%Len vs. %Size in %Replace

["M. Lazarus" <mlazarus@xxxxxxxx>]

 Why doesn't %Replace() accept the %Size BIF in the 4th parm?

 This won't compile - it receives "RNF0384 The fourth parameter for 
%REPLACE is not valid."

ObjectName      10A
String  80A

C       EVAL String = %Replace( ObjectName :
                        String :
                        %Scan( 'qqqqqqqqqq': String ) :
                        %Size( ObjectName ) )

 This does compile:

C       EVAL String = %Replace( ObjectName :
                        String :
                        %Scan( 'qqqqqqqqqq': String ) :
                         %Len( ObjectName ) )

 -mark