USING: help.markup help.syntax ;
IN: astar
-{ find-path <astar> considered } related-words
+HELP: astar
+{ $description "This tuple must be subclassed and its method " { $link cost } ", "
+ { $link heuristic } ", and " { $link neighbours } " must be implemented. "
+ "Alternatively, the " { $link <astar> } " word can be used to build a non-specialized version." } ;
+
+HELP: cost
+{ $values
+ { "from" "a node" }
+ { "to" "a node" }
+ { "astar" "an instance of a subclassed " { $link astar } " tuple" }
+ { "n" "a number" }
+}
+{ $description "Return the cost to go from " { $snippet "from" } " to " { $snippet "to" } ". "
+ { $snippet "to" } " is necessarily a neighbour of " { $snippet "from" } "."
+} ;
+
+HELP: heuristic
+{ $values
+ { "from" "a node" }
+ { "to" "a node" }
+ { "astar" "an instance of a subclassed " { $link astar } " tuple" }
+ { "n" "a number" }
+}
+{ $description "Return the estimated (undervalued) cost to go from " { $snippet "from" } " to " { $snippet "to" } ". "
+ { $snippet "from" } " and " { $snippet "to" } " are not necessarily neighbours."
+} ;
+
+HELP: neighbours
+{ $values
+ { "node" "a node" }
+ { "astar" "an instance of a subclassed " { $link astar } " tuple" }
+ { "seq" "a sequence of nodes" }
+}
+{ $description "Return the list of nodes reachable from " { $snippet "node" } "." } ;
HELP: <astar>
{ $values
{ $snippet "neighbours" } " one builds the list of neighbours. The "
{ $snippet "cost" } " and " { $snippet "heuristic" } " ones represent "
"respectively the cost for transitioning from a node to one of its neighbour, "
- "and the underestimated cost for going from a node to the target."
+ "and the underestimated cost for going from a node to the target. This solution "
+ "may not be as efficient as subclassing the " { $link astar } " tuple."
} ;
HELP: find-path
! 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 neighbours heuristic cost
- goal g origin in-open-set in-closed-set open-set ;
+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 -- )
- [ g>> at ] 2keep
- [ [ goal>> ] [ heuristic>> call( n1 n2 -- c ) ] bi + ] 2keep
+ [ astar>> g>> at ] 2keep
+ [ [ goal>> ] [ astar>> heuristic ] bi + ] 2keep
(add-to-open-set) ;
: ?add-to-open-set ( node astar -- )
- 2dup in-closed-set>> key? [ 2drop ] [ add-to-open-set ] if ;
+ 2dup astar>> in-closed-set>> key? [ 2drop ] [ add-to-open-set ] if ;
: move-to-closed-set ( node astar -- )
- [ in-closed-set>> conjoin ] [ in-open-set>> delete-at ] 2bi ;
+ [ astar>> in-closed-set>> conjoin ] [ 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 ] [ g>> set-at ] bi-curry bi-curry bi* ] [ ?add-to-open-set ] 2bi ;
+ [ [ origin>> set-at ] [ astar>> g>> set-at ] bi-curry bi-curry bi* ] [ ?add-to-open-set ] 2bi ;
: cost-through ( origin node astar -- cost )
- [ cost>> call( n1 n2 -- c ) ] [ nip g>> at ] 3bi + ;
+ [ astar>> cost ] [ nip astar>> g>> at ] 3bi + ;
: ?set-g ( origin node astar -- )
[ cost-through ] 3keep [ swap ] 2dip
- 3dup g>> at [ 1/0. ] unless* > [ 4drop ] [ set-g ] if ;
+ 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 [ neighbours>> call( node -- neighbours ) ] keep [ ?set-g ] curry with each ;
+ dupd [ astar>> neighbours ] keep [ ?set-g ] curry with each ;
: (find-path) ( astar -- path/f )
dup open-set>> heap-empty? [
: (init) ( from to astar -- )
swap >>goal
- H{ } clone >>g
+ H{ } clone over astar>> (>>g)
+ H{ } clone over astar>> (>>in-closed-set)
H{ } clone >>origin
H{ } clone >>in-open-set
- H{ } clone >>in-closed-set
<min-heap> >>open-set
- [ 0 ] 2dip [ (add-to-open-set) ] [ g>> set-at ] 3bi ;
+ [ 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 ) ;
PRIVATE>
: find-path ( start target astar -- path/f )
- [ (init) ] [ (find-path) ] bi ;
+ (astar) new [ (>>astar) ] keep [ (init) ] [ (find-path) ] bi ;
: <astar> ( neighbours cost heuristic -- astar )
- astar new swap >>heuristic swap >>cost swap >>neighbours ;
+ astar-simple new swap >>heuristic swap >>cost swap >>neighbours ;
: considered ( astar -- considered )
in-closed-set>> keys ;