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math.extras: adding the Möbius function.

db4
John Benediktsson 2014-12-23 20:08:23 -08:00
parent 56b95b09a1
commit 592764ded4
2 changed files with 19 additions and 4 deletions
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9
extra/math/extras/extras-tests.factor
View File

@ -148,3 +148,12 @@ IN: math.extras.test
{ 36100 } [ 20 iota sum-cubes ] unit-test
{ 36100 } [ 20 iota >array sum-cubes ] unit-test
{
{
1 -1 -1 0 -1 1 -1 0 0 1 -1 0 -1 1 1
0 -1 0 -1 0 1 1 -1 0 0 1 0 0 -1 -1
}
} [
30 [1,b] [ mobius ] map
] unit-test

14
extra/math/extras/extras.factor
View File

@ -4,10 +4,10 @@
USING: accessors arrays assocs assocs.extras byte-arrays
combinators combinators.short-circuit compression.zlib fry
grouping kernel locals math math.combinatorics math.constants
math.functions math.order math.primes math.ranges
math.ranges.private math.statistics math.vectors memoize parser
random sequences sequences.extras sequences.private sets sorting
sorting.extras ;
math.functions math.order math.primes math.primes.factors
math.ranges math.ranges.private math.statistics math.vectors
memoize parser random sequences sequences.extras
sequences.private sets sorting sorting.extras ;
IN: math.extras
@ -316,3 +316,9 @@ M: iota-tuple sum-squares
GENERIC: sum-cubes ( seq -- n )
M: object sum-cubes [ 3 ^ ] map-sum ;
M: iota-tuple sum-cubes sum sq ;
: mobius ( n -- x )
group-factors values [ 1 ] [
dup [ 1 > ] any?
[ drop 0 ] [ length even? 1 -1 ? ] if
] if-empty ;