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Does mkSeq make a sequence?
f#

While using mkSeq as defined in seq.fs I ran into something I don't understand. For example

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open System.Collections
open System.Collections.Generic

let mkSeq f = 
  { new IEnumerable<'U> with 
      member x.GetEnumerator() = f()
    interface IEnumerable with 
      member x.GetEnumerator() = (f() :> IEnumerator) }

let test (s : seq<int>) =
    seq {
        let e = s.GetEnumerator()
        yield! mkSeq (fun () -> e)
        }

when evaluated, for example, as 

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test {1..3}

generates an assertion failure. The error message starts

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ERROR:class.c:2641:mono_class_setup_vtable: assertion failed: (inflated)
Stacktrace:

  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1<int>.MoveNextImpl () <0xffffffff>
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1<int>.MoveNextImpl () <0x0004a>
  at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1<int>.System-Collections-IEnumerator-MoveNext () <0x00010>

Any idea what is going on?

Thanks.

.

Your code works in Visual Studio, so I'd guess this is a problem with Mono.

-Keith

By on 11/8/2009 10:34 AM ()

Thanks. You're right. I just tried it with F# 1.9.6 and 1.9.7 on .NET and it worked fine. Given that constructs similar to what I wrote are used in the F# sources (for example in seq.fs) I suspect that Mono is not a viable platform for F# at the moment.

By on 11/8/2009 4:20 PM ()

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