Re: printf: zero pad after the decimal a given amount

jidanni@jidanni.org wrote:
> Why is there no way to tell printf to zero pad like the right column:

One reason is that what you want is ill-defined. If we are going to tweak
sprintf to make it suit our personal preferences, I'd rather see a
conversion character that behaved just like %f if given a good number, but
returned the empty string if given either an empty string or undef (rather
than converting it to zero and then applying %f to the zero.)

> 0.1 :0.100
> 0.05 :0.050
> 0.03 :0.030
> 0.025 :0.025
> 0.02 :0.020
> 0.015 :0.015

Apparently you want to preserve non-zero digits even if that means going
beyond 3 digits right of the decimal. But why did you stop at 4?

0.014999999999999999444888

> 0.0125 :0.0125


0.0125000000000000006938893

How many consecutive zeros or nines are needed before you decide there are
enough to ignore what is the right of them?

Xho

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Re: printf: zero pad after the decimal a given amount

Quoth xhoster@gmail.com:
> jidanni@jidanni.org wrote:
> > Why is there no way to tell printf to zero pad like the right column:
>
> One reason is that what you want is ill-defined. If we are going to tweak
> sprintf to make it suit our personal preferences, I'd rather see a
> conversion character that behaved just like %f if given a good number, but
> returned the empty string if given either an empty string or undef (rather
> than converting it to zero and then applying %f to the zero.)
>
> > 0.1 :0.100
> > 0.05 :0.050
> > 0.03 :0.030
> > 0.025 :0.025
> > 0.02 :0.020
> > 0.015 :0.015
>
> Apparently you want to preserve non-zero digits even if that means going
> beyond 3 digits right of the decimal. But why did you stop at 4?
>
> 0.014999999999999999444888
>
> > 0.0125 :0.0125
>
>
> 0.0125000000000000006938893
>
> How many consecutive zeros or nines are needed before you decide there are
> enough to ignore what is the right of them?

It appears to me the OP wants either 3 s.f. after the point or 3 places,
whichever comes out shorter. Something like

sub fmt {
return
map /(\d*\.\d{3}\d*?)0*$/,
map /(\d*\.0*[1-9]\d\d)/,
map { sprintf "%.308f", $_ }
@_;
}

appears to work, but it's hardly pretty :(. The 308 is the number of
places required to represent DBL_MIN with 53-bit doubles; if your perl
is using 64-bit long doubles you will need 4932 instead.

Ben