98 lines
3.0 KiB
Factor
98 lines
3.0 KiB
Factor
! Copyright (C) 2010 Samuel Tardieu.
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: accessors assocs hash-sets heaps kernel math sequences sets shuffle ;
|
|
IN: path-finding
|
|
|
|
! This implements the A* algorithm. See http://en.wikipedia.org/wiki/A*
|
|
|
|
TUPLE: astar g in-closed-set ;
|
|
GENERIC: cost ( from to astar -- n )
|
|
GENERIC: heuristic ( from to astar -- n )
|
|
GENERIC: neighbours ( node astar -- seq )
|
|
|
|
<PRIVATE
|
|
|
|
TUPLE: (astar) astar goal origin in-open-set open-set ;
|
|
|
|
: (add-to-open-set) ( h node astar -- )
|
|
2dup in-open-set>> at* [ over open-set>> heap-delete ] [ drop ] if
|
|
[ swapd open-set>> heap-push* ] [ in-open-set>> set-at ] 2bi ;
|
|
|
|
: add-to-open-set ( node astar -- )
|
|
[ astar>> g>> at ] 2keep
|
|
[ [ goal>> ] [ astar>> heuristic ] bi + ] 2keep
|
|
(add-to-open-set) ;
|
|
|
|
: ?add-to-open-set ( node astar -- )
|
|
2dup astar>> in-closed-set>> in? [ 2drop ] [ add-to-open-set ] if ;
|
|
|
|
: move-to-closed-set ( node astar -- )
|
|
[ astar>> in-closed-set>> adjoin ] [ in-open-set>> delete-at ] 2bi ;
|
|
|
|
: get-first ( astar -- node )
|
|
[ open-set>> heap-pop drop dup ] [ move-to-closed-set ] bi ;
|
|
|
|
: set-g ( origin g node astar -- )
|
|
[ [ origin>> set-at ] [ astar>> g>> set-at ] bi-curry bi-curry bi* ] [ ?add-to-open-set ] 2bi ;
|
|
|
|
: cost-through ( origin node astar -- cost )
|
|
[ astar>> cost ] [ nip astar>> g>> at ] 3bi + ;
|
|
|
|
: ?set-g ( origin node astar -- )
|
|
[ cost-through ] 3keep [ swap ] 2dip
|
|
3dup astar>> g>> at [ 1/0. ] unless* >= [ 4drop ] [ set-g ] if ;
|
|
|
|
: build-path ( target astar -- path )
|
|
[ over ] [ over [ [ origin>> at ] keep ] dip ] produce 2nip reverse ;
|
|
|
|
: handle ( node astar -- )
|
|
dupd [ astar>> neighbours ] keep [ ?set-g ] curry with each ;
|
|
|
|
: (find-path) ( astar -- path/f )
|
|
dup open-set>> heap-empty? [
|
|
drop f
|
|
] [
|
|
[ get-first ] keep 2dup goal>> = [ build-path ] [ [ handle ] [ (find-path) ] bi ] if
|
|
] if ;
|
|
|
|
: (init) ( from to astar -- )
|
|
swap >>goal
|
|
H{ } clone over astar>> g<<
|
|
HS{ } clone over astar>> in-closed-set<<
|
|
H{ } clone >>origin
|
|
H{ } clone >>in-open-set
|
|
<min-heap> >>open-set
|
|
[ 0 ] 2dip [ (add-to-open-set) ] [ astar>> g>> set-at ] 3bi ;
|
|
|
|
TUPLE: astar-simple < astar cost heuristic neighbours ;
|
|
M: astar-simple cost cost>> call( n1 n2 -- c ) ;
|
|
M: astar-simple heuristic heuristic>> call( n1 n2 -- c ) ;
|
|
M: astar-simple neighbours neighbours>> call( n -- neighbours ) ;
|
|
|
|
TUPLE: bfs < astar neighbours ;
|
|
M: bfs cost 3drop 1 ;
|
|
M: bfs heuristic 3drop 0 ;
|
|
M: bfs neighbours neighbours>> at ;
|
|
|
|
TUPLE: dijkstra < astar costs ;
|
|
M: dijkstra cost costs>> swapd at at ;
|
|
M: dijkstra heuristic 3drop 0 ;
|
|
M: dijkstra neighbours costs>> at keys ;
|
|
|
|
PRIVATE>
|
|
|
|
: find-path ( start target astar -- path/f )
|
|
(astar) new [ astar<< ] keep [ (init) ] [ (find-path) ] bi ;
|
|
|
|
: <astar> ( neighbours cost heuristic -- astar )
|
|
astar-simple new swap >>heuristic swap >>cost swap >>neighbours ;
|
|
|
|
: considered ( astar -- considered )
|
|
in-closed-set>> members ;
|
|
|
|
: <bfs> ( neighbours -- astar )
|
|
[ bfs new ] dip >>neighbours ;
|
|
|
|
: <dijkstra> ( costs -- astar )
|
|
[ dijkstra new ] dip >>costs ;
|