[phobos] Proposal of StopWatch module

[Andrei Alexandrescu]

On 08/20/2010 05:47 PM, SHOO wrote:
> (2010/08/21 5:04), Andrei Alexandrescu wrote:
>> I think the code is ready for prime time, modulo the issues below. What
>> do you all think?
>>
>> Overall this is a good example of modern, idiomatic D code. Everything
>> is clear, simple, and in the right place. Congratulations, Shoo!
>>
>> *******
>>
>
>> Line 80: You could an assert or even an enforce here for TICKSPERSPEC.
>>
>
> A program does not work at all when a function failed in a module
> constructor. I'll set 0 for TICKSPERSEC when a function failed.
> And, had better I make TICKSPERSEC -> TicksPerSec?

ticksPerSec :o)

>  > Line 737: I'm afraid you can't put @trusted here because you don't know
>  > the safety level of BaseFunc and TargetFunc. You'll need to use @system.
>  >
>
> This is a source of worry very much.
> I hit on the idea that manage to do:
>
> private @safe void dummySafeFunc(alias FN)()
> {
> FN();
> }
>
> template isSafe(alias FN)
> {
> enum isSafe = is(typeof({dummySafeFunc!(FN)();}()));
> }
> @safe
> ComparingBenchmarkReturnValue comparingBenchmark(
> alias baseFunc, alias targetFunc, int CNT = 0xfff)()
> if (isSafe!baseFunc && isSafe!targetFunc)
> {
> ....
> }

I think that's a very good idea. In the long term we'll need to have 
some traits (either compiler-provided or deduced as above) and put them 
in std.traits.

> @system
> ComparingBenchmarkReturnValue comparingBenchmark(
> alias baseFunc, alias targetFunc, int CNT = 0xfff)()
> if (!(isSafe!baseFunc && isSafe!targetFunc))
> {
> ....
> }
>
> It is dirty slightly...
>
> May I put isSafe in std.traits?

Yes please.

>> Line 762: Beautiful idiom!
>>
>
> Thanks! But, I want to write like this:
> with (measureTime!((a){assert(a.seconds);}))
> {
> doSomething();
> }
>
> I don't want to name a nonuse variable.
> In this usage, I think that With is proper.
> But, this doesn't call destructor. (for bug 3516?
> Though I think that how to use is free.

It's definitely a bug. But note that in C++ an unused value will be 
destroyed at the end of expression, which makes sense. That means your 
idiom would need a named variable.


Andrei