CODEWITHSUNDEEP
f#
Antonio
Antonio

Reputation: 11

F# If-Then-Else trouble

let downTo n = 

    if (n.Equals(0)) then
        printfn "\n Empty List Provided \n";;
    else
        List.rev(List.init n (fun index -> index + 1));;

I'm trying to create a list 'n' length, if a number greater than 0 is passed. If not, print an error message. The List works by itself, but not in the If-Else statement. How can this be accomplished? Please help.

Upvotes: 1

Views: 488

Answers (1)

N_A
N_A

Reputation: 19897

F# if expressions are expressions not statements. What this means is that the two parts of the expression need to have the same type. In this case, one side has a type of int list and the other side has a type of unit.

Something like this would work for you better:

let downTo n =
    if (n.Equals(0)) then
        printfn "\n Empty List Provided \n"
        []
    else
        List.rev(List.init n (fun index -> index + 1))

or, alternatively, you could throw an exception but this has the drawback that you have to do a try/catch around it.

Upvotes: 6

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