Seq.findIndex

gistfile1.fs

F# Interactive for F# 3.1 (Open Source Edition)
Freely distributed under the Apache 2.0 Open Source License

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> let scale1 = seq { -0.5 .. 0.1 .. 0.5 } ;;

val scale1 : seq<float>

> scale1 |> Seq.toArray ;;
val it : float [] =
  [|-0.5; -0.4; -0.3; -0.2; -0.1; 0.0; 0.1; 0.2; 0.3; 0.4; 0.5|]
> scale1 |> Seq.findIndex (fun e -> e = -0.5) ;;
val it : int = 0
> scale1 |> Seq.findIndex (fun e -> e = -0.4) ;;
val it : int = 1
> scale1 |> Seq.findIndex (fun e -> e = -0.3) ;;
val it : int = 2
> scale1 |> Seq.findIndex (fun e -> e = -0.2) ;;
System.Collections.Generic.KeyNotFoundException: Exception of type 'System.Collections.Generic.KeyNotFoundException' was thrown.
  at Microsoft.FSharp.Collections.SeqModule.loop@1161-16[Double] (Microsoft.FSharp.Core.FSharpFunc`2 p, IEnumerator`1 ie, Int32 i) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Collections.SeqModule.FindIndex[Double] (Microsoft.FSharp.Core.FSharpFunc`2 predicate, IEnumerable`1 source) [0x00000] in <filename unknown>:0
  at <StartupCode$FSI_0007>.$FSI_0007.main@ () [0x00000] in <filename unknown>:0
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
Stopped due to error
>