--- OLD/ppm/ppmdist.c	Thu Jan  1 00:00:00 1970
+++ NEW/ppm/ppmdist.c	Thu Jan  1 00:00:00 1970
@@ -24,8 +24,8 @@
 
 int main ARGS((int argc, char *argv[]));
 gray newGrayValue ARGS((pixel * pix, struct colorToGrayEntry * colorToGrayMap, int colors));
-int cmpColorToGrayEntryByIntensity ARGS((void *entry1, void *entry2));
-int cmpColorToGrayEntryByFrequency ARGS((void *entry1, void *entry2));
+int cmpColorToGrayEntryByIntensity ARGS((const void *entry1, const void *entry2));
+int cmpColorToGrayEntryByFrequency ARGS((const void *entry1, const void *entry2));
 
 
 int
@@ -159,18 +159,14 @@
     pm_error("This should never happen - contact the maintainer");
 }
 
-int
-cmpColorToGrayEntryByIntensity(entry1, entry2)
-    void *entry1, *entry2;
+int cmpColorToGrayEntryByIntensity(const void *entry1, const void *entry2)
 {
-    return ((struct colorToGrayEntry *) entry1)->gray -
-	((struct colorToGrayEntry *) entry2)->gray;
+    return ((const struct colorToGrayEntry *) entry1)->gray -
+	((const struct colorToGrayEntry *) entry2)->gray;
 }
 
-int
-cmpColorToGrayEntryByFrequency(entry1, entry2)
-    void *entry1, *entry2;
+int cmpColorToGrayEntryByFrequency(const void *entry1, const void *entry2)
 {
-    return ((struct colorToGrayEntry *) entry1)->frequency -
-	((struct colorToGrayEntry *) entry2)->frequency;
+    return ((const struct colorToGrayEntry *) entry1)->frequency -
+	((const struct colorToGrayEntry *) entry2)->frequency;
 }