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genequal
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Description
Compares obj1 and obj2 for equality using user-specified and built-in comparators.
Author
Requirements
None
Generalized equal? predicate
- generalized-equal? obj1 obj2 #!rest comparator-listprocedure
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.
- predicates->comparator type-predicate compare-predicateprocedure
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.
- numeric-comparator obj1 obj2 comparators-listprocedure
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.
- char-ci-comparator obj1 obj2 comparators-listprocedure
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.
- string-ci-comparator obj1 obj2 comparators-listprocedure
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
(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
License
BSD
Version history
Version 0.1
Initial release