Local functions in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a script with local function call

What is the output of this MATLAB script when run?

MATLAB

disp(mainFunction())

function out = mainFunction()
    out = helperFunction(5);
end

function y = helperFunction(x)
    y = x^2;
end

A 10

B 5

C Error: Undefined function or variable 'helperFunction'.

D 25

💡 Hint

Local functions can be called by functions in the same file.

The mainFunction calls helperFunction with input 5. helperFunction squares it, returning 25.

❓ Predict Output

intermediate

Value of variable after local function modifies it

What is the value of variable 'result' after running this code?

MATLAB

function result = testLocal()
    x = 3;
    result = increment(x);

    function y = increment(a)
        y = a + 2;
    end
end

r = testLocal();

A Error: Undefined function 'increment'.

B 3

C 5

D 2

💡 Hint

Local functions can access variables passed as arguments.

The local function increment adds 2 to input 3, returning 5.

❓ Predict Output

advanced

Output when local function shadows variable

What is the output of this script?

MATLAB

function output = shadowTest()
    x = 10;
    output = localFunc();

    function y = localFunc()
        x = 5;
        y = x + 1;
    end
end

result = shadowTest();
disp(result)

A 6

B 11

C Error: Variable 'x' is undefined.

D 10

💡 Hint

Local function has its own variable 'x' that hides outer 'x'.

Inside localFunc, x is set to 5, so y = 5 + 1 = 6.

❓ Predict Output

advanced

Output of a script with chained local function calls

What is the output of this MATLAB script when run?

MATLAB

disp(outsideCall())

function y = outsideCall()
    y = localOnly();
end

function z = localOnly()
    z = 42;
end

A 42

B 0

C Error: Function 'outsideCall' not found.

D Error: Undefined function or variable 'localOnly'.

💡 Hint

Local functions can call other local functions in the same file.

The script calls outsideCall(), which calls localOnly() returning 42.

🧠 Conceptual

expert

Number of local functions accessible inside a nested function

Given this MATLAB file with three local functions, how many local functions can the nested function 'inner' call directly?

MATLAB

function main()
    disp(inner())

    function a = inner()
        a = f1() + f2() + f3();
    end

    function x = f1()
        x = 1;
    end

    function y = f2()
        y = 2;
    end

    function z = f3()
        z = 3;
    end
end

A 0

B 3

C 1

D 2

💡 Hint

Local functions in the same file are visible to each other.

The nested function 'inner' can call all three local functions f1, f2, and f3 directly.