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parser.hpp
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parser.hpp
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#ifndef PARSER_HPP
#define PARSER_HPP
#include "either.hpp"
#include "unit.hpp"
#include <deque>
#include <functional>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
namespace parser {
// character range
struct range {
const char* first;
const char* last;
range(): first(nullptr), last(nullptr) {}
range(const char* first,
const char* last):
first(first),
last(last) {
assert(first <= last);
}
range(const std::string& contents):
first(contents.data()),
last(contents.data() + contents.size()) { }
range(std::string&&) = delete;
explicit operator bool() const { return first != last; }
std::size_t size() const { return last - first; }
char get() const {
assert(bool(*this));
return *first;
}
range next() const {
assert(bool(*this));
return {first + 1, last};
}
std::string show() const { return {first, last}; }
};
static void peek(range self, std::ostream& out, std::size_t count=42) {
for(std::size_t i = 0; self && (i < count);
++i, self = self.next()) {
out << self.get();
}
}
// successful parse
template<class T>
struct success: range {
using value_type = T;
T value;
success(T value, range rest): range(rest), value(std::move(value)) {}
};
template<class T>
static success<T> make_success(T value, range rest) {
return {std::move(value), rest};
}
// parse error
struct error: range {
error(range at): range(at) {}
};
// parse result
template<class T>
using result = either<error, success<T>>;
// parser value type
template<class Parser>
using value =
typename std::result_of<Parser(range)>::type::value_type::value_type;
// type-erased parser
template<class T>
using monad = std::function<result<T>(range in)>;
////////////////////////////////////////////////////////////////////////////////
// combinators
// monad unit
template<class T>
static auto pure(T value) {
return [value = std::move(value)](range in) -> result<T> {
return make_success(value, in);
};
};
// functor map
template<class Parser, class Func, class=value<Parser>>
static auto map(Parser parser, Func func) {
return [parser = std::move(parser), func = std::move(func)](range in) {
using value_type = typename std::result_of<Func(value<Parser>)>::type;
using result_type = result<value_type>;
return map(parser(in), [&](success<value<Parser>>&& self) {
return make_success(func(std::move(self.value)), self);
});
};
};
template<class Parser, class Func, class=value<Parser>>
static auto operator|=(Parser parser, Func func) {
return map(parser, func);
};
// monad bind
template<class Parser, class Func, class=value<Parser>>
static auto bind(Parser parser, Func func) {
return [parser = std::move(parser), func = std::move(func)](range in) {
using parser_type = typename std::result_of<Func(value<Parser>)>::type;
using value_type = value<parser_type>;
using result_type = result<value_type>;
return parser(in) >>= [&](success<value<Parser>>&& self) -> result_type {
const range in = self;
if(auto res = func(std::move(self.value))(in)) {
return res;
}
return error(in);
};
};
};
template<class Parser, class Func, class=value<Parser>>
static auto operator>>=(Parser parser, Func func) {
return bind(parser, func);
};
// sequence parser
template<class LHS, class RHS, class=value<LHS>, class=value<RHS>>
static auto operator>>(LHS lhs, RHS rhs) {
return lhs >>= [rhs = std::move(rhs)](auto) { return rhs; };
};
// guarded continuation
template<class Pred>
static auto guard(Pred pred) {
return [pred = std::move(pred)](auto value) {
using value_type = decltype(value);
return [pred, value = std::move(value)](range in) -> result<value_type> {
if(pred(value)) {
return make_success(value, in);
}
return error(in);
};
};
};
// drop continuation
template<class Parser>
static auto drop(Parser parser) {
return [parser = std::move(parser)](auto value) {
return parser >> pure(std::move(value));
};
}
// reference parser
template<class Parser>
static auto ref(const Parser& parser) {
return [&](range in) -> result<value<Parser>> { return parser(in); };
}
// kleen star parser (zero-or-more). note: always succeeds
template<class Parser>
static auto kleene(Parser parser) {
return [parser = std::move(parser)](range in) -> result<std::deque<value<Parser>>> {
std::deque<value<Parser>> values;
while(auto result = parser(in)) {
values.emplace_back(std::move(result.get()->value));
in = *result.get();
}
return make_success(std::move(values), in);
};
};
// one-or-more parser
template<class Parser>
static auto plus(Parser parser) {
return parser >>= [parser](auto first) {
return kleene(parser) >>= [first](auto rest) {
rest.emplace_front(std::move(first));
return pure(rest);
};
};
};
// coproduct parser (alternative). note: rhs is only called if lhs fails
template<class LHS, class RHS>
static auto coproduct(LHS lhs, RHS rhs) {
return [lhs = std::move(lhs), rhs = std::move(rhs)](range in) {
if(auto res = lhs(in)) {
return res;
} else
return rhs(in);
};
};
template<class LHS, class RHS, class=value<LHS>, class=value<RHS>>
static auto operator|(LHS lhs, RHS rhs) {
return coproduct(std::move(lhs), std::move(rhs));
}
// non-empty list with separator
template<class Parser, class Separator>
static auto list(Parser parser, Separator separator) {
return parser >>= [=](auto first) {
return kleene(separator >> parser) >>=
[first = std::move(first)](auto rest) {
rest.emplace_front(first);
return pure(rest);
};
};
};
template<class Parser, class Separator, class=value<Parser>, class=value<Separator>>
static auto operator%(Parser parser, Separator separator) {
return list(std::move(parser), std::move(separator));
}
// skip parser: parse zero-or-more without collecting
template<class Parser>
static auto skip(Parser parser) {
return [parser = std::move(parser)](range in) -> result<unit> {
while(auto res = parser(in)) {
in = *res.get();
}
return make_success(unit{}, in);
};
}
// tokenizer: skip before parsing
template<class Parser, class Skipper>
static auto token(Parser parser, Skipper skipper) {
return skip(skipper) >> parser;
}
// debugparser
template<class Parser>
static auto debug(std::string name, Parser parser,
std::ostream& out = std::clog) {
return [name = std::move(name), parser = std::move(parser), &out](range in) {
out << "> " << name << ": \"";
peek(in, out);
out << "\"\n";
auto res = parser(in);
if(res) {
out << "< " << name << " ok: \"";
peek(*res.get(), out);
out << "\"\n";
} else {
std::clog << "< " << name << " failed\n";
}
return res;
};
}
// longest parse: runs both parsers and keep the longest match. note: lhs result
// is returned in case of a draw.
