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Article contents:== srfi-162 === Description srfi-162 is a set of procedures and comparators supplementing srfi-128. This extension provides srfi-162 modified for Chicken 6. Since srfi-162 contains the complete implementation of srfi-128, srfi-162 effectively replaces srfi-128. === Author * srfi-162 was authored by John Cowan * Modified for Chicken 6 by Jules Altfas === Repository * https://codeberg.org/jrapdx/srfi-162 === Requirements None. === srfi-162 API srfi-162 provides these procedures and pre-built comparators: <procedure>comparator-max comparator obj1 obj2 ...</procedure> * Applies the comparator procedure to given objects, returns the maximal object. Order of comparison is unspecified. <procedure>comparator-min comparator obj1 obj2 ...</procedure> * As above, except returns the minimal object. <procedure>comparator-max-in-list comparator list</procedure> <procedure>comparator-min-in-list comparator list</procedure> * As above except accepting a single list argument, returning max or min object in the given list. <record>default-comparator</record> * functions identically to a comparator generated by {{make-default-comparator}} from ''srfi-128''. <record>boolean-comparator</record> * #f compares before #t <record>real-comparator</record> * for real numbers, smaller numbers compare before larger numbers <record>char-comparator</record> * compares characters in Unicode codepoint order <record>char-ci-comparator</record> * case-insensitive comparison of characters <record>string-comparator</record> * compares strings using implementation's definition of {{string<?}} <record>string-ci-comparator</record> * case-insensitive comparison of strings using {{string-ci<?}} <record>pair-comparator</record> * compares pairs by applying {{make-pair-comparator}} to pairs with {{default-comparator}} for comparing {{car}} and {{cdr}} of the pairs <record>list-comparator</record> * comparator for lists using {{make-list-comparator}} with {{default-comparator}} to compare list elements <record>vector-comparator</record> * comparator for vectors using {{make-vector-comparator}} with {{default-comparator}} to compare vector elements <record>eq/eqv/equal-comparator</record> * These comparators behave in the same manner as respective calls to {{make-eq-comparator}}, {{make-eqv-comparator}}, {{make-equal-comparator}} === srfi-128 API <procedure>comparator? obj</procedure> * returns #t if ''obj'' is a comparator or #f if not <procedure>comparator-ordered? comparator</procedure> * returns #t if ''comparator'' has an ordering predicate, otherwise #f <procedure>comparator-hashable? comparator</procedure> * returns #t if ''comparator'' has a hash function, otherwise #f <procedure>make-comparator type-test equality ordering hash</procedure> * type-test: predicate that returns #t if argument is correct type, otherwise #f * equality: predicate returns #t if objects are the same, otherwise #f * ordering: predicate if first object precedes second object presented to the comparator. * hash: a procedure taking an object and returning an exact integer. <procedure>make-pair-comparator car-comparator cdr-comparator</procedure> * type-test returns #t if argument is a pair, #f otherwise. * equality predicate returns #t if cars are equal per ''car-comparator'' and cdrs are equal per ''cdr-comparator''. * ordering: cars are compared by ''car-comparator'', if not equal, cdrs are compared and if not equal, ordering predicate is applied. * hash function computes hash of car and cdr, and the hashes are hashed together. <procedure>make-list-comparator element-comparator type-test empty? head tail</procedure> * type-test returns #t when type-test is #t and list elements satisfy element-comparator. * an empty sequence (per empty?) compares less than non-empty. * if head elements are compared and if equal, tail elements are compared to determine order of input objects. * hash function of element-comparator computes hash of elements which are hashed together. <procedure>make-vector-comparator element-comparator type-test length ref</procedure> * type-test returns #t when type-test is #t and elements satisfy element-comparator. * equality-predicate is #t when lengths of vectors are equal, and elements are equal according to element-comparator. * ordering-predicate is #t when first vector length is less than second, or if equal, element-wise comparison is made. * hash function of element-comparator computes hash of elements when are hashed together. <procedure>make-default-comparator</procedure> * Comparing objects of disjoint types, all elements of one type compare less or greater than a second type. * The empty list is ordered before any pairs. * Comparing booleans, #f<#t. * Comparing characters must use char=? and char<?, order is Unicode codepoint order. * Comparing pairs must work the same as {{make-pair-comparator}}. * Comparing symbols uses an implementation-dependent total order. (Possibly applying {{symbol->string}} and {{string<?