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Visual F#
Visual F# Development Portal
What's new in Visual F#
Visual F# Guided Tour
Using Visual Studio to Write F# Programs
F# Language Reference
F# Compiler (fsc.exe) Reference
F# Interactive (fsi.exe) Reference
F# Core Library Reference
Microsoft.FSharp.Collections Namespace
Array Module
Array2D Module
Array3D Module
Array4D Module
ComparisonIdentity Module
HashIdentity Module
List Module
List.append<'T> Function
List.average<^T> Function
List.averageBy<'T,^U> Function
List.choose<'T,'U> Function
List.chunkBySize<'T> Function
List.collect<'T,'U> Function
List.compareWith<'T> Function
List.concat<'T> Function
List.contains<'T> Function
List.countBy<'T,'Key> Function
List.distinct['t] Function
List.empty<'T> Type Function
List.exists<'T> Function
List.exists2<'T1,'T2> Function
List.filter<'T> Function
List.find<'T> Function
List.findIndex<'T> Function
List.fold<'T,'State> Function
List.fold2<'T1,'T2,'State> Function
List.foldBack<'T,'State> Function
List.foldBack2<'T1,'T2,'State> Function
List.forall<'T> Function
List.forall2<'T1,'T2> Function
List.head<'T> Function
List.init<'T> Function
List.isEmpty<'T> Function
List.iter<'T> Function
List.iter2<'T1,'T2> Function
List.iteri<'T> Function
List.iteri2<'T1,'T2> Function
List.length<'T> Function
List.map<'T,'U> Function
List.map2<'T1,'T2,'U> Function
List.map3<'T1,'T2,'T3,'U> Function
List.mapi<'T,'U> Function
List.mapi2<'T1,'T2,'U> Function
List.max<'T> Function
List.maxBy<'T,'U> Function
List.min<'T> Function
List.minBy<'T,'U> Function
List.nth<'T> Function
List.ofArray<'T> Function
List.ofSeq<'T> Function
List.partition<'T> Function
List.permute<'T> Function
List.pick<'T,'U> Function
List.reduce<'T> Function
List.reduceBack<'T> Function
List.replicate<'T> Function
List.rev<'T> Function
List.scan<'T,'State> Function
List.scanBack<'T,'State> Function
List.sort<'T> Function
List.sortBy<'T,'Key> Function
List.sortWith<'T> Function
List.splitAt<'T> Function
List.sum<^T> Function
List.sumBy<'T,^U> Function
List.tail<'T> Function
List.toArray<'T> Function
List.toSeq<'T> Function
List.tryFind<'T> Function
List.tryFindIndex<'T> Function
List.tryPick<'T,'U> Function
List.unzip<'T1,'T2> Function
List.unzip3<'T1,'T2,'T3> Function
List.zip<'T1,'T2> Function
List.zip3<'T1,'T2,'T3> Function
list<'T> Type Abbreviation
List<'T> Union
Map<'Key,'Value> Class
Collections.Map Module
Collections.ResizeArray<'T> Type Abbreviation
Collections.Seq Module
Collections.seq<'T> Type Abbreviation
Collections.Set<'T> Class
Collections.Set Module
Microsoft.FSharp.Control Namespace (F#)
Microsoft.FSharp.Core Namespace (F#)
Microsoft.FSharp.Core.CompilerServices Namespace (F#)
Microsoft.FSharp.Data Namespace
Microsoft.FSharp.Linq Namespace (F#)
Microsoft.FSharp.NativeInterop Namespace (F#)
Microsoft.FSharp.Quotations Namespace (F#)
Microsoft.FSharp.Reflection Namespace (F#)
System Namespace (F#)
System.Collections Namespace (F#)
System.Numerics Namespace (F#)
System.Threading Namespace (F#)
Visual F# Samples and Walkthroughs
Type Providers (F#)
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List.tryFind<'T> Function (F#)

Den Delimarsky|Last Updated: 8/18/2017
|
1 Contributor

Returns the first element for which the given function returns true. Returns None if no such element exists.

Namespace/Module Path: Microsoft.FSharp.Collections.List

Assembly: FSharp.Core (in FSharp.Core.dll)

Syntax

// Signature:
List.tryFind : ('T -> bool) -> 'T list -> 'T option

// Usage:
List.tryFind predicate list

Parameters

predicate Type: 'T ->bool

The function to test the input elements.

list Type: 'Tlist

The input list.

Return Value

The first element for which the predicate returns true, or None if every element evaluates to false.

Remarks

This function is named TryFind in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.

Example

let list1d = [1; 3; 7; 9; 11; 13; 15; 19; 22; 29; 36]
let isEven x = x % 2 = 0
match List.tryFind isEven list1d with
| Some value -> printfn "The first even value is %d." value
| None -> printfn "There is no even value in the list."

match List.tryFindIndex isEven list1d with
| Some value -> printfn "The first even value is at position %d." value
| None -> printfn "There is no even value in the list."

Output

The first even value is 22.
The first even value is at position 8.

Platforms

Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

Version Information

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

See Also

Collections.List Module (F#)

Microsoft.FSharp.Collections Namespace (F#)

© 2018 Microsoft