On Wed, 17 Nov 2010 17:46:57 -0500, Don Clugston
<[email protected]> wrote:
(1) Add two necessary functions to std.math:
// Rounds x to the nearest int or long using the currently selected
rounding mode
// (MUCH faster than cast(int)).
Why isn't this the default, i.e. why doesn't cast(int) do this?
Because C stuffed up in a major way, and we have to live with it.
Intel has tried THREE TIMES to fix C's mistake, by making hardware
changes and adding new instructions to their CPUs.
Please use full words when abbr is not absolutely obvious and/or the
gain in typing is small (esp for rarely used functions).
(also sgngamma --> signgamma)
I didn't invent the name. sgn is the signum function. See, for example,
http://en.wikipedia.org/wiki/Sign_function
To an uninitiated reader this may look like "random int" and "random
long".
Ugh, you're right.
Could we define this instead?
N roundTo(N)(real x) if (isIntegral!N);
That sounds a bit too formal. I would expect that to perform some
exact form of rounding (certainly not round-to-nearest, which seems
irrational to our uninitiated reader). I would also expect it to do
something sensible when the value is > int.max.
This function should really be an intrinsic, and it only makes sense
for int and long.
fastRoundInt(real x)
fastRoundLong(real x)
?
A bit clumsy, but should be unambiguous.
Personally, I've already switched to using roundTo!T in my code. The
function is over in std.conv, behaves as expected and supports a wide
range of types. In contrast std.math has a multitude of functions (lround,
lrint, rndtol) some of which have _never_ been implemented (lround) and
others appear to be aliases of each other (lrint, rndtol). (This may just
be incorrect documentation as rndtonl and rndtol are described
differently). This is to say nothing of the floating point rounding
functions (nearbyint, rint, round, rndtonl). Given that we have control
over the floating point rounding mode, is there a reason we need anything
more than round and roundTo!T?
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