chickadee » srfi-135 » textual-map

It is an error if proc does not accept as many arguments as the number of textual arguments passed to textual-map, does not accept characters as arguments, or returns a value that is not a character, string, or text.

The textual-map procedure applies proc element-wise to the characters of the textual arguments, converts each value returned by proc to a text, and returns the concatenation of those texts. If more than one textual argument is given and not all have the same length, then textual-map terminates when the shortest textual argument runs out. The dynamic order in which proc is called on the characters of the textual arguments is unspecified, as is the dynamic order in which the coercions are performed. If any strings returned by proc are mutated after they have been returned and before the call to textual-map has returned, then textual-map returns a text with unspecified contents; the textual-map procedure itself does not mutate those strings.

Example:

(textual-map (lambda (c0 c1 c2)
               (case c0
                 ((#\1) c1)
                 ((#\2) (string c2))
                 ((#\-) (text #\- c1))))
             (string->text "1222-1111-2222")
             (string->text "Hi There!")
             (string->text "Dear John"))
  ⇒ «Hear-here!»