1 ! Copyright (C) 2009 Jason W. Merrill.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: accessors arrays assocs combinators.smart compiler.units
4 effects generalizations help help.markup kernel make math
5 sequences vocabs words ;
9 TUPLE: dual ordinary-part epsilon-part ;
13 ! Ordinary numbers implement the dual protocol by returning
14 ! themselves as the ordinary part, and 0 as the epsilon part.
15 M: number ordinary-part>> ;
17 M: number epsilon-part>> drop 0 ;
19 : unpack-dual ( dual -- ordinary-part epsilon-part )
20 [ ordinary-part>> ] [ epsilon-part>> ] bi ;
24 : input-length ( word -- n ) stack-effect in>> length ;
26 MACRO: ordinary-op ( word -- o )
28 '[ [ ordinary-part>> ] _ napply _ execute ] ;
30 ! Takes N dual numbers <o1,e1> <o2,e2> ... <oN,eN> and weaves
31 ! their ordinary and epsilon parts to produce
32 ! e1 o1 o2 ... oN e2 o1 o2 ... oN ... eN o1 o2 ... oN
33 ! This allows a set of partial derivatives each to be evaluated
35 MACRO: duals>nweave ( n -- quot )
38 [ [ epsilon-part>> ] _ napply ] _ nkeep
39 [ ordinary-part>> ] _ napply _ nweave
42 MACRO: chain-rule ( word -- e )
43 [ input-length '[ _ duals>nweave ] ]
44 [ "derivative" word-prop ]
45 [ input-length 1 + '[ _ nspread ] ]
47 '[ [ @ _ @ ] sum-outputs ] ;
49 : set-dual-help ( dword word -- )
52 stack-effect [ in>> ] [ out>> ] bi append
53 [ dual ] { } map>assoc { $values } prepend
56 { $description } % "Version of " ,
57 { $link } swap suffix ,
58 " extended to work on dual numbers." ,
61 ] keepd set-word-help ;
65 MACRO: dual-op ( word -- quot )
66 [ '[ _ ordinary-op ] ]
67 [ input-length '[ _ nkeep ] ]
72 : define-dual ( word -- )
73 [ name>> "d" prepend "math.dual" create-word ] keep
74 [ stack-effect set-stack-effect ]
76 [ '[ _ dual-op ] define ]
79 ! Specialize math functions to operate on dual numbers.
80 [ all-words [ "derivative" word-prop ] filter
81 [ define-dual ] each ] with-compilation-unit