Indicate a failed computation
This functionality does not run in MATLAB.
FAIL is a keyword of the MuPAD® language. Many functions of the library use the return value FAIL to indicate failed computations or non-existing elements.
FAIL is used as the return value for computations that failed. Also, requesting non-existing slots of domains or function environments yields FAIL. Due to this behavior, library functions can try computations without provoking errors.
A function should return FAIL or an error if at least one of its inputs is FAIL.
The following attempt to convert sqrt(3) to an integer of a residue class ring must fail:
poly(sqrt(3)*x, [x], Dom::IntegerMod(3))
The following matrix is not invertible. You can try to invert it without producing an error:
A := matrix([[1, 1], [1, 1]]): 1/A
Most functions return FAIL or an error on input of FAIL:
Error: An arithmetical expression is expected. [sin]
FAIL evaluates to itself:
FAIL, eval(FAIL), level(FAIL, 5)