error: Function definition is misplaced or improperly nested error?

I am defining a nested function (bicomp1) inside a function (biaxialcomp) whose output is to be minimised using the fmincon optimization function, but I get an error that this function is misplaced or improperly nested. What could be the problem with it?

function [Mux, Muy] = biaxialcomp(c,app,gc,gs,bar,n,i)
th = [10 20 30 40 50 60 70 80];
Mux = zeros(1,8);
Muy = zeros(1,8);
for iv = 1:8
    % first potential scenario
    if app.b*tand(th(iv)) < app.t
        tt = app.b*sind(th(iv))+app.t*cosd(th(iv));
        c_opt = fmincon(@bicomp1,c,[],[],[],[],0,tt);
        function obj = bicomp1(c)
        a = 0.8*c;
        Xna = a/sind(th(iv));
        fcu = 0.67*app.Fcu/gc;
        ...
            

Answer 1

[Stephen23]

"What could be the problem with it?"

This:

    if ...
        ...
        function obj = bicomp1(c)

Function definitions cannot be nested inside control statements. To get the effect you are looking for, you will have to parameterize your function (i.e. either use a nested function or an anonymous function with the required parameters):

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[Abdelrahman Taha]

You're right. Thanks for your help.