# IntPtr.Subtract(IntPtr, Int32) Method

## Definition

Subtracts an offset from a signed integer.

``````public:
static IntPtr Subtract(IntPtr pointer, int offset);``````
``public static IntPtr Subtract (IntPtr pointer, int offset);``
``static member Subtract : nativeint * int -> nativeint``
``Public Shared Function Subtract (pointer As IntPtr, offset As Integer) As IntPtr``

#### Parameters

pointer

nativeint

The signed integer to subtract the offset from.

offset
Int32

The offset to subtract.

#### Returns

nativeint

A new signed integer that reflects the subtraction of `offset` from `pointer`.

## Examples

The following example instantiates an IntPtr object that points to the end of a ten-element array, and then calls the Subtract method to iterate the elements in the array in reverse order.

``````using System;
using System.Runtime.InteropServices;

public class Example
{
public static void Main()
{
int[] arr = { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
// Get the size of a single array element.
int size = sizeof(int);
unsafe {
fixed(int* pend = &arr[arr.GetUpperBound(0)]) {
IntPtr ptr = new IntPtr(pend);
for (int ctr = 0; ctr < arr.Length; ctr++)
{
IntPtr newPtr = IntPtr.Subtract(ptr, ctr * size);
}
}
}
}
}
// The example displays the following output:
//       20   18   16   14   12   10   8   6   4   2
``````
``````#nowarn "9"
open System
open System.Runtime.InteropServices
open FSharp.NativeInterop

[<EntryPoint>]
let main _ =
let arr =
[| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]

// Get the size of a single array element.
let size = sizeof<int>

use pend = fixed &arr[arr.GetUpperBound 0]
let ptr = NativePtr.toNativeInt pend
for i = 0 to arr.Length - 1 do
let newPtr = IntPtr.Subtract(ptr, i * size)
0

// The example displays the following output:
//       20   18   16   14   12   10   8   6   4   2
``````
``````Imports System.Runtime.InteropServices

Module Example
Public Sub Main()
Dim arr() As Integer = { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20}
Dim ptr As IntPtr = Marshal.UnsafeAddrOfPinnedArrayElement(arr, arr.Length - 1)
Dim size As Integer = Len(arr(0))

For ctr As Integer = 0 To arr.Length - 1
Dim newPtr As IntPtr = IntPtr.Subtract(ptr, ctr * size)
Next
End Sub
End Module
' The example displays the following output:
'       20   18   16   14   12   10   8   6   4   2
``````

## Remarks

The Subtract method does not throw an exception if the result is too small to represent as a signed integer in the executing process. Instead, the subtraction operation is performed in an unchecked context.

Languages that do not support operator overloading or custom operators can use this method to subtract an offset from the value of a pointer.