1 ! Copyright (C) 2006 Chris Double.
2 ! See http://factorcode.org/license.txt for BSD license.
4 ! Based on pattern matching code from Paul Graham's book 'On Lisp'.
5 USING: assocs classes.tuple combinators kernel lexer macros make
6 math namespaces parser sequences words ;
11 : define-match-var ( name -- )
13 dup t "match-var" set-word-prop
14 dup [ get ] curry ( -- value ) define-declared ;
16 : define-match-vars ( seq -- )
17 [ define-match-var ] each ;
19 SYNTAX: MATCH-VARS: ! vars ...
20 ";" [ define-match-var ] each-token ;
22 : match-var? ( symbol -- bool )
23 dup word? [ "match-var" word-prop ] [ drop f ] if ;
25 : set-match-var ( value var -- ? )
26 building get ?at [ = ] [ ,, t ] if ;
28 : (match) ( value1 value2 -- matched? )
30 { [ dup match-var? ] [ set-match-var ] }
31 { [ over match-var? ] [ swap set-match-var ] }
32 { [ 2dup = ] [ 2drop t ] }
33 { [ 2dup [ _ eq? ] either? ] [ 2drop t ] }
34 { [ 2dup [ sequence? ] both? ] [
36 [ [ (match) ] 2all? ] [ 2drop f ] if ] }
37 { [ 2dup [ tuple? ] both? ]
38 [ [ tuple>array ] bi@ [ (match) ] 2all? ] }
42 : match ( value1 value2 -- bindings )
43 [ (match) ] H{ } make swap [ drop f ] unless ;
45 MACRO: match-cond ( assoc -- )
47 [ "Fall-through in match-cond" throw ]
50 [ [ dupd match ] curry ] dip
51 [ with-variables ] curry rot
55 : replace-patterns ( object -- result )
57 { [ dup number? ] [ ] }
58 { [ dup match-var? ] [ get ] }
59 { [ dup sequence? ] [ [ replace-patterns ] map ] }
60 { [ dup tuple? ] [ tuple>array replace-patterns >tuple ] }
64 : match-replace ( object pattern1 pattern2 -- result )
65 [ match [ "Pattern does not match" throw ] unless* ] dip swap
66 [ replace-patterns ] with-variables ;
68 : ?rest ( seq -- tailseq/f )
69 [ f ] [ rest ] if-empty ;
71 : (match-first) ( seq pattern-seq -- bindings leftover/f )
72 2dup shorter? [ 2drop f f ] [
73 2dup length head over match
74 [ swap ?rest ] [ [ rest ] dip (match-first) ] ?if
77 : match-first ( seq pattern-seq -- bindings )
80 : (match-all) ( seq pattern-seq -- )
81 [ nip ] [ (match-first) swap ] 2bi
82 [ , [ swap (match-all) ] [ drop ] if* ] [ 2drop ] if* ;
84 : match-all ( seq pattern-seq -- bindings-seq )
85 [ (match-all) ] { } make ;