Token Type


### Token type implemented by enum and specified as [Regular Expression](https://texonom.com/regular-expression-5827ff6abf584808b6e1c02b7fa5e25f) 
each types are easy to enum or hard to enum (e.g. finite keywords)
- subscript
- expression

[Assign Expression](https://texonom.com/assign-expression-0a48d63df0d64e6e88951f6914a36d19)

- operator
- keywords
- special symbols
- number
- identifier
- whitespace








