Rosetta Code

Posit numbers/decoding: Difference between revisions

Page Discussion

Posit numbers/decoding (view source)

Revision as of 16:45, 25 January 2024

1,633 bytes added ,  3 months ago
m
→‎{{header|Wren}}: Changed to Wren S/H
(Add John Gustafson's Mathematica code)
m (→‎{{header|Wren}}: Changed to Wren S/H)
 
(5 intermediate revisions by 2 users not shown)
Line 265:
</pre>
 
=={{header|rakuRaku}}==
{{trans|Mathematica}}
<syntaxhighlight lang=raku>=begin LICENSE
Copyright © 2017 John L. Gustafson
 
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sub-license, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
<syntaxhighlight lang=raku>unit role Posit[UInt $N, UInt $es];
 
This copyright and permission notice shall be included in all copies or substantial portions of the software.
has UInt $.UInt;
method sign { self.UInt > 2**($N - 1) ?? -1 !! +1 }
 
THE SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
method FatRat {
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
return 0 if self.UInt == 0;
NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES, OR OTHER LIABILITY,
my UInt $mask = 2**($N - 1);
WHETHER IN AN ACTION OR CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
return Inf if self.UInt == $mask;
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
my UInt $n = self.UInt;
=end LICENSE
my $sign = $n +& $mask ?? -1 !! +1;
my $r = $sign;
$n = ((2**$n - 1) +^ $n) + 1 if self.sign < 0;
my int $count = 0;
$mask +>= 1;
my Bool $first-bit = ?($n +& $mask);
repeat { $count++; $mask +>= 1;
} while ?($n +& $mask) == $first-bit && $mask;
my $m = $count;
my $k = $first-bit ?? $m - 1 !! -$m;
$r *= 2**($k*2**$es);
return $r unless $mask > 1;
$mask +>= 1;
$count = 0;
my UInt $exponent = 0;
while $mask && $count++ < $es {
$exponent +<= 1;
$exponent +|= 1 if $n +& $mask;
$mask +>= 1;
}
$r *= 2**$exponent;
my $fraction = 1.FatRat;
while $mask {
(state $power-of-two = 1) +<= 1;
$fraction += 1/$power-of-two if $n +& $mask;
$mask +>= 1;
}
$r *= $fraction;
 
constant nbits = 16;
return $r;
constant es = 3;
constant npat = 2**nbits;
constant useed = 2**2**es;
constant minpos = useed**(-nbits + 2);
constant maxpos = useed**(+nbits - 2);
constant qsize = 2**((nbits-2)*2**(es+2)+5).log2.ceiling;
constant qextra = qsize - (nbits - 2)*2**(es+2);
 
constant posit-range = 0..^2**nbits;
 
sub twoscomp($sign, $p) { ($sign > 0 ?? $p !! npat - $p) mod npat }
 
sub sign-bit(UInt $p where posit-range) { +$p.polymod(2 xx nbits - 1).tail }
sub regime-bits(UInt $p where posit-range) {
my $q = twoscomp(1 - sign-bit($p), $p);
my @bits = $q.polymod(2 xx nbits - 1).reverse;
my $bit2 = @bits[1];
my @temp-bits = flat @bits[1..*], 1 - $bit2;
my $npower = @temp-bits.first(1 - $bit2, :k) - 1;
@bits[1..($npower+1)];
}
sub regime-value(@bits) { @bits.head ?? @bits.elems - 1 !! -@bits; }
sub exponent-bits(UInt $p where posit-range) {
my $q = twoscomp(1 - sign-bit($p), $p);
my $startbit = regime-bits($q).elems + 3;
my @bits = $q.polymod(2 xx nbits - 1).reverse;
@bits[$startbit-1 .. $startbit-1 + es - 1]
}
sub fraction-bits(UInt $p where posit-range) {
my $q = twoscomp(1 - sign-bit($p), $p);
my $startbit = regime-bits($q).elems + 3 + es;
my @bits = $q.polymod(2 xx nbits - 1).reverse;
@bits[$startbit-1 .. *];
}
 
sub p2x(UInt $p where posit-range) {
my $s = (-1)**sign-bit($p);
my $k = regime-value regime-bits $p;
my @e = exponent-bits $p;
my @f = fraction-bits $p;
@e.push: 0 until @e == es;
my $e = @e.reduce: 2 * * + *;
my $f = @f == 0 ?? 1 !! 1.FatRat + @f.reduce(2 * * + *)/2**@f;
given $p {
when 0 { 0 }
when npat div 2 { Inf }
default { $s * useed**$k * 2**$e * $f }
}
}
 
dd p2x 0b0000110111011101;
CHECK {
</syntaxhighlight>
use Test;
# example from L<http://www.johngustafson.net/pdfs/BeatingFloatingPoint.pdf>
is Posit[16, 3]
.new(UInt => 0b0000110111011101)
.FatRat, 477.FatRat/134217728;
}</syntaxhighlight>
 
{{out}}
 
<pre>okFatRat.new(477, 1 -134217728)</pre>
 
=={{header|Wren}}==
{{libheader|Wren-fmt}}
{{libheader|Wren-big}}
<syntaxhighlight lang="ecmascriptwren">import "./fmt" for Conv, Fmt
import "./big" for BigRat, BigInt
 
PureFox
9,476

edits

Retrieved from "https://rosettacode.org/wiki/Special:MobileDiff/360016...360022"