# E4147

Range pattern bounds must satisfy the ordering constraints:

| Pattern | Constraint |
| ------- | ---------- |
| `a..=b` | `a <= b`  |
| `a..<b` | `a < b`   |

## Erroneous example

```{literalinclude} /sources/error_codes/4147_error/top.mbt
:language: moonbit
```

## Suggestion

Make sure the range pattern bounds satisfy the ordering constraints. This can be
usually achieved by swapping the bounds.

```{literalinclude} /sources/error_codes/4147_fixed/top.mbt
:language: moonbit
```