Re: and then

[enterpoop.mit.edu!usc!cs.utexas.edu!mars.tsd.arlut.utexas.edu!gardner@ucb vax.Berkeley.EDU (Don Gardner)]

sampson@nosc.mil (Charles H. Sampson) writes:

>In article <19930406.143008.278@almaden.ibm.com> jnestoriak@vnet.IBM.COM write
s:
>>At a recent code inspection, someone suggested that I convert a
>>series of and's to and then's "for performance".  I expect that
>>90+% of the time all the conditions will be true anyway.  But is
>>it really true that and then will get better performance than
>>and?  I realize this is probably a compiler dependant question.
>>Also, I question the value of doing such a thing styllistically.
>>Any opinions?

>     My style is to use the boolean operators generally, reserving the
>short-circuit forms to document that the second operand should not be eval-
>uated under some circumstances.

I humbly suggest that you change your perspective.  When I encounter a
non-short-ciruit of the boolean operators I ask why both expressions
_must_ be evaluated; i.e., the short-circuit forms are the default and
the other forms are used only when both expressions must be evaluated.

Also, I avoid writing functions that have side effects.  Since (as
best I can reason at this early hour) both expressions need to be
evaluated only when both have side effects, I rarely use the
non-short-circuit forms.