pcomb

A lightweight parser combinator library written in C++14.

Features

• Efficiency is not the goal of this library. After all, parsing is almost never a perfomrance bottleneck of a program analysis system.
• That being said, I try to avoid using heap allocation as much as possible. Most part of the parser is implemented with template metaprogramming and a small part is implemented using class inheritance
• The library is header-only. This is, of course, a direct consequence of TMP.
• Check examples/calc.cc for a simple calculator example.

Usage

• Basic parser

using namespace pcomb;

auto matchAChar = ch('a');
auto matchAString = str("string");
auto matchARangeOfChar = range('a', 'z');
auto matchANumber = regex("[+-]?\\d+");  // the given regex should be in ECMAScript syntax
auto matchAToken = token(str("token"));  // token() gnore preceding whitespaces before parsing the input 

• Combinators

using namespace pcomb;

// Concatenation
auto matchAfollowedbyBfollowedbyC = seq(ch('A'), ch('B'), ch('C'));
// Choice
auto matchAorBorC = alt(ch('A'), ch('B'), ch('C'));
// Repeat
auto matchZeroOrMoreA = many(ch('A'));
auto matchOneOrMoreB = many(ch('B'), true);

• Parser attributes

using namespace pcomb;

auto matchNumber = rule(
	token(many(range('0', '9'), true)),
	[] (auto digitVec)
	{
		return std::stoi(std::string(digitVec.begin(), digitVec.end()));
	}
}
);

• Recursive grammars

using namespace pcomb;

// In C++, a variable cannot be used to initialize itself.
// This is why when we have a recursive non-terminal we need to declare it first before we fill in the details later
// You must explicitly specify the attribute type when you create a LazyParser
auto parenChar0 = LazyParser<char>();

auto charOrAnotherParen = alt(
	ch([] { return true; }),
	rule(
		seq('(', parenChar0, ')'),
		[] (auto triple) { return std::get<char>(triple); }
	)
);

auto& parenChar = parenChar0.set(charOrAnotherParen);

Compilers support

pcomb relies on the C++14 standard, which means you have to compile it with

• GCC version >= 4.9
• Clang version >= 3.4 pcomb also relies on two experimental C++1z standard library features: option and string_view. Their implementation is available in libstdc++4.9 so if you are on a Linux machine with up-to-date g++ you're good to go.