Evaluation of complex conditions

Pete pete at mollysrevenge.com
Thu Oct 6 12:34:13 CDT 2011


Thanks Ken.  Like you, I do tend to put parens around individual conditions
in a multi-condition if statement. I guess as long as all the conditions are
in parens, it won;t matter if parens change the order of evaluation.

Thanks to all for the clarifications.

Pete
Molly's Revenge <http://www.mollysrevenge.com>




On Thu, Oct 6, 2011 at 10:14 AM, Ken Ray <kray at sonsothunder.com> wrote:

>
> On Oct 6, 2011, at 11:40 AM, Pete wrote:
>
> > Thanks Alex, makes total sense with the examples you provided.
> >
> > The only remaining question in my mind is if the use of parens changes
> > anything - a post yesterday suggested that putting a condition in parens
> > causes it to be evaluated ahead of the other conditions but I can't make
> > that happen in your example.  I suspect confusion between precedence and
> > evaluation again.
>
> There are certain times where parens are necessary (I just wish I could
> remember specifically where and when). It *is* a good practice to put
> expressions in parens for readability, especially when it comes to working
> with objects. Compare:
>
> if the name of button 1 contains "test" and the name of button 2 contains
> "test" then
>
> if (the name of button 1 contains "test") and (the name of button 2
> contains "test") then
>
> The second is definitely more readable. Personally, I put parens around
> most/all expressions since that is the way it is with most other languages.
> For example, we *can* do this:
>
> if 2 + 3 = 5 then
>  answer "Right"
> else
>  answer "Wrong"
> end if
>
> but if you try that the equivalent in JavaScript:
>
> if 2 + 3 == 5 {
>  alert("Right");
> } else {
>  alert("Wrong");
> }
>
> you won't get an alert dialog. You have to put the expression in parens to
> make it work:
>
> if (2 + 3 == 5) {
>  alert("Right");
> } else {
>  alert("Wrong");
> }
>
> So my suggestion is to parenthesize everything for both readability and
> developing a cross-compatible coding style, even if it doesn't affect (for
> LiveCode) how the engine parses the expression.
>
>
> Ken Ray
> Sons of Thunder Software, Inc.
> Email: kray at sonsothunder.com
> Web Site: http://www.sonsothunder.com/
>
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