This is already a primitive! Just use
The definition is also unnecessarily complicated.
Also, if you turn off the negative? and decimal? flags, the block basically loses all meaning, since it just reports 1. Why even have those?
There's a much simpler way to make this definition:
The "reverse string" block is missing a definition.
This can be done much more easily:
...What?
Why don't you just use 
?
Can be simplified:
