# Function calls

Gel provides a number of functions in the [standard library](https://docs.geldata.com/reference/stdlib.md#ref-std). It is also possible for users to [define their own](https://docs.geldata.com/reference/datamodel/functions.md#ref-eql-sdl-functions) functions.

The syntax for a function call is as follows:

```edgeql-synopsis
<function_name> "(" [<argument> [, <argument>, ...]] ")"

# where <argument> is:

<expr> | <identifier> := <expr>
```

Here `<function_name>` is a possibly qualified name of a function, and `<argument>` is an *expression* optionally prefixed with an argument name and the assignment operator (`:=`) for [named only](https://docs.geldata.com/reference/datamodel/functions.md#ref-eql-sdl-functions-syntax) arguments.

For example, the following computes the length of a string `'foo'`:

```edgeql-repl
db> select len('foo');
{3}
```

And here's an example of using a *named only* argument to provide a default value:

```edgeql-repl
db> select array_get(['hello', 'world'], 10, default := 'n/a');
{'n/a'}
```

|                                                                                                                                            |
| ------------------------------------------------------------------------------------------------------------------------------------------ |
| **See also**                                                                                                                               |
| [Schema > Functions](https://docs.geldata.com/reference/datamodel/functions.md#ref-datamodel-functions)                                    |
| [SDL > Functions](https://docs.geldata.com/reference/datamodel/functions.md#ref-eql-sdl-functions)                                         |
| [DDL > Functions](https://docs.geldata.com/reference/datamodel/functions.md#ref-eql-ddl-functions)                                         |
| [Introspection > Functions](https://docs.geldata.com/reference/datamodel/introspection/functions.md#ref-datamodel-introspection-functions) |
| [Cheatsheets > Functions](https://docs.geldata.com/resources/cheatsheets/functions.md#ref-cheatsheet-functions)                            |