The C-calculator mode math functions found in are very close to the corresponding functions found in the math library. Some other functions, not found in the math library, are also part of . Most of the numerically unstable functions (i.e. ln, log, exp,...) check for both an argument out of range and a value out of domain at each call. All math functions are double precision and can only be called from the C-calculator mode, or by using the let command from the fitting mode. These functions are also available in the conditional statements of the fitting mode if and while, since these statements are C-calculator mode statements, although part of fitting mode constructions.