CODEWITHSUNDEEP
typesf#parameterstype-inference
Kirk Broadhurst
Kirk Broadhurst

Reputation: 28698

Explicitly specifying parameter types in F#

I'm writing an F# function that factorises a number into prime factors.

let factors primes i =
    let mutable j = i
    for p in primes do 
        while (j>1) && (j%p=0) do 
            j <- j/p
            printfn "prime: %i" p

It works for int values of i, but not int64 values. The parameter primes is a set of int values.

I understand why this is the case - type inference is assuming that the function only takes int parameters - but I want to explicitly specify the parameter type as int64.

Is it possible to write this function so that it will work for both int and int64?

Upvotes: 3

Views: 2209

Answers (2)

kvb
kvb

Reputation: 55184

If you want to work only on int64 values, just replace 1 and 0 with 1L and 0L respectively. jpalmer's answer covers the generic case.

Upvotes: 5

John Palmer
John Palmer

Reputation: 25516

You will have to do something like

let inline factors (primes :^a list) (i:^a) =
    let zero:^a = LanguagePrimitives.GenericZero
    let one:^a = LanguagePrimitives.GenericOne
    let mutable j = i
    for p in primes do 
        while (j>one) && (j%p=zero) do 
            j <- j/p
            printfn "prime: %i" p

I don't have the compiler, so my syntax may be slightly off

Upvotes: 8

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