167 lines
6.4 KiB
Factor
167 lines
6.4 KiB
Factor
! Copyright (C) 2006 Chris Double.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel help.markup help.syntax arrays sequences math quotations ;
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IN: lists
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ABOUT: "lists"
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ARTICLE: "lists" "Lists"
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"The " { $vocab-link "lists" } " vocabulary implements linked lists. There are simple strict linked lists, but a generic list protocol allows the implementation of lazy lists as well."
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{ $subsection { "lists" "protocol" } }
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{ $subsection { "lists" "strict" } }
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{ $subsection { "lists" "manipulation" } }
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{ $subsection { "lists" "combinators" } }
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{ $vocab-subsection "Lazy lists" "lists.lazy" } ;
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ARTICLE: { "lists" "protocol" } "The list protocol"
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"Lists are instances of a mixin class:"
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{ $subsection list }
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"Instances of the mixin must implement the following words:"
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{ $subsection car }
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{ $subsection cdr }
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{ $subsection nil? } ;
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ARTICLE: { "lists" "strict" } "Constructing strict lists"
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"Strict lists are simply cons cells where the car and cdr have already been evaluated. These are the lists of Lisp. To construct a strict list, the following words are provided:"
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{ $subsection cons }
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{ $subsection swons }
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{ $subsection sequence>list }
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{ $subsection 1list }
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{ $subsection 2list }
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{ $subsection 3list } ;
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ARTICLE: { "lists" "combinators" } "Combinators for lists"
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"Several combinators exist for list traversal."
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{ $subsection leach }
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{ $subsection lmap }
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{ $subsection foldl }
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{ $subsection foldr }
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{ $subsection lmap>array }
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{ $subsection traverse } ;
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ARTICLE: { "lists" "manipulation" } "Manipulating lists"
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"To get at the contents of a list:"
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{ $subsection uncons }
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{ $subsection unswons }
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{ $subsection lnth }
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{ $subsection cadr }
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{ $subsection llength }
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"To get a new list from an old one:"
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{ $subsection lreverse }
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{ $subsection lappend }
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{ $subsection lcut } ;
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HELP: cons
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{ $values { "car" "the head of the list cell" } { "cdr" "the tail of the list cell" } { "cons" list } }
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{ $description "Constructs a cons cell." } ;
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HELP: swons
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{ $values { "cdr" "the tail of the list cell" } { "car" "the head of the list cell" } { "cons" list } }
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{ $description "Constructs a cons cell." } ;
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{ cons swons uncons unswons } related-words
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HELP: car
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{ $values { "cons" list } { "car" "the first item in the list" } }
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{ $description "Returns the first item in the list." } ;
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HELP: cdr
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{ $values { "cons" list } { "cdr" list } }
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{ $description "Returns the tail of the list." } ;
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{ car cdr } related-words
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HELP: nil
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{ $values { "symbol" "The empty cons (+nil+)" } }
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{ $description "Returns a symbol representing the empty list" } ;
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HELP: nil?
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{ $values { "object" object } { "?" "a boolean" } }
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{ $description "Return true if the cons object is the nil cons." } ;
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{ nil nil? } related-words
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{ 1list 2list 3list } related-words
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HELP: 1list
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{ $values { "obj" "an object" } { "cons" list } }
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{ $description "Create a list with 1 element." } ;
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HELP: 2list
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{ $values { "a" "an object" } { "b" "an object" } { "cons" list } }
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{ $description "Create a list with 2 elements." } ;
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HELP: 3list
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{ $values { "a" "an object" } { "b" "an object" } { "c" "an object" } { "cons" list } }
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{ $description "Create a list with 3 elements." } ;
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HELP: lnth
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{ $values { "n" "an integer index" } { "list" list } { "elt" "the element at the nth index" } }
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{ $description "Outputs the nth element of the list." }
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{ $see-also llength cons car cdr } ;
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HELP: llength
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{ $values { "list" list } { "n" "a non-negative integer" } }
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{ $description "Outputs the length of the list. This should not be called on an infinite list." }
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{ $see-also lnth cons car cdr } ;
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HELP: uncons
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{ $values { "cons" list } { "car" "the head of the list" } { "cdr" "the tail of the list" } }
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{ $description "Put the head and tail of the list on the stack." } ;
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HELP: unswons
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{ $values { "cons" list } { "car" "the head of the list" } { "cdr" "the tail of the list" } }
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{ $description "Put the head and tail of the list on the stack." } ;
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{ leach foldl lmap>array } related-words
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HELP: leach
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{ $values { "list" list } { "quot" { $quotation "( obj -- )" } } }
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{ $description "Call the quotation for each item in the list." } ;
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HELP: foldl
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{ $values { "list" list } { "identity" "an object" } { "quot" { $quotation "( prev elt -- next )" } } { "result" "the final result" } }
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{ $description "Combines successive elements of the list (in a left-assocative order) using a binary operation and outputs the final result." } ;
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HELP: foldr
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{ $values { "list" list } { "identity" "an object" } { "quot" { $quotation "( prev elt -- next )" } } { "result" "the final result" } }
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{ $description "Combines successive elements of the list (in a right-assocative order) using a binary operation, and outputs the final result." } ;
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HELP: lmap
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{ $values { "list" list } { "quot" { $quotation "( old -- new )" } } { "result" "the final result" } }
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{ $description "Applies the quotation to each element of the list in order, collecting the new elements into a new list." } ;
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HELP: lreverse
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{ $values { "list" list } { "newlist" list } }
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{ $description "Reverses the input list, outputing a new, reversed list. The output is a strict cons list." } ;
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HELP: list>array
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{ $values { "list" list } { "array" array } }
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{ $description "Convert a list into an array." } ;
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HELP: traverse
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{ $values { "list" list } { "pred" { $quotation "( list/elt -- ? )" } }
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{ "quot" { $quotation "( list/elt -- result)" } } { "result" "a new cons object" } }
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{ $description "Recursively traverses the list object, replacing any elements (which can themselves be sublists) that pred"
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" returns true for with the result of applying quot to." } ;
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HELP: list
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{ $class-description "The class of lists. All lists are expected to conform to " { $link { "lists" "protocol" } } "." } ;
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HELP: cadr
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{ $values { "list" list } { "elt" object } }
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{ $description "Returns the second element of the list, ie the car of the cdr." } ;
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HELP: lappend
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{ $values { "list1" list } { "list2" list } { "newlist" list } }
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{ $description "Appends the two lists to form a new list. The first list must be finite. The result is a strict cons cell, and the first list is exausted." } ;
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HELP: lcut
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{ $values { "list" list } { "index" integer } { "before" cons } { "after" cons } }
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{ $description "Analogous to " { $link cut } ", this word cuts a list into two pieces at the given index." } ;
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HELP: lmap>array
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{ $values { "list" list } { "quot" quotation } { "array" array } }
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{ $description "Executes the quotation on each element of the list, collecting the results in an array." } ;
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