Rosetta Code

Posit numbers/decoding: Difference between revisions

Page Discussion

Posit numbers/decoding (view source)

Revision as of 18:14, 19 September 2023

89 bytes removed ,  8 months ago
m
→‎{{header|Julia}}: simplify zero handling
(julia example)
m (→‎{{header|Julia}}: simplify zero handling)
Line 23:
""" From posithub.org/docs/Posits4.pdf """
function Base.Rational(p::PositType3)
s = signbit(p.bits) # s for S signbit, is 1 if negative
pabs = p.bits << 1 # shift off signbit (adds a 0 to F at LSB)
pabs == 0 && return s ? 1 // 0 : 0 // 1 # if p is 0, return 0 if s = 0, error if s = 1
expsign = signbit(pabs) # exponent sign from 2nd bit now in MSB location
k = expsign == 1 ? leading_ones(pabs) : leading_zeros(pabs) # regime R bit count
scaling = 2^p.es * (expsign == 0 ? -1 : 1)
pabs <<= (k + 1) # shift off unwanted R bits
pabs >>= (k + 2) # shift back without the extra LSB bit
fsize = p.numbits - k - p.es - 2 # check how many F bits are actually explicit
fsize <= f0 =&& fsize >return 0 ?// (pabs1 & (2^fsize - 1)) // 2^fsize : 0 # Get F value. Can be# missing ->F is 0
f = (pabs & (2^fsize - 1)) // 2^fsize # Get F value. Can be missing -> 0
e =
e = pabs >> fsize fsize > 0 ? (pabs >> (fsize)) : # Get E value. Can be up to p # Get E value.es bits
pw = (1 - 2s) * (scaling * k + e + s)
pabs * 2^(p.es - p.numbits - k - 2) # implicit missing bits correction
return pw >= 0 ? ((1 - 2s3s) + f) * 2^pw // 1 : (scaling(1 *- k3s) + ef) +// s2^(-pw)
return pw >= 0 ? ((1 - 3s) + f) * 2^pw // 1 : ((1 - 3s) + f) // 2^(-pw)
end
 
@show Rational(PositType3(16, 3, 0b0000110111011101)) == 477 // 134217728
</syntaxhighlight>{{out}} <pre> Rational(PositType3(16, 3, 0x0ddd)) == 477 // 134217728 = true</pre>
 
 
=={{header|raku}}==
Wherrera
4,102

edits

Retrieved from "https://rosettacode.org/wiki/Special:MobileDiff/360002"