Question

Is plhs[] preallocated to some size?

Specifically, if the user hasn’t provided any output args, can I still assign to plhs[0]? plhs[i], i>0?

Or should I check nlhs to see that there’s the appropriate amount of output args?

Answer 1

plhs has the size given ny nlhs. Except, if nlhs == 0, you may assign to plhs[0] in order to provide a value for ans – if you want so.

There are functions which differentiate between “targetless” calls and calls with assignment. E.g., a = path does other stuff than path, while sum([1 2 3]) does the same as a = sum([1 2 3]). This said distinction is the reason for that.