff?  Did you post your code?  I can't see it at the moment.  Please
show us the code; I bet we can then discuss this better.

> But this is just going to be a matter that will be discussed my many
> without anyone changing their minds (not really they won't).

Well, I'm open to change my mind if you provide better arguments in favor of
your position.  It's just that I can't see them at the moment.

> I mean should we go for short elegant code irritating-waste-of-spacers.

I don't know what's irritating about

x = get_x()

if x == "foo"
  puts "ja"
end

I find this more irritating:

if ( x = get_x() ) == "foo"
  puts "ja"
end

I prefer to have this only with loops because in that case it's a real gain
in elegance that can't be achieved otherwise.  But for if/unless it's plain
superfluous.

Regards

    robert