Although nonlcon is not specifically documented as having to return real values,
Nonlinear constraints, specified as a function handle or function name. nonlcon is a function that accepts a vector or array x and returns two arrays, c(x) and ceq(x).
- c(x) is the array of nonlinear inequality constraints at x. fmincon attempts to satisfyc(x) <= 0 for all entries of c.
- ceq(x) is the array of nonlinear equality constraints at x. fmincon attempts to satisfyceq(x) = 0 for all entries of ceq.
If c(x) were permitted to be complex, then c(x) <= 0 is not well defined. If c(x) were permitted to be complex, then is the implied definition real(c(x))<=0 or would it be real(c(x))<=0 & imag(c(x))<=0 -- leaving open the possibility that c(x) were (for example) -1-1i as satisfying constraints ?
