# E4137

Range operators are currently only supported in `for .. in` loops.

This means you cannot save the range operator in a variable or use it later in
other contexts.

## Erroneous example

```{literalinclude} /sources/error_codes/4137_error/top.mbt
:language: moonbit
```

## Suggestion

One can use the `until` method to generate a range of numbers:

```{literalinclude} /sources/error_codes/4137_fixed/top.mbt
:language: moonbit
```