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math.extras: adding map-kahan-sum.

db4
John Benediktsson 2013-10-13 08:40:50 -07:00
parent b9df0a7582
commit d06dc0996d
1 changed files with 12 additions and 3 deletions
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extra/math/extras/extras.factor
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@ -290,7 +290,16 @@ M: real round-away-from-zero
] reduce nip max ] reduce nip max
] if ; inline ] if ; inline
<PRIVATE
: kahan+ ( c n elt -- c' n' )
rot - 2dup + [ -rot [ - ] bi@ ] keep ;
PRIVATE>
: kahan-sum ( seq -- n ) : kahan-sum ( seq -- n )
[ 0.0 0.0 ] dip [ [ 0.0 0.0 ] dip [ kahan+ ] each nip ;
rot - 2dup + [ -rot [ - ] bi@ ] keep
] each nip ; : map-kahan-sum ( ... seq quot: ( ... elt -- ... n ) -- ... n )
[ 0.0 0.0 ] 2dip [ 2dip rot kahan+ ] curry
[ -rot ] prepose each nip ; inline