Re: why use pow(x, 2)?
Re: why use pow(x, 2)?
- Subject: Re: why use pow(x, 2)?
- From: Jens Alfke <email@hidden>
- Date: Mon, 2 Nov 2009 15:06:58 -0800
On Nov 2, 2009, at 2:01 PM, Chris Williams wrote:
But it still does leave the style question: is pow(x,2) clearer than
x*x?
For arbitrary values of "x" they won't even give the same results.
(Consider if the value being squared were "q++".)
And if the value being squared contains function calls, the compiler
will usually not be able to optimize away the second call, not unless
it knows that the function is 'pure'. For instance, it could not
optimize
foo()*foo()
into a single call to foo() followed by a multiplication, because for
all it knows, foo() has side effects or otherwise doesn't always
return the same result.
(Using an inline 'sqr' function gets around these problems, though,
because the function's argument is only evaluated once.)
—Jens_______________________________________________
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