transitive_closure_1.pl : Transitive Closure Computes the transitive closure path for a binary relation edge, e.g. all the paths along the edges of a graph. Terminates only under refined semantics.
How to use: For a relation containing the pairs (A1,B1), .., (An,Bn), you enter edge(A1,B1), .., edge(An,Bn), and get the pairs (C1,D1), .., (Cm,Dm) of its transitive closure path(C1,D1), .., path(Cm,Dm).
See also: Thom Fruehwirth. Rule-Based Programming with CHR. 2006.
Program: Change the code, then submit! /* transitive_closure_1.pl: Transitive Closure (C) Thom.Fruehwirth at uni-ulm.de This program is distributed under the terms of the GNU General Public License: http://www.gnu.org/licenses/gpl.html %% DESCRIPTION Computes the transitive closure *path* for a binary relation *edge*, e.g. all the paths along the edges of a graph. # Terminates only under refined semantics. %% HOW TO USE For a relation containing the pairs (A1,B1), .., (An,Bn), you enter *edge(A1,B1), .., edge(An,Bn)*, # and get the pairs (C1,D1), .., (Cm,Dm) of its transitive closure *path(C1,D1), .., path(Cm,Dm)*. %% SEE ALSO Thom Fruehwirth. Rule-Based Programming with CHR. 2006. %% SAMPLE QUERIES Q: edge(1,2), edge(2,3), edge(2,4). A: edge(1,2), path(1,2), edge(2,3), path(2,3), path(1,3), edge(2,4), path(2,4), path(1,4). Q: edge(1,2), edge(2,3), edge(1,3). A: edge(1,2), path(1,2), edge(2,3), path(2,3), path(1,3), edge(1,3). Q: edge(1,2), edge(2,3), edge(3,1). A: edge(1,2), path(1,2), edge(2,3), path(2,3), path(1,3), edge(3,1), path(3,1), path(2,1), path(1,1), path(3,3), path(3,2), path(2,2). */ :- module(transitive_closure_1, [edge/2, path/2]). :- use_module(library(chr)). %% Deprecated syntax used for SICStus 3.x %handler tc1. %constraints edge/2, path/2. %% Syntax for SWI / SICStus 4.x :- chr_constraint edge/2, path/2. rem_dup @ path(X,Y) \ path(X,Y) <=> true. path_1 @ edge(X,Y) ==> path(X,Y). path_add @ edge(X,Y), path(Y,Z) ==> X\==Y, Y\==Z | path(X,Z).
Console: Enter query or select example from below, then submit and wait for answer! % loading graph/transitive_closure_1.pl | ?- consult(...). yes [0.226 seconds] | ?-