Extend `regexp-replace*' to accept a start/end-position.

Note that this pushes the `ipre' argument to the end.

collects/racket/private/string.rkt

@@ -358,10 +358,8 @@
   ;; Like splitting, but insert a replacement between matches
   (define -regexp-replace*
     (let ([regexp-replace*
-           (lambda (pattern string orig-replacement [ipre #""])
+           (lambda (pattern string orig-replacement [start 0] [end #f] [ipre #""])
              (define-values [buf sub] (get-buf+sub string pattern))
-             (define start 0)
-             (define end #f)
              (define needs-string?
                (and (or (string? pattern) (regexp? pattern)) (string? string)))
              (define replacement
@@ -444,26 +442,30 @@
                   'regexp-replace*
                   "cannot replace a string with a byte string: "
                   replacement)))
+             (define r
+               (regexp-loop regexp-replace* loop start end pattern buf ipre
+                 ;; success-choose:
+                 (lambda (start ms acc)
+                   (list* (if (procedure? replacement)
+                            (check
+                             replacement
+                             (for/list ([m ms])
+                               (and m (sub buf (car m) (cdr m)))))
+                            (replac ms replacement))
+                          (sub buf start (caar ms))
+                          acc))
+                 ;; failure-k:
+                 (lambda (acc start end)
+                   (cons (if end (sub buf start end) (sub buf start)) acc))
+                 ;; port functions: use string case
+                 #f #f #f
+                 ;; flags
+                 #t #f))
              (apply
               (if (bytes? buf) bytes-append string-append)
-              (regexp-loop regexp-replace* loop start end pattern buf ipre
-                ;; success-choose:
-                (lambda (start ms acc)
-                  (list* (if (procedure? replacement)
-                           (check
-                            replacement
-                            (for/list ([m ms])
-                              (and m (sub buf (car m) (cdr m)))))
-                           (replac ms replacement))
-                         (sub buf start (caar ms))
-                         acc))
-                ;; failure-k:
-                (lambda (acc start end)
-                  (cons (if end (sub buf start end) (sub buf start)) acc))
-                ;; port functions: use string case
-                #f #f #f
-                ;; flags
-                #t #f)))])
+              (cond [(and (= start 0) (not end)) r]
+                    [(not end) (cons (sub string 0 start) r)]
+                    [else `(,(sub string 0 start) ,@r ,(sub string end))])))])
       regexp-replace*))
 
   ;; Returns all the matches for the pattern in the string, optionally

collects/scribblings/reference/regexps.scrbl

@@ -864,6 +864,8 @@ before the @litchar{\}. For example, the Racket constant
                           [insert (or/c string? bytes? 
                                         ((string?) () #:rest (listof string?) . ->* . string?)
                                         ((bytes?) () #:rest (listof bytes?) . ->* . bytes?))]
+                          [start-pos exact-nonnegative-integer? 0]
+                          [end-pos (or/c exact-nonnegative-integer? #f) #f]
                           [input-prefix bytes? #""])
          (or/c string? bytes?)]{
 
@@ -875,6 +877,10 @@ instead of just the first match. Only non-overlapping instances of
 recursively. Zero-length matches are treated the same as in
 @racket[regexp-match*].
 
+The optional @racket[start-pos] and @racket[end-pos] arguments select
+a portion of @racket[input] for matching; the default is the entire
+string or the stream up to an end-of-file.
+
 @examples[
 (regexp-replace* "([Mm])i ([a-zA-Z]*)" "mi cerveza Mi Mi Mi" 
                  "\\1y \\2")
@@ -882,6 +888,7 @@ recursively. Zero-length matches are treated the same as in
                  (lambda (all one two)
                    (string-append (string-downcase one) "y"
                                   (string-upcase two))))
+(regexp-replace* #px"\\w" "hello world" string-upcase 0 5)
 (display (regexp-replace* #rx"x" "12x4x6" "\\\\"))
 ]}
 

collects/tests/racket/basic.rktl

@@ -1111,6 +1111,11 @@
 
 (test "foofoo" regexp-replace* #px"(.)?" "a" (lambda args "foo"))
 
+(test "xxxxx world" regexp-replace* #px"\\w" "hello world" "x" 0 5)
+(test "HELLO world" regexp-replace* #px"\\w" "hello world" string-upcase 0 5)
+(test "hello world" regexp-replace* #px"o" "ohello world" "" 0 3)
+(test "hell world" regexp-replace* #px"o" "ohello world" "" 0 6)
+
 ;; Test weird port offsets:
 (define (test-weird-offset regexp-match regexp-match-positions)
   (test #f regexp-match "e" (open-input-string ""))
@@ -1312,7 +1317,7 @@
 (arity-test regexp-match-peek 2 6)
 (arity-test regexp-match-peek-positions 2 6)
 (arity-test regexp-replace 3 4)
-(arity-test regexp-replace* 3 4)
+(arity-test regexp-replace* 3 6)
 
 (test #t procedure? car)
 (test #f procedure? 'car)