I've got this recollection of there being a hex floating format specifier for s/printf; which I've never had a use for; but now I have, I cannot find any reference to it.

Did I imagine it? Is it a recollection from some other language?

perlfunc from 5.22 documents %a as "hexadecimal floating point", and %A as "like %a, but using upper-case letters". 5.18 does not know about %a and %A.

Update: Listed as new feature in perldelta from 5.22.0.

Alexander

Thanks afoken (and anonymonk). I'd begun to think I'd imagined it. I didn't think to look there (5.22) because it seems like a much older memory.

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With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this

In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

C:\>perl -MData::Float="float_hex" -le "print float_hex(1 / 9);"
+0x1.c71c71c71c71cp-4
[download]

Thanks for that. I won't be using it directly as I don't need its flexibility and I'll need to extend it for my extended precision numbers; but it made a nice reference.

This is my version for standard doubles:

sub fmt{
    my $bin = unpack 'Q', pack 'd', $_[0];
    my $sign = ( $bin & 0x8000000000000000 );
    my $exp  = ( $bin & 0x7FF0000000000000 ) >> 52; $exp -= 1023;
    my $mant = ( $bin & 0x000FFFFFFFFFFFFF );
    sprintf "%s0x1.%xp%d", ( $sign ? '-' : '' ), $mant, $exp;
}
[download]

Some outputs:

C:\test>fmt -- -1/9
-0x1.c71c71c71c71cp-4

C:\test>fmt -- 1/9
0x1.c71c71c71c71cp-4

C:\test>fmt -- 1/3
0x1.5555555555555p-2

C:\test>fmt -- 1/11
0x1.745d1745d1746p-4

C:\test>fmt -- "( 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
+ + 1/512 + 1/1024 + 1/2048 + 1/4096 + 1/8192 + 1/16384 + 1/32768 + 1/
+65536 + 1/131072 + 1/262144 + 1/524288 )"
0x1.ffffc00000000p-1
[download]

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this

In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

An example for the curious:

$ perl -E'say sprintf "%a", 1/9'
0x1.c71c71c71c71cp-4
[download]

Never mind: I found a non-Perl reference that gave the information I required: "The suffix ‘p-4’, which represents the power of two, written in decimal: 2-4."

Look as I might, I cannot find anything in the docs or articles linked below that says whether the exponent in the hex floats is also in hex?

EDIT: I'm sure I misunderstood the OPs question. This can be reaped.

Are you going from int to hex? If not, can you clarify?

perldoc -f sprintf

perl -E '$x="200";$y=sprintf("%.02x", $x); say $y;'
c8
[download]

-stevieb