Fix one assert, and adapt style of others as well

- the `<= len()` was wrong

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Whitespace

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added add bytecode to improve interpreter performance

Signed-off-by: Stefan Marr <git@stefan-marr.de>