136 lines
5.8 KiB
Factor
136 lines
5.8 KiB
Factor
! See http://factorcode.org/license.txt for BSD licence.
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USING: help.markup help.syntax ;
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IN: graph-theory
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ARTICLE: "graph-protocol" "Graph protocol"
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"All graphs must be instances of the graph mixin:"
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{ $subsection graph }
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"All graphs must implement a method on the following generic word:"
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{ $subsection vertices }
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"At least one of the following two generic words must have a method; the " { $link graph } " mixin has default definitions which are mutually recursive:"
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{ $subsection adjlist }
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{ $subsection adj? }
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"All mutable graphs must implement a method on the following generic word:"
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{ $subsection add-blank-vertex }
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"All mutable undirected graphs must implement a method on the following generic word:"
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{ $subsection add-edge }
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"Mutable directed graphs should not implement the above word, as it has a default definition defined in terms of the following generic word:"
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{ $subsection add-edge* }
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"The following two words have default definitions, but are available as generics to allow implementations to optimize them:"
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{ $subsection num-vertices }
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{ $subsection num-edges } ;
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HELP: graph
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{ $class-description "A mixin class whose instances are graphs. Custom implementations of the graph protocol should be declared as instances of this mixin for all graph functionality to work correctly:"
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{ $code "INSTANCE: hex-board graph" }
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} ;
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{ vertices num-vertices num-edges } related-words
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HELP: vertices
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{ $values { "graph" graph } { "seq" "The vertices" } }
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{ $description "Returns the vertices of the graph." } ;
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HELP: num-vertices
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{ $values { "graph" graph } { "n" "The number of vertices" } }
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{ $description "Returns the number of vertices in the graph." } ;
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HELP: num-edges
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{ $values { "graph" "A graph" } { "n" "The number of edges" } }
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{ $description "Returns the number of edges in the graph." } ;
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{ adjlist adj? } related-words
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HELP: adjlist
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{ $values
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{ "from" "The index of a vertex" }
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{ "graph" "The graph to be examined" }
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{ "seq" "The adjacency list" } }
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{ $description "Returns a sequence of vertices that this vertex links to" } ;
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HELP: adj?
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{ $values
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{ "from" "The index of a vertex" }
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{ "to" "The index of a vertex" }
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{ "graph" "A graph" }
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{ "?" "A boolean" } }
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{ $description "Returns a boolean describing whether there is an edge in the graph between from and to." } ;
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{ add-blank-vertex add-blank-vertices add-edge add-edge* } related-words
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HELP: add-blank-vertex
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{ $values
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{ "index" "A vertex index" }
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{ "graph" "A graph" } }
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{ $description "Adds a vertex to the graph." } ;
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HELP: add-blank-vertices
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{ $values
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{ "seq" "A sequence of vertex indices" }
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{ "graph" "A graph" } }
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{ $description "Adds vertices with indices in seq to the graph." } ;
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HELP: add-edge*
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{ $values
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{ "from" "The index of a vertex" }
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{ "to" "The index of another vertex" }
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{ "graph" "A graph" } }
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{ $description "Adds a one-way edge to the graph, between " { $snippet "from" } " and " { $snippet "to" } "."
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$nl
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"If you want to add a two-way edge, use " { $link add-edge } " instead." } ;
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HELP: add-edge
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{ $values
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{ "u" "The index of a vertex" }
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{ "v" "The index of another vertex" }
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{ "graph" "A graph" } }
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{ $description "Adds a two-way edge to the graph, between " { $snippet "u" } " and " { $snippet "v" } "."
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$nl
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"If you want to add a one-way edge, use " { $link add-edge* } " instead." } ;
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{ depth-first full-depth-first dag? topological-sort } related-words
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HELP: depth-first
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{ $values
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{ "v" "The vertex to start the search at" }
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{ "graph" "The graph to search" }
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{ "pre" "A quotation of the form ( n -- )" }
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{ "post" "A quotation of the form ( n -- )" }
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{ "?list" "A list of booleans describing the vertices visited in the search" }
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{ "?" "A boolean describing whether or not the end-search error was thrown" } }
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{ $description "Performs a depth-first search on " { $emphasis "graph" } ". The variable " { $emphasis "graph" } " can be accessed in both quotations."
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$nl
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"The " { $emphasis "pre" } " quotation is run before the recursive application of depth-first."
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$nl
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"The " { $emphasis "post" } " quotation is run after the recursive application of depth-first."
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$nl
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{ $emphasis "?list" } " is a list of booleans, " { $link t } " for every vertex visted during the search, and " { $link f } " for every vertex not visited." } ;
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HELP: full-depth-first
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{ $values
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{ "graph" "The graph to search" }
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{ "pre" "A quotation of the form ( n -- )" }
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{ "post" "A quotation of the form ( n -- )" }
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{ "tail" "A quotation of the form ( -- )" }
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{ "?" "A boolean describing whether or not the end-search error was thrown" } }
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{ $description "Performs a depth-first search on " { $emphasis "graph" } ". The variable " { $emphasis "graph" } "can be accessed in both quotations."
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$nl
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"The " { $emphasis "pre" } " quotation is run before the recursive application of depth-first."
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$nl
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"The " { $emphasis "post" } " quotation is run after the recursive application of depth-first."
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$nl
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"The " { $emphasis "tail" } " quotation is run after each time the depth-first search runs out of nodes. On an undirected graph this will be each connected subgroup but on a directed graph it can be more complex." } ;
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HELP: dag?
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{ $values
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{ "graph" graph }
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{ "?" "A boolean indicating if the graph is acyclic" } }
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{ $description "Using a depth-first search, determines if the specified directed graph is a directed acyclic graph. An undirected graph will produce a false result, as the algorithm does not eliminate cycles of length 2, which will include any edge that goes both ways." } ;
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HELP: topological-sort
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{ $values
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{ "graph" graph }
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{ "seq/f" "Either a sequence of values or f" } }
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{ $description "Using a depth-first search, topologically sorts the specified directed graph. Returns f if the graph contains any cycles, and a topologically sorted sequence otherwise." } ;
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