I now found out how to solve the problem. It works this way: :prog() :prgm :Inputstr f User inputs a function f as string :expr(f)-> h f is converted to expression h :disp h|x=a Calculates and displays h(a) :Endprgm I donīt know why it doesnīt work in another way. -- Sent through GMX FreeMail - http://www.gmx.net