--- a/Number.st	Mon May 09 16:52:17 2016 +0200
+++ b/Number.st	Mon May 09 16:53:50 2016 +0200
@@ -1325,10 +1325,13 @@
 cbrt
     "return the cubic root of the receiver"
 
+    "/ if I am not a Float (or a less general lpReal),
+    "/ retry after converting to float
     (self isLimitedPrecisionReal not
     or:[self generality < 1.0 generality]) ifTrue:[
         ^ self asFloat cbrt.
     ].
+    "/ very slow fallback
     ^ self cbrt_withAccuracy:self epsilon
 !
 
@@ -1343,10 +1346,13 @@
 exp
     "compute e**x of the receiver"
 
+    "/ if I am not a Float (or a less general lpReal),
+    "/ retry after converting to float
     (self isLimitedPrecisionReal not
     or:[self generality < 1.0 generality]) ifTrue:[
         ^ self asFloat exp.
     ].
+    "/ very slow fallback
     ^ self exp_withAccuracy:self epsilon
 !
 
@@ -1368,10 +1374,13 @@
     "return the natural logarithm of myself.
      Raises an exception, if the receiver is less or equal to zero."
 
+    "/ if I am not a Float (or a less general lpReal),
+    "/ retry after converting to float
     (self isLimitedPrecisionReal not
     or:[self generality < 1.0 generality]) ifTrue:[
         ^ self asLongFloat ln.
     ].
+    "/ very slow fallback
     ^ self ln_withAccuracy:self epsilon
 
     "
@@ -1450,10 +1459,13 @@
 sqrt
     "return the square root of the receiver"
 
+    "/ if I am not a Float (or a less general lpReal),
+    "/ retry after converting to float
     (self isLimitedPrecisionReal not
     or:[self generality < 1.0 generality]) ifTrue:[
         ^ self asFloat sqrt.
     ].
+    "/ very slow fallback
     ^ self sqrt_withAccuracy:self epsilon
 !