CODEWITHSUNDEEP
f#
Matheus Miranda
Matheus Miranda

Reputation: 1805

The block after 'let' is unfinished - try/with

Follow Code F#:

try
    let result = 100/0
with
    | :? Exception as ex -> printfn ex.Message

I get an error:

The block after 'let' is unfinished. Each block of code is an expression and must have a result. 'let' can not be the final code element in a block. Consider giving this block an explicit result.

What am I doing wrong ?

Upvotes: 1

Views: 459

Answers (2)

AMieres
AMieres

Reputation: 5004

The issue is that let by itself is not an expression:

In F# everything is an expression of a certain type. But let alone is not an expression, is a binding and it has to be continued with some expression that, presumably, uses the value bound to the id result.

Since you are merely testing the try/catch functionality. I assume you are not really interested in producing any values, that is why I added the expression: () after the let.

try
    let result = 100/0
    ()
with
    ex -> printfn "%s" ex.Message

The try/with expression requires that both sides return the same type of value, just like if/then/else does. Since in the with side printfn returns unit, I made the try side also return a unit value which is (). Think of it as the equivalent to void in C#.

Upvotes: 8

m0nhawk
m0nhawk

Reputation: 24178

I can recommend different approach. This won't leave the result variable undefined.

let result =
    try
        Some(100/0)
    with
        | :? Exception as ex -> printfn "%s" ex.Message; None

Upvotes: 2

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