--- a/IEEEFloat.st	Sun Dec 08 04:10:28 2019 +0100
+++ b/IEEEFloat.st	Sun Dec 08 21:07:40 2019 +0100
@@ -189,6 +189,10 @@
 
 !IEEEFloat class methodsFor:'constants'!
 
+pi
+    ^ Float pi
+!
+
 unity
     ^ 1.0
 !
@@ -874,6 +878,52 @@
 
 !IEEEFloat methodsFor:'mathematical functions'!
 
+ln
+    "return the natural logarithm of myself.
+     Raises an exception, if the receiver is less or equal to zero.
+
+     Not sure if this is really faster than using a taylor right away:
+     the three exp-computations at the end are done in qDouble and are tailors themself..."
+
+    |x|
+
+    self = self class zero ifFalse:[
+        self positive ifTrue:[
+            "/ initial approx.
+            x := self coerce:(self asFloat ln).
+            "/ three more iterations of newton...
+            x := x + (self * (x negated exp)) - 1.0.
+            x := x + (self * (x negated exp)) - 1.0.
+            x := x + (self * (x negated exp)) - 1.0.
+
+            ^ x
+        ].
+    ].
+
+    "/ now done via trapInfinity; was:
+    "/ d0 = 0.0 ifTrue:[
+    "/     ^ Infinity negative
+    "/ ].
+
+    "/ if you need -INF for a zero receiver, try Number trapInfinity:[...]
+    ^ self class
+        raise:(self = 0 ifTrue:[#infiniteResultSignal] ifFalse:[#domainErrorSignal])
+        receiver:self
+        selector:#ln
+        arguments:#()
+        errorString:'bad receiver in ln (not strictly positive)'
+
+    "                                 
+     Number trapInfinity:[ 0.0 ln ]   
+     Number trapInfinity:[ 0.0 asIEEEFloat ln ]    
+     1.0 asIEEEFloat ln         
+
+     2.7 asIEEEFloat ln
+     100 asIEEEFloat ln
+     3.0 asIEEEFloat ln printfPrintString:'%10.8f'
+    "
+!
+
 log10
     "return log base-10 of the receiver.
      Raises an exception, if the receiver is less or equal to zero.