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Transformation Operators - typeof going weird
f#

Consider the folowing code :

open System
open System.Collections.Generic
open Microsoft.FSharp.Core.Operators

let foo (t:System.Type) =
match t with
| typeof<System.Single> -> "Single"
| _ -> "Any type"

Don't compile. I Get the error "Unexpected identifier in pattern. Expected infix operator, quote symbol or other token"

Consider now this sample code :

let foo2 (t:System.Type) =
let x = typeof<System.Single>
match t with
| x -> "Single"
| _ -> "Any type"

Compiles but says for the last rule that it will never be matched.

Did i something wrong ?

Many thanks.

Russell

.

Someone else already posted the correct way to do what you're trying here (using the :? pattern for type testing).

I just wanted to point out that in this code:

let x = typeof<System.Single>
match t with
| x -> "Single"

the second 'x' is a fresh pattern variable (shadowing the first 'x') which will match anything (which explains the compiler warning about further rules never being matched).

By on 9/10/2008 4:11 PM ()
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let foo (t: obj) =
  match t with
  | :? System.Single -> "Single"
  | _ -> "Any type"
By on 9/10/2008 3:35 PM ()

yes I know about the :? operator, but I need a function that takes a System.Type as an input.

thanks,

Russell

By on 9/10/2008 4:14 PM ()
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let foo (t: System.Type) =
  match t with
  | _ when t = typeof<float32> -> "Single"
  | _ -> "Any type"
By on 9/10/2008 4:23 PM ()

Works now! Thanks yashez!

brian: ok I understood my mistake, thanks!

By on 9/10/2008 4:30 PM ()

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