Recursive functions

This lesson covers writing a recursive function in Julia, with the aim of understanding how a function can call itself.

A recursive function is one that calls itself. It suits work that repeats the same pattern of calculation, such as "n! = n × (n-1)!".

In the sample code, factorial_j calls itself as n * factorial_j(n - 1) to calculate 5 factorial. The finishing condition if n <= 1 return 1 end is what makes the calls stop somewhere.

A common early stumble is forgetting the finishing condition. Without one, the function calls itself forever and the program dies.

In professional work, deep recursion consumes a great deal of stack, so it is worth considering whether a loop would do instead.

📖 Reference code

function factorial_j(n)
    if n <= 1
        return 1
    end
    n * factorial_j(n - 1)
end
println(factorial_j(5))

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Julia directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).