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.
- 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).
buffalo officially supports the following compilers:
- GCC 14
- Clang 18
- MSVC
/* 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;
bf::Terminal<G> terminals[] = { NUMBER, OP_EXP, OP_MUL, OP_DIV, OP_ADD, OP_SUB, PAR_OPEN, PAR_CLOSE };
bf::CTRETokenizer tokenizer(std::to_array(terminals));
/*
* 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(tok, statement);
double result = *calculator.Parse("18 + 2^(1 + 1) * 4");