36 lines
2.1 KiB
Factor
36 lines
2.1 KiB
Factor
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IN: graphs
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USING: help.markup help.syntax kernel assocs hashtables ;
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ARTICLE: "graphs" "Directed graph utilities"
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"Words for treating associative mappings as directed graphs can be found in the " { $vocab-link "graphs" } " vocabulary. A directed graph is represented as an assoc mapping each vertex to a set of edges entering that vertex, where the set is itself an assoc, with equal keys and values."
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$nl
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"To create a new graph, just create an assoc, for example by calling " { $link <hashtable> } ". To add vertices and edges to a graph:"
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{ $subsection add-vertex }
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"To remove vertices from the graph:"
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{ $subsection remove-vertex }
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"Since graphs are represented as assocs, they can be cleared out by calling " { $link clear-assoc } "."
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$nl
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"You can perform queries on the graph:"
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{ $subsection closure }
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"Directed graphs are used to maintain cross-referencing information for " { $link "definitions" } "." ;
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ABOUT: "graphs"
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HELP: graph
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{ $var-description "Temporary variable used by various graph words." } ;
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HELP: add-vertex
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{ $values { "vertex" object } { "edges" "a sequence" } { "graph" "an assoc mapping vertices to sequences of edges" } }
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{ $description "Adds a vertex to a directed graph, using the " { $snippet "edges" } " quotation to generate a sequence of edges leaving the vertex." }
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{ $side-effects "graph" } ;
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HELP: remove-vertex
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{ $values { "vertex" object } { "edges" "a sequence" } { "graph" "an assoc mapping vertices to sequences of edges" } }
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{ $description "Removes a vertex from a graph, using the quotation to generate a sequence of edges leaving the vertex." }
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{ $notes "The " { $snippet "edges" } " sequence must equal the value passed to " { $link add-vertex } ", otherwise some vertices of the graph may continue to refer to the removed vertex." }
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{ $side-effects "graph" } ;
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HELP: closure
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{ $values { "obj" object } { "quot" "a a quotation with stack effect " { $snippet "( obj -- assoc )" } } { "assoc" "a new assoc" } }
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{ $description "Outputs a set of all vertices reachable from " { $snippet "vertex" } " via edges given by the quotation. The set always includes " { $snippet "vertex" } "." } ;
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