ExpressionCalculator

This is and experiment to write a simple LL(1) parser without parsing table, but with set of rules implemented using std::variant and visitor concept.

The set of terminals are defined in Lexer.h and the simplistic lexer is implemented in Lexer.cpp The rules for LL(1) parser are defined in Parser.cpp

EBNF Grammar is as below:

     E -> T {op1 T}*
     T -> F {op2 F}*
     F -> number | op1 F | '(' E ')'

This is further converted to the following BNF LL(1) grammar

     E  -> T E'
     E' -> $ | bin_op1 T E'
     T  -> F T'
     T' -> $ | bin_op2 F T'
     F  -> number | bin_op1 F | '(' E ')'

References

• Sum types and state machines in C++17
• LLVM Kaleidoscope: Implementing a Parser and AST

Status

Branch / Compiler	MSVC 2017
master