Add documentation for Array.head (#275)

docs/conceptual/array.head['t]-function-[fsharp].md

@@ -0,0 +1,68 @@
+---
+title: Array.head<'T> Function (F#)
+description: Array.head<'T> Function (F#)
+keywords: visual f#, f#, functional programming
+author: erikschierboom
+manager: danielfe
+ms.date: 03/12/2017
+ms.topic: language-reference
+ms.prod: visual-studio-dev14
+ms.technology: devlang-fsharp
+ms.assetid: 3c376852-11f0-4286-9210-6d8a719ae626
+---
+
+# Array.head<'T> Function (F#)
+
+Returns the first element of the array.
+
+**Namespace/Module Path:** Microsoft.FSharp.Collections.Array
+
+**Assembly:** FSharp.Core (in FSharp.Core.dll)
+
+
+## Syntax
+
+```fsharp
+// Signature:
+Array.head : 'T[] -> 'T
+
+// Usage:
+Array.head array
+```
+
+#### Parameters
+*array*
+Type: **'T**[[]](https://msdn.microsoft.com/library/def20292-9aae-4596-9275-b94e594f8493)
+
+
+The input array.
+
+## Exceptions
+
+|Exception|Condition|
+|----|----|
+|[ArgumentException](https://msdn.microsoft.com/library/system.argumentexception.aspx)|Thrown when the array is empty.|
+
+## Return Value
+
+The first element of the array.
+
+## Remarks
+Raises `System.ArgumentException` if *array* is empty
+
+This function is named `Head` in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.
+
+## Platforms
+Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2
+
+
+## Version Information
+**F# Core Library Versions**
+
+Supported in: 4.0, Portable
+
+
+## See Also
+[Collections.Array Module &#40;F&#35;&#41;](Collections.Array-Module-%5BFSharp%5D.md)
+
+[Microsoft.FSharp.Collections Namespace &#40;F&#35;&#41;](Microsoft.FSharp.Collections-Namespace-%5BFSharp%5D.md)

docs/conceptual/collections.array-module-[fsharp].md

@@ -60,6 +60,7 @@ For an overview of arrays in F#, see [Arrays (F#)](Arrays-%5BFSharp%
 |[`foldBack2`](https://msdn.microsoft.com/library/aa51b405-df20-4c51-9998-a6530f7db862)<br />**: ('T1 -&gt; 'T2 -&gt; 'State -&gt; 'State) -&gt; 'T1 [] -&gt; 'T2 [] -&gt; 'State -&gt; 'State**|Applies a function to pairs of elements from two supplied arrays, right-to-left, threading an accumulator argument through the computation. The two input arrays must have the same lengths; otherwise, **System.ArgumentException** is raised.|
 |[`forall`](https://msdn.microsoft.com/library/d88f2cd0-fa7f-45cf-ac15-31eae9086cc4)<br />**: ('T -&gt; bool) -&gt; 'T [] -&gt; bool**|Tests whether all elements of an array satisfy the supplied condition.|
 |[`forall2`](https://msdn.microsoft.com/library/c68f61a1-030c-4024-b705-c4768b6c96b9)<br />**: ('T1 -&gt; 'T2 -&gt; bool) -&gt; 'T1 [] -&gt; 'T2 [] -&gt; bool**|Tests whether all corresponding elements of two supplied arrays satisfy a supplied condition.|
+|[head](https://msdn.microsoft.com/library/3c376852-11f0-4286-9210-6d8a719ae626)<br />**: 'T [] -&gt; 'T**|Returns the first element of the array.|
 |[`get`](https://msdn.microsoft.com/library/dd93e85d-7e80-4d76-8de0-b6d45bcf07bc)<br />**: 'T [] -&gt; int -&gt; 'T**|Gets an element from an array.|
 |[`init`](https://msdn.microsoft.com/library/ee898089-63b0-40aa-910c-5ae7e32f6665)<br />**: int -&gt; (int -&gt; 'T) -&gt; 'T []**|Uses a supplied function to create an array of the supplied dimension.|
 |[`isEmpty`](https://msdn.microsoft.com/library/c2bd48e9-8aba-4bea-ad84-17352886d3a8)<br />**: 'T [] -&gt; bool**|Tests whether an array has any elements.|