152 lines
6.6 KiB
Factor
152 lines
6.6 KiB
Factor
USING: help.markup help.syntax sequences strings ;
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IN: grouping
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ARTICLE: "grouping" "Groups and clumps"
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"Splitting a sequence into disjoint, fixed-length subsequences:"
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{ $subsections group }
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"A virtual sequence for splitting a sequence into disjoint, fixed-length subsequences:"
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{ $subsections groups <groups> <sliced-groups> }
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"Splitting a sequence into overlapping, fixed-length subsequences:"
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{ $subsections clump }
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"A virtual sequence for splitting a sequence into overlapping, fixed-length subsequences:"
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{ $subsections clumps <clumps> <sliced-clumps> }
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"The difference can be summarized as the following:"
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{ $list
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{ "With groups, the subsequences form the original sequence when concatenated:"
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{ $unchecked-example
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"USING: grouping ;"
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"{ 1 2 3 4 } dup" "2 <groups> concat sequence= ." "t"
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}
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}
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{ "With clumps, collecting the first element of each subsequence but the last one, together with the last subseqence, yields the original sequence:"
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{ $unchecked-example
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"USING: grouping ;"
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"{ 1 2 3 4 } dup" "2 <clumps> unclip-last [ [ first ] map ] dip append sequence= ." "t"
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}
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}
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}
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$nl
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"A combinator built using clumps:"
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{ $subsections monotonic? }
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"Testing how elements are related:"
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{ $subsections all-eq? all-equal? } ;
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ABOUT: "grouping"
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HELP: groups
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{ $class-description "Instances are virtual sequences whose elements are disjoint fixed-length subsequences of an underlying sequence. Groups are mutable and resizable if the underlying sequence is mutable and resizable, respectively."
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$nl
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"New groups are created by calling " { $link <groups> } " and " { $link <sliced-groups> } "." } ;
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HELP: group
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "array" "a sequence of sequences" } }
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{ $description "Splits the sequence into disjoint groups of " { $snippet "n" } " elements and collects the groups into a new array." }
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{ $notes "If the sequence length is not a multiple of " { $snippet "n" } ", the final subsequence in the list will be shorter than " { $snippet "n" } " elements." }
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{ $examples
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{ $example "USING: grouping prettyprint ;" "{ 3 1 3 3 7 } 2 group ." "{ { 3 1 } { 3 3 } { 7 } }" }
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} ;
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HELP: <groups>
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "groups" groups } }
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{ $description "Outputs a virtual sequence whose elements are disjoint subsequences of " { $snippet "n" } " elements from the underlying sequence." }
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{ $examples
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{ $example
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"USING: arrays kernel prettyprint sequences grouping ;"
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"9 >array 3 <groups> reverse! concat >array ." "{ 6 7 8 3 4 5 0 1 2 }"
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}
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{ $example
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"USING: kernel prettyprint sequences grouping ;"
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"{ 1 2 3 4 5 6 } 3 <groups> first ."
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"{ 1 2 3 }"
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}
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} ;
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HELP: <sliced-groups>
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "groups" groups } }
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{ $description "Outputs a virtual sequence whose elements are slices of disjoint subsequences of " { $snippet "n" } " elements from the underlying sequence." }
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{ $examples
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{ $example
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"USING: arrays kernel prettyprint sequences grouping ;"
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"9 >array 3 <sliced-groups>"
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"dup [ reverse! drop ] each concat >array ."
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"{ 2 1 0 5 4 3 8 7 6 }"
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}
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{ $example
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"USING: kernel prettyprint sequences grouping ;"
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"{ 1 2 3 4 5 6 } 3 <sliced-groups> second ."
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"T{ slice { from 3 } { to 6 } { seq { 1 2 3 4 5 6 } } }"
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}
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} ;
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HELP: clumps
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{ $class-description "Instances are virtual sequences whose elements are overlapping fixed-length subsequences o an underlying sequence. Clumps are mutable and resizable if the underlying sequence is mutable and resizable, respectively."
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$nl
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"New clumps are created by calling " { $link <clumps> } " and " { $link <sliced-clumps> } "." } ;
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HELP: clump
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "array" "a sequence of sequences" } }
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{ $description "Splits the sequence into overlapping clumps of " { $snippet "n" } " elements and collects the clumps into a new array." }
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{ $errors "Throws an error if " { $snippet "n" } " is smaller than the length of the sequence." }
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{ $examples
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{ $example "USING: grouping prettyprint ;" "{ 3 1 3 3 7 } 2 clump ." "{ { 3 1 } { 1 3 } { 3 3 } { 3 7 } }" }
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} ;
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HELP: <clumps>
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "clumps" clumps } }
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{ $description "Outputs a virtual sequence whose elements are overlapping subsequences of " { $snippet "n" } " elements from the underlying sequence." }
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{ $examples
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"Running averages:"
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{ $example
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"USING: grouping sequences math prettyprint kernel ;"
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"IN: scratchpad"
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"CONSTANT: share-price { 13/50 51/100 13/50 1/10 4/5 17/20 33/50 3/25 19/100 3/100 }"
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""
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"share-price 4 <clumps> [ [ sum ] [ length ] bi / ] map ."
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"{ 113/400 167/400 201/400 241/400 243/400 91/200 1/4 }"
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}
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{ $example
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"USING: kernel sequences grouping prettyprint ;"
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"{ 1 2 3 4 5 6 } 3 <clumps> second ."
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"{ 2 3 4 }"
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}
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} ;
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HELP: <sliced-clumps>
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{ $values { "seq" "a sequence" } { "n" "a non-negative integer" } { "clumps" clumps } }
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{ $description "Outputs a virtual sequence whose elements are overlapping slices of " { $snippet "n" } " elements from the underlying sequence." }
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{ $examples
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{ $example
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"USING: kernel sequences grouping prettyprint ;"
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"{ 1 2 3 4 5 6 } 3 <sliced-clumps> second ."
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"T{ slice { from 1 } { to 4 } { seq { 1 2 3 4 5 6 } } }"
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}
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} ;
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{ clumps groups } related-words
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{ clump group } related-words
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{ <clumps> <groups> } related-words
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{ <sliced-clumps> <sliced-groups> } related-words
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HELP: monotonic?
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{ $values { "seq" sequence } { "quot" { $quotation "( elt elt -- ? )" } } { "?" "a boolean" } }
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{ $description "Applies the relation to successive pairs of elements in the sequence, testing for a truth value. The relation should be a transitive relation, such as a total order or an equality relation." }
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{ $examples
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"Testing if a sequence is non-decreasing:"
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{ $example "USING: grouping math prettyprint ;" "{ 1 1 2 } [ <= ] monotonic? ." "t" }
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"Testing if a sequence is decreasing:"
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{ $example "USING: grouping math prettyprint ;" "{ 9 8 6 7 } [ < ] monotonic? ." "f" }
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} ;
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HELP: all-equal?
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{ $values { "seq" sequence } { "?" "a boolean" } }
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{ $description "Tests if all elements in the sequence are equal. Yields true with an empty sequence." } ;
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HELP: all-eq?
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{ $values { "seq" sequence } { "?" "a boolean" } }
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{ $description "Tests if all elements in the sequence are the same identical object. Yields true with an empty sequence." } ;
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{ monotonic? all-eq? all-equal? } related-words
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