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# 0117: Invalid function name

Compiler found a [function declaration](/language/functions.md#signature) with the name that is not a valid identifier. A function name must be alphanumeric starting with a letter or an underscore (`_`).

#### Examples:

```pascal
function 123 // Error: Invalid function name 123. Name must be a valid identifier.
end
```

#### Possible solutions:

* Rename the function so that its name is a valid identifier:

```pascal
function f123
end
```