CODEWITHSUNDEEP
castingf#
Marko Grdinić
Marko Grdinić

Reputation: 4062

How to cast to a type abbreviation?

type floatType = float32
let a = 5.0
let b = float32 a // Works
let b' = floatType b // Does not work

Would it be possible to cast to a type abbreviation?

Upvotes: 1

Views: 384

Answers (2)

Gus
Gus

Reputation: 26174

Yes, it's possible to use a type alias for casting, but you're not casting, that's not the syntax for casting. In your example you're using an explicit conversion.

Casting is a different thing, it "converts" to a super-class (up-casting) or a sub-class (down-casting), see this modification of your example:

type floatType = float32
let a = box 5.0f 
let b  = a :?> float32
let b' = a :?> floatType

This example is down-casting and as you can see it works with the alias.

So it's not possible to cast from float to float32, even without type annotations.

Upvotes: 4

Vandroiy
Vandroiy

Reputation: 6223

When writing float32 a, you are using the function Microsoft.FSharp.Core.Operators.float32, which does an explicit conversion to a single-precision float without units.

If you want to allow similar usage of floatType, you could add the following to your definitions:

let inline floatType a = float32 a

Now your code should work.

Upvotes: 2

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