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Posted by Michael Fesser on 01/07/08 17:23
..oO(Steve)
>"Michael Fesser" <netizen@gmx.de> wrote in message
>news:pmk4o3trg1johm5rcaiho04qaos5kbd5rg@4ax.com...
>
>> PHP uses lazy evaluation. As soon as the result is known, the evaluation
>> stops. Because of this behaviour you can write things like
>
>more pragmatic than lazy. if one condition is false, there is no possible
>way other &&'ed conditions could change that result...so, why continue the
>evaluation?
Correct, and one common name for that technique is "lazy evaluation" (or
"delayed evaluation"): the result of an expression is only calculated if
and when it's really necessary.
>most languages do it this way. of those that i've used, vb was the only one
>that continued to blindly evaluate conditions. it wasn't until vb.net that
>the AndAlso and OrElse short-circuit constructs were added - 'short-circuit'
>being even more descriptive than 'lazy' or 'pragmatic'.
AFAIK "short-circuit" is more related to logical expressions, whereas
"lazy evaluation" is the more general name and applies to many other
things as well.
Micha
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