Add proper replace

- replace was actually replace-char
- backported string-replace-substring because it's only in Guile 3

1 files changed, 35 insertions, 2 deletions

diff --git a/Alpha/String.scm b/Alpha/String.scm
index 779c2fb..c7ad61f 100644
--- a/Alpha/String.scm
+++ b/Alpha/String.scm
@@ -1,12 +1,15 @@
 (define-module (Alpha String)
-  #:export (replace to-string str capitalize))
+  #:export (replace replace-char to-string str capitalize))
 
-(define (replace s match repl)
+(define (replace-char s match repl)
   (let ((f (lambda (a b)
              (let ((next-char (if (eq? a match) repl a)))
                (string-concatenate (list b (string next-char)))))))
     (string-fold f "" s)))
 
+(define (replace s match repl)
+  (string-replace-substring s match repl))
+
 (define (to-string x)
   (format #f "~a" x))
 
@@ -22,3 +25,33 @@
         (string-upcase s)
         (str (string-upcase (substring s 0 1))
              (substring s 1 )))))
+
+
+;;; {String Fun: string-replace-substring}
+;;;
+
+;; string-replace-substring By A. Wingo in
+;; https://lists.gnu.org/archive/html/guile-devel/2014-03/msg00058.html
+;; also in string-replace-substring guix:guix/utils.scm.
+
+(define (string-replace-substring str substring replacement)
+  "Return a new string where every instance of @var{substring} in string
+   @var{str} has been replaced by @var{replacement}. For example:
+
+   @lisp
+   (string-replace-substring \"a ring of strings\" \"ring\" \"rut\")
+   @result{} \"a rut of struts\"
+   @end lisp
+   "
+  (let ((sublen (string-length substring)))
+    (with-output-to-string
+      (lambda ()
+        (let lp ((start 0))
+          (cond
+           ((string-contains str substring start)
+            => (lambda (end)
+                 (display (substring/shared str start end))
+                 (display replacement)
+                 (lp (+ end sublen))))
+           (else
+            (display (substring/shared str start)))))))))