fmincon optimization with integral function

I'm trying to minimize the area of a function using fmincon and integral function My function is as given below

func = @(x)integral((@(l)(x(1)-l)),x(2),x(3),'ArrayValued',true);
...
[x, fval] = fmincon(func,x0,A,b,Aeq,beq,lb,ub,nonlcon);

The error I'm seeing is -

Input arguments to function include colon operator. To input the colon character, use ':' instead.

Error in fmincon (line 635) initVals.nceq = ceqtmp(:);

Error in flattop (line 15) [x, fval] = fmincon(func,x0,A,b,Aeq,beq,lb,ub,nonlcon);

Error in Load_Shift_Flat (line 118) [pnew, tstart, tending] = flattop(peak_load,tsta,tend,pmax,e(i-1));

I'm trying to optimize for 3 variables and l is an array which is an input to the flattop function

[Walter Roberson]

It looks like the problem is in your nonlcon. What have you passed there?

The error would be consistent with your nonlcon returning a function handle when a value is expected.

[SG]

So it is a function which uses 2 global variables from the workspace

 function [c,ceq] = areaunderc(x)
global ene;
global l;
energ = ene;
c = [];
ceq = @(x)integral(@(l)(l - x(1)),x(2),x(3)) - energ;
end

Answer 1

[Walter Roberson]

Remove the @(x) in the definition of ceq in your nonlcon. You are returning a handle to a function where you need to return a definite value for the current input.