MATLAB: I have an error on the following code.how to rectify the error

function

if true
clc;
clear all;
close all;
c = Ns;
d= 8;
z = f(c, d)
function z = f(c,d)
if ~mod(c,d)
  z=0
else
  z=d-mod(c,d);
end
end
end

function z =  myfunction(Ns)
c = Ns;
d= 8;
z = f(c, d)
end
function z = f(c,d)
if ~mod(c,d)
  z=0
else
  z=d-mod(c,d);
end
end

Call the function:

Ns = rand ;  % any value
z = myfunction(Ns) ;

function z = myfunction(Ns)
c = Ns;
d= 8;
z =f(c, d) ;
end
function z = f(c,d)
if ~mod(c,d)
    z=0
else
    z=d-mod(c,d);
end
end

Save it.....it will be saved as myfunction.m. Call z = myfunction(3) ;

MATLAB documentation tells you how to make functions. Like, to make your "f" function you'd do this:

function z = f(a, b)
if ~mod(a,b)
    z=0
else
    z=b-mod(a,b);
end

To call it, you'd do this:

a = Ns;
b = 8;
z = f(a, b)