Practice question from Immutability & Expressions

Complete the recursive function to sum a list:

let ____ sum lst =
    match lst with
    | [] -> 0
    | head :: tail -> head + sum tail

Answer

["rec"]

Explanation

The 'rec' keyword tells F# that this function is recursive (calls itself). Without 'rec', the function name wouldn't be in scope within its own body, causing a compiler error.

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