# index() function

The index() function searches through
a given *str.exp* for the occurrence of the character
or substring specified by *substr.exp* and if found,
returns the numeric position where the nth occurrence of the substring
begins. Null strings are skipped.

## Syntax

```
index(str.exp, substr.exp, num.exp)
```

## Parameter(s)

| str.exp | String to search. |
| --- | --- |
| substr.exp | Character or substring to search for in str.exp. |
| num.exp | Specifies the particular occurrence of the character or substring to find (nth occurrence). If not found, 0 is returned. |

## Description

Note: Searching for a null in
any string returns a result of 1.

## Example(s)

This returns the value 4 to the
variable test, because the first occurrence of `d` is
found in the fourth position of the string.

```
d.position = index("abcdefg","d",1)
```
This example exploits the fact that index() returns a number indicating the position of the search character.
For instance, if response is the letter `d`, then it
goes to statement label 40.

```
on index("abcdefg",response,1) goto 10,20,30,40,50,60,70
```
If `ans` is not null and is either an `a`, `b`, `c`, `ab`, or `bc`, the loop is terminated. Notice that the
null condition must be tested separately because a null value for `ans` results in a 1 from the index() function.

```
loop
input ans,1
until ans#’’ and index(’abc’,ans,1) do repeat
```

## See also

- [BASIC functions](https://d3codex.com/pickbasic-flashbasic/basic-functions/)
- [Numeric expressions](https://d3codex.com/pickbasic-flashbasic/numeric-expressions/)
- [Statements and functions](https://d3codex.com/pickbasic-flashbasic/statements-and-functions/)

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Source: https://d3codex.com/pickbasic-flashbasic/index-function/ - part of the D3Codex reference.