buffalo

‍buffalo: to bewilder, baffle (also: bamboozle) [2024 Merriam-Webster Dictionary]

Bewilder, baffle (even bamboozle!) your grammars with buffalo, a C++23 header-only SLR parser generator with yacc/bison-like syntax.

It supports the definition of terminals, non-terminals and grammar structures all within the same C++ file.

Features

• Terminal definition with builtin scanning based on compile-time-regular-expressions (spex).
• Grammar definition in pseudo BNF notation.
• Shift/Reduce conflict resolution through precedence (based on definition order) and associativity (left/right/none).

Compiler Support

buffalo officially supports the following compilers:

• GCC 14
• Clang 18
• MSVC

Examples

Calculator

 ++
/* calculator.cpp */
#include <buffalo/buffalo.h>
#include <buffalo/spex.h>
 
/*
 * Grammar Definition
 */
using G = bf::GrammarDefinition<double>;
 
/*
 * Terminals
 */
bf::DefineTerminal<G, R"(\d+(\.\d+)?)", double> NUMBER([](auto const &tok) {
    return std::stod(std::string(tok.raw));
});
 
bf::DefineTerminal<G, R"(\^)"> OP_EXP(bf::Right);
 
bf::DefineTerminal<G, R"(\*)"> OP_MUL(bf::Left);
bf::DefineTerminal<G, R"(\/)"> OP_DIV(bf::Left);
bf::DefineTerminal<G, R"(\+)"> OP_ADD(bf::Left);
bf::DefineTerminal<G, R"(\-)"> OP_SUB(bf::Left);
 
bf::DefineTerminal<G, R"(\‍()"> PAR_OPEN;
bf::DefineTerminal<G, R"(\))"> PAR_CLOSE;
 
/*
 * Non-Terminals
 */
bf::DefineNonTerminal<G> expression
    = bf::PR<G>(NUMBER)<=>[](auto &$) { return $[0]; }
    | (PAR_OPEN + expression + PAR_CLOSE)<=>[](auto &$) { return $[1]; }
    | (expression + OP_EXP + expression)<=>[](auto &$) { return std::pow($[0], $[2]); }
    | (expression + OP_MUL + expression)<=>[](auto &$) { return $[0] * $[2]; }
    | (expression + OP_DIV + expression)<=>[](auto &$) { return $[0] / $[2]; }
    | (expression + OP_ADD + expression)<=>[](auto &$) { return $[0] + $[2]; }
    | (expression + OP_SUB + expression)<=>[](auto &$) { return $[0] - $[2]; }
    ;
 
bf::DefineNonTerminal<G> statement
    = bf::PR<G>(expression)<=>[](auto &$)
    {
        return $[0];
    }
    ;
 
/*
 * Calculations
 */
auto calculator = bf::SLRParser<G>::Build(statement);
double result = *calculator.Parse("18 + 2^(1 + 1) * 4");