function reference file

I need to create a function reference file to be used by the following function, where f is the function name, a b lower and upper limit, and num is the number of intervals. I am new to matlab, and do not know how the reference file should be set up. Thanks in advance.

[area] = trapezoidal(f,a,b,num);

dx = (b-a)/num ; 
x = a:dx:b;

for i = 1:length(x)
    y(i) = f(x(i));
end

for i = 2: length(x) - 1
    area = ((y(i)+y(i+1))/2)*dx + ((y(1)+y(2))/2)*dx + ((y(end-1)+y(end))/2)*dx ;
end

Answer 1

[Jiro Doke]

Read about "Function Handles" here.