}}). * Comparing bytevectors, comparator should conform to {{make-vector-comparator (make-comparator exact-integer? = < number-hash) bytevector? bytevector-length bytevector-u8-ref}}. * Comparing complex numbers, real parts are compared first, and if equal, order is determined by comparing imaginary parts. * Real numbers are compared with = and <. * Comparing strings uses string=? and string<?. * Vector comparison should behave same as {{make-vector-comparator (make-default-comparator) vector? vector-length vector-ref}}. * For comparing types registered with {{comparator-register-default!}}, default comparator must work like the registered comparator. * Hashing is accomplished with {{default-hash}}. <procedure>default-hash obj</procedure> * Applied to a pair, this procedure must return result of hashing together results of hashing car and cdr of the pair. * Applied to boolean, character, string, symbol and number values, result must be the same as produced by boolean-hash, char-hash, string-hash, symbol-hash, or number-hash. * Applied to list or vector types, result is the result of hashing together the hash of each element. ==== Accessors <procedure>comparator-type-test-predicate comparator</procedure> <procedure>comparator-equality-predicate comparator</procedure> <procedure>comparator-ordering-predicate comparator</procedure> <procedure>comparator-hash-function comparator</procedure> * These procedures return the 4 procedures of the comparator. <procedure>comparator-test-type comparator obj</procedure> <procedure>comparator-check-type comparator obj</procedure> * These procedures invoke the comparator's type-test predicate on obj. The latter signals an error if not #t. Less efficient than {{comparator-type-test-predicate}} but more convenient. <procedure>comparator-hash comparator obj</procedure> * Invokes comparator's hash function on obj. ==== Comparison predicates <procedure>=? comparator object1 object2 object3 ...</procedure> <procedure><? comparator object1 object2 object3 ...</procedure> <procedure>>? comparator object1 object2 object3 ...</procedure> <procedure><=? comparator object1 object2 object3 ...</procedure> <procedure>>=? comparator object1 object2 object3 ...</procedure> * These procedures apply the equality and ordering predicates of comparator to objects. If all object comparisons return #t, result is #t, otherwise #f. <syntax>comparator-if<=> [ <comparator> ] <object1> <object2> <less-than> <equal-to> <greater-than></syntax> * If comparator ordering predicate returns #t, then {{<less-than>}} is evaluated. If the equality predicate is #t, then {{<equal-to>}} is evaluated, otherwise {{<greater-than>}} is evaluated and result returned. ==== Documentation For more information please confer the srfi documents: * [[https://srfi.schemers.org/srfi-162/srfi-162.html|srfi-162]] * [[https://srfi.schemers.org/srfi-128/srfi-128.html|srfi-128]] === Examples <enscript highlight="scheme"> (import srfi-162) (=? list-comparator '(a b c) '(a b c)) ;; -> #t (=? list-comparator '(a b c) '(a b c d)) ;; -> #f (=? list-comparator '(11 22 33) '(11 22 33)) ;; -> #t (=? list-comparator '(11 22 33) '(11 22 333)) ;; -> #f (=? list-comparator '(11 22 33) '(11 22 zz)) ;; -> #f (=? list-comparator '("abc" "cde") '("abc" "cde")) ;;-> #t (=? list-comparator '("abc" "cde") '("abc" "cdE")) ;;-> #f (>? list-comparator '("abc" "cde") '("abc" "cdE")) ;;-> #t ;; make comparator for case-insensitive comparisons of string lists (define list-ci-comparator (make-list-comparator string-ci-comparator list? null? car cdr)) (=? list-ci-comparator '("abc" "cde") '("abc" "cde")) ;; -> #t (=? list-ci-comparator '("abc" "cde") '("abC" "cdE")) ;; -> #t (<? list-ci-comparator '("abc" "cde") '("abC" "cdE")) ;; -> #f (>? list-ci-comparator '("abc" "cde") '("abC" "cdE")) ;; -> #f (=? list-ci-comparator '("abc" "cde") '("abC" "cdEf")) ;; -> #f </enscript> === Version * version 0.1 ''November 28, 2025'' === License * BSD Description of your changes:

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