[gimp] Bug 746467 - 'convert-decimal-to-base' produces erroneous results

[Michael Schumacher <schumaml src gnome org>]

commit 06bc22b1976508a5c9cf19a70aaff22d71b79b8d
Author: Saul Goode <saul crazyauntgail com>
Date:   Sat Aug 15 20:20:19 2015 +0200

    Bug 746467 - 'convert-decimal-to-base' produces erroneous results

 plug-ins/script-fu/scripts/palette-export.scm |   35 +++++++++---------------
 1 files changed, 13 insertions(+), 22 deletions(-)
---
diff --git a/plug-ins/script-fu/scripts/palette-export.scm b/plug-ins/script-fu/scripts/palette-export.scm
index 2d33ef7..12d89ba 100644
--- a/plug-ins/script-fu/scripts/palette-export.scm
+++ b/plug-ins/script-fu/scripts/palette-export.scm
@@ -18,28 +18,19 @@
 
 ; Converts a decimal number to another base. The returned number is a string
 (define (convert-decimal-to-base num base)
-  (define (highest-order num base)
-    (if (and (<= 0 num) (< num base))
-        0
-        (+ 1 (highest-order (quotient num base) base))
-        )
-    )
-  (define (calc base num str)
-    (let ((max-order (highest-order num base)))
-      (cond ((not (= 0 max-order))
-             (let ((num-of-times (quotient
-                                 num (inexact->exact (expt base max-order)))))
-               (calc base
-                     (- num (* num-of-times (expt base max-order)))
-                     (string-append str
-                                   (list-ref conversion-digits num-of-times)))
-               )
-             )
-            (else (string-append str (list-ref conversion-digits num)))
-            ))
-    )
-  (calc base num "")
-  )
+  (if (< num base) 
+    (list-ref conversion-digits num) 
+    (let loop ((val num)
+               (order (inexact->exact (truncate (/ (log num) 
+                                                   (log base)))))
+               (result ""))
+      (let* ((power (expt base order))
+             (digit (quotient val power)))
+        (if (zero? order)
+          (string-append result (list-ref conversion-digits digit)) 
+          (loop (- val (* digit power))
+                (pred order)
+                (string-append result (list-ref conversion-digits digit))))))))
 
 ; Convert a string representation of a number in some base, to a decimal number
 (define (convert-base-to-decimal base num-str)