# 
## Overview  

The Euphoria language provides one with so many handy methods which carry out really important functions in our programs. In this shot, we'll look at the `valid_index()` method. 
## The `valid_index()` method

The **`valid_index` method** is a built-in method in Euphoria used to check if an index is valid. It checks if an index can be found in a sequence variable. When the `valid_indexd()` method checks in a sequence to see if a provided index value makes sense (that is can be found in the sequence), it returns integer value `1` if `true`,  and if `false`, it returns `0`.

## Syntax 

```
 valid_index(search_sequence, index)
```

## Parameters
* `search_sequence`: This is the sequence which will be checked to ascertain if a particular index is found in it.
* `index`: This is the index whose validity is being checked for.

## Return value
This function returns an integer value of `1` if the index is valid and `0` if it is not. 

## Example 
  

--include the required module in the code
include std/sequence.e

sequence search_sequence = "This is the search sequence" 

--valid index instance
atom output1 = valid_index(search_sequence,3) 

--invalid index instance
atom output2 = valid_index(search_sequence,70) 

--this if block show example of a valid index
if  (output1 = 1 ) then 
   printf(1,"it is a valid index, output1 is  : %d\n",output1)
else
   printf(1,"\n it is not valid : %d", output1)

end if 

--while this if block here show example of an invalid index
if(output2 = 0) then
      printf(1,"it is not a valid index, output2 is : %d",output2)
end if


#    
## Explanation
* Line 2 : We include the required module in the code snippet. 
* Line 4: We declare the `search_sequence` variable. 
* Line 7–9: We use the `valid_index()` method and save the outcomes in `output1` and `output2` respectively.
* Lines 13–18: We use an `if` block to show the example of a valid index.
* Lines 21–23: We use another `if` block to show the example of an invalid index.

euphoria.tar.gz

Check for a sequence index using valid_index() in Euphoria

The `valid_index()` method checks if an index is valid within a sequence, returning 1 for true and 0 for false.

Check for a sequence index using valid_index() in Euphoria

Overview

The valid_index() method

Syntax

Parameters

Return value

Example

Explanation

The `valid_index()` method