50 lines
2.5 KiB
Factor
50 lines
2.5 KiB
Factor
USING: arrays assocs help.markup help.syntax math.rectangles quadtrees quotations sequences ;
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IN: quadtrees
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ARTICLE: "quadtrees" "Quadtrees"
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"The " { $snippet "quadtrees" } " vocabulary implements the quadtree data structure in Factor."
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{ $subsections <quadtree> }
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"Quadtrees follow the " { $link "assocs-protocol" } " for insertion, deletion, and querying of exact points, using two-dimensional vectors as keys. Additional words are provided for spatial queries and pruning the tree structure:"
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{ $subsections
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in-rect
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prune-quadtree
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}
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"The following words are provided to help write quadtree algorithms:"
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{ $subsections
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descend
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each-quadrant
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map-quadrant
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}
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"Quadtrees can be used to \"swizzle\" a sequence to improve the locality of spatial data in memory:"
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{ $subsections swizzle } ;
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ABOUT: "quadtrees"
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HELP: <quadtree>
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{ $values { "bounds" rect } { "quadtree" quadtree } }
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{ $description "Constructs an empty quadtree covering the axis-aligned rectangle indicated by " { $snippet "bounds" } ". All the keys of " { $snippet "quadtree" } " must be two-dimensional vectors lying inside " { $snippet "bounds" } "." } ;
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HELP: prune-quadtree
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{ $values { "tree" quadtree } }
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{ $description "Removes empty nodes from " { $snippet "tree" } "." } ;
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HELP: in-rect
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{ $values { "tree" quadtree } { "rect" rect } { "values" sequence } }
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{ $description "Returns a " { $link sequence } " of values from " { $snippet "tree" } " whose keys lie inside " { $snippet "rect" } "." } ;
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HELP: descend
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{ $values { "pt" sequence } { "node" quadtree } { "subnode" quadtree } }
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{ $description "Descends into the subnode of quadtree node " { $snippet "node" } " that contains " { $snippet "pt" } ", leaving " { $snippet "pt" } " on the stack." } ;
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HELP: each-quadrant
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{ $values { "node" quadtree } { "quot" quotation } }
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{ $description "Calls " { $snippet "quot" } " with each subnode of " { $snippet "node" } " on the top of the stack in turn." } ;
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HELP: map-quadrant
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{ $values { "node" quadtree } { "quot" quotation } { "array" array } }
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{ $description "Calls " { $snippet "quot" } " with each subnode of " { $snippet "node" } " on the top of the stack in turn, collecting the four results into " { $snippet "array" } "." } ;
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HELP: swizzle
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{ $values { "sequence" sequence } { "quot" quotation } { "sequence'" sequence } }
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{ $description "Swizzles " { $snippet "sequence" } " based on the two-dimensional vector values returned by calling " { $snippet "quot" } " on each element of " { $snippet "sequence" } "." } ;
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