Arithmetic casting to generic type in F# -

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i try write function generic casting arithmetic types, example function receives argument of type uint64, converts type being same type parameter. idea is:

let convert<'t> (x:uint64) = 't x

but code not compile, , stuck here after trying several approaches like:

let convert<'t> (x:uint64) =    match unchecked.defaultof<'t>      | :? uint32 -> uint32 x ....

so how write such generic arithmetic casting in f#? (i start learning question maybe stupid, please take easy).

you can use static member constraints, here's "short" example:

type explicit =     static member inline ($) (_:byte , _:explicit) = byte                 static member inline ($) (_:sbyte, _:explicit) = sbyte                static member inline ($) (_:int16, _:explicit) = int16                static member inline ($) (_:int32, _:explicit) = int     // more overloads  let inline convert value: 't =      (unchecked.defaultof<'t> $ unchecked.defaultof<explicit>) value  // specialized uint64 let inline fromuint64 (value: uint64) :'t = convert value  // usage let x:int = fromuint64 7ul

as said in comments can use function explicit f#+ covers cases when there explicit operator. here's sample code.

now if @ source code of function defined in project (fscontrol) find more complicated workaround.

you may wonder why, here's long answer:

in theory should possible use single call invoking member op_explicit, work when member exists not case native number types.

for cases f# compiler uses feature referred "simulated members" implemented using static optimizations that's not available outside f# compiler source code.

so fscontrol uses different feature instead: overload resolution, in sample code showed uses additional overload general case members contain op_explicit static member.


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