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Article contents:== Outdated egg!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/genequal|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. == genequal [[toc:]] === Description Compares ''obj1'' and ''obj2'' for equality using user-specified and built-in comparators. === Author [[/users/john-cowan|John Cowan]] === Requirements None === Generalized {{equal?}} predicate <procedure>(generalized-equal? obj1 obj2 . comparator-list)</procedure> A ''comparator'' is a procedure that is given two arguments to compare. It returns {{#t}} if its arguments are to be considered equal, {{#f}} if they are to be considered unequal, and any other value if it cannot decide. The third argument passed to a comparator is a list of comparators to be used in recursive calls to {{generalized-equal?}}. First, each element of ''comparator-list'' is invoked on ''obj1'' and ''obj2'', passing ''comparator-list'' as its third argument. If the comparator returns {{#t}} or {{#f}}, that is the result. If all comparators in the list have been invoked without a {{#t}} or {{#f}} result, then {{generalized-equal?}} determines if both ''obj1'' and ''obj2'' are pairs, strings, vectors, u8vectors, hash tables with the same test function, or SRFI-99 records of the same type. (It cannot introspect on SRFI-9 or Chicken-native records.) If they are not, then {{generalized-equal?}} returns what {{eqv?}} returns on ''obj1'' and ''obj2''. Otherwise, if the containers have different numbers of elements, the result is {{#f}}. Otherwise, {{generalized-equal?}} invokes itself recursively on each corresponding element of the containers, passing itself the same comparators. If a recursive call returns {{#f}}, that is the result; if all recursive calls return {{#t}}, that is the result. <procedure>(predicates->comparator type-predicate compare-predicate)</procedure> Returns a comparator that invokes ''type-predicate'' on its first and its second arguments. If they both return {{#t}}, then they are assumed to be of the same type, and ''compare-predicate'' is invoked on the first and second arguments together. If the result is {{#t}} or {{#f}}, then the comparator returns {{#t}} or {{#f}} respectively. If they are not of the same type, a third value is returned. The comparator always ignores its third argument. === Comparators Specifying all three of these comparators causes {{generalized-equal?}} to act like Common Lisp's {{EQUALP}}. <procedure>(numeric-comparator obj1 obj2 comparators-list)</procedure> A comparator that returns {{#t}} if ''obj1'' and ''obj2'' are numbers that are equal by {{=}}, {{#f}} if they are not equal by {{=}}, and a third value otherwise. The ''comparators-list'' argument is ignored. <procedure>(char-ci-comparator obj1 obj2 comparators-list)</procedure> A comparator that returns {{#t}} if ''obj1'' and ''obj2'' are both characters that are equal by {{char-ci=?}}, {{#f}} if they are not equal by {{char-ci=?}}, and a third value otherwise. The ''comparators-list'' argument is ignored. <procedure>(string-ci-comparator obj1 obj2 comparators-list)</procedure> A comparator that returns {{#t}} if ''obj1'' and ''obj2'' are both strings that are equal by {{string-ci=?}}, {{#f}} if they are not equal by {{string-ci=?}}, and a third value otherwise. The ''comparators-list'' argument is ignored. === Examples <enscript highlight=scheme> (use genequal) (use srfi-99) (define-record-type foo (make-foo x) foo? (x foo-x foo-set-x!)) (define-record-type bar (make-bar x) bar? (x bar-x)) (define a (make-foo 10)) (define b (make-foo 10)) (define c (make-bar 10)) (generalized-equal? a b) => #t (generalized-equal? a c) => #f (foo-set-x! a 20) (generalized-equal? a b) => #f (generalized-equal? '("A" "B") '("a" "b")) => #f (generalized-equal? '("A" "B") '("a" "b") string-ci-comparator) => #t (generalized-equal? 2 2.0) => #f (generalized-equal? 2 2.0 numeric-comparator) => #t </enscript> === License BSD === Version history ==== Version 0.1 Initial release Description of your changes:

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