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Article contents:== Outdated egg! This is an egg for CHICKEN 4, the unsupported old release. You're almost certainly looking for [[/eggref/5/list-utils|the CHICKEN 5 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-5.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags: egg]] == list-utils Miscellaneous list oriented routines. [[toc:]] == Documentation === skip+ <procedure>(skip+ LIST COUNT) -> (list integer)</procedure> Returns 2 values, the {{COUNT}} {{pair}} from {{LIST}}, and the remaining count. The remaining count will be zero when end-of-list reached. {{COUNT}} is a {{natural fixnum}}. <enscript language=scheme> (skip+ '(1 2) 3) ;=> '() 1 (skip+ '(1 2 3) 3) ;=> '() 0 (skip+ '(1 2 3 4) 3) ;=> '(4) 0 </enscript> === split-at+ <procedure>(split-at+ LIST COUNT [PADS]) -> (list list)</procedure> Returns 2 values, the leading {{COUNT}} elements from {{LIST}} as a new {{list}}, and the remaining elements from {{LIST}}. Should there be fewer than {{COUNT}} elements available padding is attempted. Padding is performed by trying to complete the remaining elements from the {{list}} {{PADS}}. {{COUNT}} is a {{natural fixnum}}. {{PADS}} is a {{list}} or {{#f}}. Default is {{'()}}. A negative {{COUNT}} is treated as {{0}}. When {{PADS}} is {{#f}} then an incomplete leading sublist is treated as {{'()}}. The very odd treatment of {{PADS}} = {{#f}} can safely be ignored since this is not the default behavior. <enscript language=scheme> (split-at+ '(1 2 3) 3) ;=> '(1 2 3) '() (split-at+ '(1 2 3) 2) ;=> '(1 2) '(3) (split-at+ '(1 2 3) 4) ;=> '(1 2 3) '() (split-at+ '(1 2 3) 4 #f) ;=> '() '() </enscript> === section <procedure>(section LIST SIZE [[STEP] PADS]) -> list</procedure> Returns a {{list}} of {{list}}, built by taking {{SIZE}} elements from {{LIST}} every {{STEP}} elements. When too few elements remain to complete a ''section'' padding is performed. {{SIZE}} is a {{positive fixnum}}. {{STEP}} is a {{positive fixnum}}. Default is {{SIZE}}. {{PADS}} is a {{list}} or {{#f}}. Default is {{'()}}. When {{PADS}} is {{#f}} then any incomplete trailing section is dropped. The very odd treatment of {{PADS}} = {{#f}} can safely be ignored since this is not the default behavior. <enscript language=scheme> (section '(1 2) 3 3 '(3 4 5)) ;=> ((1 2 3)) (section '(1 2 3) 2 1 '(3 4 5)) ;=> ((1 2) (2 3)) (section '(1 2 3) 2 2 '(4 5)) ;=> ((1 2) (3 4)) (section '(1 2 3) 2 2) ;=> ((1 2) (3)) </enscript> === length=0? <macro>(length=0? LIST) -> boolean</macro> List of length zero? (Just {{null?}}.) === length=1? <macro>(length=1? LIST) -> boolean</macro> List of length one? === length>1? <macro>(length>1? LIST) -> boolean</macro> List of length greater than one? === length=2? <macro>(length=2? LIST) -> boolean</macro> List of length two? === ensure-list <macro>(ensure-list OBJECT) -> list</macro> Returns a list, either the list {{OBJECT}} or {{(list OBJECT)}}. === not-null? <macro>(not-null? LIST) -> (or list boolean)</macro> Returns {{#f}} if the given {{LIST}} is empty, and {{LIST}} otherwise. === alist-delete-first <macro>(alist-delete-first KEY ALIST [TEST?])</macro> Returns {{(alist-delete-with-count KEY ALIST [TEST?] 1)}}. === alist-delete-first! <macro>(alist-delete-first! KEY ALIST [TEST?])</macro> Destructive version of {{alist-delete-first}}. === assoc-def <macro>(assoc-def KEY ALIST [TEST] [NOT-FOUND])</macro> The assoc procedure with an optional test and default value. Error signaling version of {{assoc}}. When the {{KEY}} is not found and a {{NOT-FOUND}} value is not supplied an {{error}} is invoked. === assv-def <macro>(assv-def KEY ALIST [NOT-FOUND])</macro> The assv procedure with a default value. Error signaling version of {{assv}}. When the {{KEY}} is not found and a {{NOT-FOUND}} value is not supplied an {{error}} is invoked. === assq-def <macro>(assq-def KEY ALIST [NOT-FOUND])</macro> The assq procedure with a default value. Error signaling version of {{assq}}. When the {{KEY}} is not found and a {{NOT-FOUND}} value is not supplied an {{error}} is invoked. === alist-inverse-ref <procedure>(alist-inverse-ref VALUE ALIST [TEST? [NOT-FOUND]])</procedure> Returns the first key associated with {{VALUE}} in the {{ALIST}} using the {{TEST?