From: Robert Klemme <shortcutter@...>
Date: 2006-04-12T22:05:46+09:00
Subject: Re: Style question: if !x vs. unless x

2006/4/11, David Brady <ruby_talk@shinybit.com>:
> Hi all,
>
> One of the coolest things for me about learning ruby is that it's the
> first language I've learned in a decade where I actually had to learn a
> new language.  Once you know C/C++, you can pick up Java, PHP, perl,
> Python, and even VB without really having to learn new grammar... you
> just learn where the braces and dollar signs go.  One of the joys of
> ruby is that when I find myself using a klunky grammar construct, there
> is often an elegant solution if I will just surrender my C++ thinking style.
>
> That paragraph could spark a thread of its own, but in this case, its
> lead-up for a simpler question.  Which do you find more readable:
>
> # this version
> if !correct
>   handle_error
>   do_some_other_thing
> end
>
> # or this version
> unless correct
>   handle_error
>   do_some_other_thing
> end
>
> When dealing with single-lines, I find the inverted construct to be MUCH
> more readable:
>
> handle_error unless correct

In fact I'd usually make the above a single liner by using exceptions:

raise SomeError unless correct
# continue normal processing

alternative

correct or raise SomeError
# continue normal processing

> but when I have to make a block, my C++ instincts really prefer the "if
> !" version.

I usually use "unless" if there is a single negated expression and use
"if" otherwise. No distinction with regard to single line or block.

> Hmm, I just discovered this syntax, and for small blocks, I prefer it
> greatly:
>
> ( handle_error; do_some_other_thing ) unless correct

I don't like that. Use the normal if ... then .. end - that looks
better, to me at least.

Kind regards

robert

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