# Guard Clauses and Range Validation

A guard clause exits early when input is invalid.

## Example from your snippet

```ts
if (rangeStart !== undefined && rangeEnd !== undefined && rangeStart > rangeEnd) {
  return [];
}
```

## Why this is good

- Fails fast.
- Prevents harder-to-debug logic later.
- Keeps the main flow cleaner.

## Operator notes

- `!==`: strict "not equal" comparison.
- `&&`: logical AND (all conditions must be true).
- `>`: greater-than comparison.

## Python comparison

```py
if range_start is not None and range_end is not None and range_start > range_end:
    return []
```