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Re: strtoul (was Re: [PATCH] Fcntl constants speedup)

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Nicholas Clark
December 19, 2000 14:33
Re: strtoul (was Re: [PATCH] Fcntl constants speedup)
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On Tue, Dec 19, 2000 at 09:25:47PM +0000, Nick Ing-Simmons wrote:
> Nicholas Clark <> writes:
> >> 
> >> But I don't see where looks_like_number() lets things with ',' in through
> >> to be converted ... 
> >
> >I think that I was unclear. Jarkko was suggesting roll our own strtol
> >(etc) for perl6.
> >I was only thinking in terms of roll our own routine in 5.7 for sv_2[iun]v
> >to call. 
> So was I - looks_like_number is doing most of the work already, having it 
> tally up the digits into an UV as it goes makes a lot of sense to me.

I'll be even happier if the arm backend optimiser likes the idea of *10

total ||= total << 2;
total = new_digit + total << 1;

as that's 2 machine instructions, 2 clock cycles, whereas *10 is at least

Just 1 more advantage of base being constant at compile time.
I think can get the value out of looks_like_number pretty much for free.
(and I think I know how to pre-empt overflow cheaply)

> It is less clear that we want the hassle of the NV case.

I wasn't thinking of the NV case.
As I mailed Jarkko privately recenmtly, I don't like floting point numbers.
I had 4 different versions of "500" once, but I only found out that this
was the cause of my problem after 2 or 3 days of pain.

Also, numconvert.t getting upset with 18446744073709551615 and
18446744073709551616 as they go too and from floating point (particulary
long double - still not solved, not even sure it it's soluable)
remind me that floating point is horrible.

I would have said "I like chars. There are only 256 of them." But someone's
removed that safe haven now.

I was thinking something like

int son_looks_like_number (SV * sv, UV *value);
that returns flags about what it found out in the int, and the value in
*value if the pointer is non null, and the value doesn't overflow.
(flags include "minus", "erk we've overflowed the UV", "saw a decimal point"
"saw e notation" and "infinity" as now; the UV would return the abs value)

Nicholas Clark

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