Refactor string parser and lexer: mainly for webapp usage

[ryukinix]

• It should tokenize tokens first based on operations, supporting concatenated (without whitespaces) exps like this: p^q.
• It should use a LL(1) parser
• It should supports parenthesis without any problem
• It should fail early instead of trying be clever.

Example:

In: "p^q=>r" 
Out: (=> (^ p q) r)

[leonardohn]

Well, you could use an LL(1) parser to read the expression precedence and give you a polish notation expression. Try using this website to test this grammar:

D' -> v C D'
D' -> ''
C -> I C'
C' -> ^ I C'
C' -> ''
I -> E I'
I' -> => E I'
I' -> ''
E -> N E'
E' -> <=> N E'
E' -> ''
N -> ~ A
N -> A
A -> ( P )
A -> id

[ryukinix]

Thank you for this contribution! A formal parser will be really useful!

[ryukinix]

The parsing table it is:

[ryukinix]

Runtime parsing steps.

[ryukinix]

Maybe can be useful: https://github.com/vy/meta-sexp