string-ci<?

Conformance: R5RS Scheme

Purpose: Case-insensitively test whether a sequence of strings is in lexically ascending order.

Arguments:
X - string
Y... - strings

Implementation:

(define string-ci<?
  (letrec
    ((ci-lt?
       (lambda (x y)
         (cond ((null? x) (not (null? y)))
           ((null? y) #f)
           ((char-ci<? (car x) (car y)) #t)
           ((char-ci>? (car x) (car y)) #f)
           (else (ci-lt? (cdr x) (cdr y)))))))
  (predicate-iterator
    (lambda (x y)
      (ci-lt? (string->list x)
              (string->list y))))))

Example:

(string-ci<? "abc" "XYZ" "zZz") 
=> #t

See also:
string<?, string-ci=?, string-ci>?, string-ci<=?, string-ci>=?, char-ci<?, equal?.