Grammar based AST Tree

This project is based on Scala, building AST Tree using Scala Combinator. The project supports Max, Min and arthimetic operators like "+"."-","/","*".

The parser accepts input in form as String and creates intermediate representation (IR) and using evaluator parse the result.

The parser grammar is:

exp_function ← expression | function | variable | conditional
function ← (‘Max’|‘Min’) (‘(" exp_function ‘,’ ‘)’)*
conditional ← ifCondition (thenCondition) ifCondition ← (if|If) (‘(’ exp_function (‘>’ / ‘<’) exp_function ‘(’) thenCondition ← (then|Then|THEN) (exp_function) variable ← (var) (‘(’ [a-zA-Z]+ ‘)’)*
expression ← term ((‘+’ / ‘-’) term)*
term ← factor ((‘’ / ‘/’) factor)
factor ← Number (‘(’ expr ‘)’)*

This grammar supports Max, Min functions, these functions accepts list of exp_functions. The grammar supports variable defination; that can be define as var(x), var(Test_Var), etc.

The grammar also supports if and then condtional, means if(exp>expr) then expr , etc.

Few of sample example based on above grammar can be:

1. Max(Min(11,11+6),Max(12,6,7*2))
2. 2+4-(4*2)
3. (4/2)-(5*2)+ (11-(2+3))
4. Max(var(a_45),var(b),2*15,10+2)
5. if(4<5) then Max(2,10)

The evaluator accepts result of parser and context (as Map object) to get value of variables.

This can extend with other business oriented and aggregation functions.

Future work: Retail DSL in scala