--- a/ShortFloat.st	Mon Jul 03 15:18:59 2017 +0200
+++ b/ShortFloat.st	Mon Jul 03 15:22:07 2017 +0200
@@ -1285,6 +1285,66 @@
     "
 !
 
+ln
+    "return the natural logarithm of the receiver.
+     Raises an exception, if the receiver is less or equal to zero."
+
+%{  /* NOCONTEXT */
+#ifndef __SCHTEAM__
+    float val, rslt;
+    OBJ newFloat;
+
+    val = __shortFloatVal(self);
+
+    /* 
+     * to suppress the warnBox opened by win32 
+     * to avoid returning -INF from some unix math libs (__osx__)
+     */
+    if (val > 0.0) {
+        __threadErrno = 0;
+# ifdef NO_LOGF
+        {
+            double dRslt = log((double)val);
+            rslt = (float)dRslt;
+        }
+# else
+        rslt = logf(val);
+# endif
+        if (! isnanf(rslt))  /* Currently all our systems support isnan() */
+        {
+            if (__threadErrno == 0) {
+                __qMKSFLOAT(newFloat, rslt);
+                RETURN ( newFloat );
+            }
+        }
+    }
+#endif
+%}.
+    "
+     an invalid value for logarithm
+    "
+    ^ self class
+        raise:#domainErrorSignal
+        receiver:self
+        selector:#ln
+        arguments:#()
+        errorString:'bad receiver in log10 (not strictly positive)'
+
+    "
+     10 asFloat ln       2.30258509299405
+     10 asShortFloat ln  2.302585
+     10 asLongFloat ln   2.302585092994045684
+     10 asQDouble ln     2.30258509299404568402
+
+     50 asFloat ln       3.91202300542815
+     50 asShortFloat ln  3.912023
+     50 asLongFloat ln   3.912023005428146059
+     50 asQDouble ln     3.91202300542814605862
+    "
+
+    "Created: / 03-07-2017 / 15:20:07 / cg"
+!
+
 log10
     "return the base-10 logarithm of the receiver.
      Raises an exception, if the receiver is less or equal to zero."