On Sat, 3 Mar 2018, Ian Lepore wrote:
On Sat, 2018-03-03 at 22:49 +0200, Konstantin Belousov wrote:
,,,
BTW mstosbt() and other functions have weird bracing in the formula. I
think that the formula as calculated by the C operator precedence is
fine, i.e. multiplication is done before right shift. But the bracing
is redundand then, because the '()' pair next to the return () braces by
inclusion is tautological.
Oh, on looking closer, it's not a paste-o, I just didn't put the
closing paren where I had intended to for making it clear the shift
happens last. ?(So almost everyone except me is still going to think a
fix has redundant parens.)
It is a good example of how redundant parentheses reduce readability.
Redundant parentheses make the non-redundant parentheses hard to see.
The most important ones are for _ms * (x / 500) (where x =
((uint64_t)1 << 63)). These are needed since the natural expression
_ms * x / 500 would overflow since it is evaluated left to right. Then
you want to add redundant parentheses for _ms * (x / 500) >> 32,
although both left to right evaluation and operator precedence work
right for that. Then style(9) requires redundant parentheses for the
return value. Normally I would parenthesize x * y >> z since I don't
remember the precedence of '>>' and suspect it is broken (*), but here
there are too many other parentheses.
(*) The precedence of '>>' is indeed broken. It is like a division operator
so should be at the same level or 1 lower. But it is 2 lower (+ and - are
in between). So x + y * z means x + (y * z), but x + y >> z means
(x + y) >> z. So x + (y >> z) needs parentheses, and (x + y) >> z should
be parenthesized since it is surprising that its parentheses are redundant.
Bruce
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