}} predicate, else {{NOT-FOUND}}. {{TEST?}} is {{eqv?}} and {{NOT-FOUND}} is {{#f}}. === alist-delete-duplicates <procedure>(alist-delete-duplicates KEY ALIST [TEST? [COUNT]]) -> alist</procedure> Deletes the first {{COUNT}} associations from alist {{ALIST}} with the given key {{KEY}}, using key-comparison procedure {{TEST?}}. The dynamic order in which the various applications of equality are made is from the alist head to the tail. Returns a new alist. The alist is not disordered - elements that appear in the result alist occur in the same order as they occur in the argument alist. The equality procedure is used to compare the element keys, {{key[i: 0 <= i < (length ALIST)}}', of the alist's entries to the key parameter in this way: {{(TEST? KEY key[i])}}. {{COUNT}} defaults to unlimited, & {{EQUALITY?}} defaults to {{eqv?}}. === alist-delete-duplicates! <procedure>(alist-delete-duplicates! KEY ALIST [TEST? [COUNT]]) -> alist</procedure> Destructive version of {{alist-delete-with-count}}. {{alist-delete-first}} and {{alist-delete-first!}} are also available. === unzip-alist <procedure>(unzip-alist ALIST)</procedure> Returns 2 values, a list of the keys & a list of the values from the {{ALIST}}. === zip-alist <procedure>(zip-alist KEYS VALUES)</procedure> Returns an association list with elements from the corresponding items of {{KEYS}} and {{VALUES}}. === plist->alist <procedure>(plist->alist PLIST) -> list</procedure> Returns the association-list form of {{PLIST}}. === alist->plist <procedure>(alist->plist ALIST) -> list</procedure> Returns the property-list form of {{ALIST}}. === shift! <procedure>(shift! LIST [DEFAULT]) -> *</procedure> Returns the first element of {{LIST}}, or {{DEFAULT}} when {{LIST}} is null. The {{car}} and {{cdr}} of the first {{pair}} of {{LIST}} are set to the corresponding element of the second {{pair}}. Like a stack-pop. === unshift! <procedure>(unshift! OBJECT LIST) -> list</procedure> The {{car}} of the first {{pair}} of {{LIST}} is set to {{OBJECT}}. The {{cdr}} of the first {{pair}} of {{LIST}} is set to {{LIST}}. Like a stack-push. === shift!/set <macro>(shift!/set VARIABLE [WHEN-EMPTY])</macro> Like {{shift!}} but assigns the {{VARIABLE}} {{'()}} after shifting from a list of length 1. {{WHEN-EMPTY}}, which defaults to {{#f}}, is returned when the list bound to {{VARIABLE}} is empty. === andmap <procedure>(andmap FUNC LIST...) -> boolean</procedure> The arity of the function {{FUNC}} must be the length of {{LIST...}}. {{(and (FUNC (car LIST)...) (andmap FUNC (cdr LIST)...))}}. === ormap <procedure>(ormap FUNC LIST...) -> boolean</procedure> The arity of the function {{FUNC}} must be the length of {{LIST...}}. {{(or (FUNC (car LIST)...) (ormap FUNC (cdr LIST)...))}}. === pair-ref <procedure>(pair-ref LIST IDX) -> list</procedure> Returns the {{IDX}}th {{pair}} of {{LIST}}. === list-set! <procedure>(list-set! LIST IDX OBJ) -> list</procedure> Replaces the {{car}} the {{(pair-ref LIST IDX)}} with {{OBJ}}. === list-copy* <procedure>(list-copy* LIST START END FILL) -> list</procedure> Returns a copy of {{LIST}}, from {{START}} until {{END}}, where {{END}} maybe {{>}} {{(length LIST))}}. In which case {{FILL}} is used. == Usage <enscript language=scheme> (require-extension list-utils) </enscript> == Requirements [[check-errors]] == Bugs and Limitations == Author [[/users/kon-lovett|Kon Lovett]] == Version history ; 1.4.0 : Add {{alist-delete-duplicates(!)}}, {{pair-ref}}, {{list-set!}}, {{list-copy*}}. Deperecate {{alist-delete-with/for-count(!)}}. ; 1.3.0 : Add {{alist-delete-with-count}} & {{alist-delete-with-count!}}. ; 1.2.0 : Add {{alist-delete-for-count}} & {{alist-delete-for-count!}}. ; 1.1.2 : . ; 1.1.1 : Fix for ticket #630 ; 1.1.0 : Added {{skip+}}, {{split-at+}}, and {{section}}. ; 1.0.0 : Hello, == License Copyright (C) 2010-2017 Kon Lovett. All rights reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 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