Decrements a number.
xis a variable containing a number
nis an integer
x is a variable that is currently containing a number (which includes integers, rational numbers, real numbers, and complex numbers), then
dec(x, n) decreases the value of
n; hence, its new value becomes
x − n. This value is also returned by the
dec function. If omitted,
n will be set to
x must be an lvalue of type number. It can be a variable or a subscript or member of an object container variable.