Function Ln (X : real) : Real;
Ln returns the natural logarithm of the real parameter X. X must be positive.
An run-time error will occur when X is negative.
Program Example37;
{ Program to demonstrate the Ln function. }
begin
Writeln (Ln(1)); { Prints 0 }
Writeln (Ln(Exp(1))); { Prints 1 }
end.