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math.functions: adding generalized signum function. Fixes #509.

db4
John Benediktsson 2012-05-03 14:44:10 -07:00
parent af8f23a78c
commit 31c7bd8e86
3 changed files with 16 additions and 0 deletions
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4
basis/math/functions/functions-docs.factor
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@ -336,3 +336,7 @@ HELP: roots
HELP: sigmoid HELP: sigmoid
{ $values { "x" number } { "y" number } } { $values { "x" number } { "y" number } }
{ $description "Outputs the sigmoid, an S-shaped \"logistic\" function, from 0 to 1, of the number " { $snippet "x" } "." } ; { $description "Outputs the sigmoid, an S-shaped \"logistic\" function, from 0 to 1, of the number " { $snippet "x" } "." } ;
HELP: signum
{ $values { "x" number } { "y" number } }
{ $description "Calculates the signum value. For a real number, " { $snippet "x" } ", this is its sign (-1, 0, or 1). For a complex number, " { $snippet "x" } ", this is the point on the unit circle of the complex plane that is nearest to " { $snippet "x" } "." } ;

6
basis/math/functions/functions-tests.factor
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@ -242,3 +242,9 @@ CONSTANT: log10-factorial-1000 0x1.40f3593ed6f8ep11
{ t } [ 3 15 roots [ 15 ^ 3 .01 ~ ] all? ] unit-test { t } [ 3 15 roots [ 15 ^ 3 .01 ~ ] all? ] unit-test
{ .5 } [ 0 sigmoid ] unit-test { .5 } [ 0 sigmoid ] unit-test
{ 1 } [ 12 signum ] unit-test
{ -1 } [ -5.0 signum ] unit-test
{ 0 } [ 0 signum ] unit-test
{ t } [ C{ 3.0 -1.5 } signum C{ 0.8944271909999157 -0.4472135954999579 } 1e-10 ~ ] unit-test

6
basis/math/functions/functions.factor
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@ -364,3 +364,9 @@ M: real atan >float atan ; inline
[ iota [ ^ * ] with with map ] tri ; [ iota [ ^ * ] with with map ] tri ;
: sigmoid ( x -- y ) neg e^ 1 + recip ; inline : sigmoid ( x -- y ) neg e^ 1 + recip ; inline
GENERIC: signum ( x -- y )
M: real signum sgn ;
M: complex signum dup abs / ;