Same code, different result????

I made a code calculating a numerical integration of a function as the professor taught, but it made an error and couldn't get answer

but when the TA tried it with my code, just copying and pasting, she got a corect answer, while I could not:(

What's the problem

Below is my code:

clc

function f_int=trapezoid(ta,tb,n)
format long
dt=(tb-ta)/n; t=ta;

sum=0.;
sum=func(t);

for i=1:n-1
    t=t+dt; sum=sum+2.0*func(t); 
end

t=t+dt; sum=(sum+func(t))*dt/2;
[sum]
end

function fv=func(t)
fv=1-exp(-2*t); end

(and the file name is also 'trapezoid.m')

I know I have to input the values of ta,tb and n on the command tab, so I typed several sets of numbers but none of them gave me answers but this error:

오류: 파일: trapezoid.m 라인: 3 열: 16

함수 'trapezoid'이(가) 이미 이 범위 내에 선언되어 있습니다.

(It means function 'trapezoid' is already proclaimed in the region)

Answer 1

[Sai Sri Pathuri]

In your script trapezoid, the function trapezoid is treated as a local function and hence, it cannot have same name as that of script.

clc % This is treated as command to be executed and trapezoid, func are local function

function f_int=trapezoid(ta,tb,n)
% code
end

function fv=func(t)
% code
end

This issue can be ressolved in two ways

1. You may remove clc from the script
2. You may change the name of script and call the function after clc command

    clc 
    f_int=trapezoid(ta,tb,n); % Replace ta, tb, n by suitable values
    
    function f_int=trapezoid(ta,tb,n)
    % code
    end
    
    function fv=func(t)
    % code
    end