don't copy string
use `with` instead of `let`, use tconc instead of `append`
add comment
expand known simple byte vector
Revert "expand known simple byte vector"

This reverts commit 766c332d108126cd8bc6c23b7a1c68b3a93b8f7b.
It had little effect.
don't use '(nil) for being destructured list
use logical or for upper-case
Merge pull request #15 from KeenS/fast

Making faster