template<class LHS, class RHS>
static auto longest(LHS lhs, RHS rhs) {
return [lhs = std::move(lhs), rhs = std::move(rhs)](range in) {
auto as_lhs = lhs(in);
auto as_rhs = rhs(in);
if(!as_rhs)
return as_lhs;
if(!as_lhs)
return as_rhs;
if(as_lhs.get()->first >= as_rhs.get()->first) {
return as_lhs;
} else {
return as_rhs;
}
};
};
// fixpoint (result type needs to be given because c++)
template<class T, class Def>
struct fixpoint {
const Def def;
result<T> operator()(parser::range in) const {
return def(*this)(in);
}
};
template<class T, class Def>
static fixpoint<T, Def> fix(Def def) {
return {def};
}
////////////////////////////////////////////////////////////////////////////////
// concrete parsers
static result<const char*> cursor(range in) {
return make_success(in.first, in);
};
// char parser
static result<char> character(range in) {
if(!in) {
return error(in);
}
return make_success(in.get(), in.next());
};
// parse char matching a predicate
template<class Pred>
static auto pred(Pred pred) {
return character >>= guard(pred);
}
static auto pred(int (*pred)(int)) { return character >>= guard(pred); }
// parse a given char
static auto single(char c) {
return pred([c](char x) { return x == c; });
}
// parse a fixed keyword
static auto keyword(std::string value) {
return [value = std::move(value)](range in) -> result<unit> {
if(in.size() < value.size()) {
return error(in);
}
if(value.compare(0, value.size(), in.first, value.size()) == 0) {
return make_success(unit{}, range{in.first + value.size(), in.last});
}
return error(in);
};
}
// parse numbers. note: leading whitespaces (as per std::isspace) are consumed
static result<double> _double(range in) {
if(!in)
return error(in);
char* end;
const double res = std::strtod(in.first, &end);
if(end == in.first)
return error(in);
return make_success(res, range{end, in.last});
}
static result<float> _float(range in) {
if(!in)
return error(in);
char* end;
const float res = std::strtof(in.first, &end);
if(end == in.first)
return error(in);
return make_success(res, range{end, in.last});
}
static result<long> _long(range in) {
if(!in)
return error(in);
char* end;
const long res = std::strtol(in.first, &end, 10);
if(end == in.first)
return error(in);
return make_success(res, range{end, in.last});
}
static result<unsigned long> _unsigned_long(range in) {
if(!in)
return error(in);
char* end;
const unsigned long res = std::strtoul(in.first, &end, 10);
if(end == in.first)
return error(in);
return make_success(res, range{end, in.last});
}
// convenience tokenizer
template<class Parser>
static auto token(Parser parser) {
return skip(pred(std::isspace)) >> parser;
}
// end of stream parser
static result<unit> eos(range in) {
if(in.first == in.last) {
return make_success(unit{}, in);
}
return error(in);
}
////////////////////////////////////////////////////////////////////////////////
template<class Parser>
static value<Parser> run(Parser parser, range in) {
// TODO report line/col
return match(
parser(in),
[=](error err) -> value<Parser> {
std::stringstream ss;
ss << "parse error near \"";
peek(err, ss);
ss << "\"";
throw std::runtime_error(ss.str());
},
[](success<value<Parser>>& ok) { return std::move(ok.value); });
}
static std::string read(std::istream& in) {
return {std::istreambuf_iterator<char>(in), {}};
}
// range TODO put in range?
static std::size_t line(range what, range context) {
assert(what.last <= context.last);
assert(what.first >= context.first);
std::size_t result = 0;
for(const char* it = context.first; it != what.first; ++it) {
if(*it == '\n') {
++result;
}
}
return result;
}
static range grow(range what, range context, std::size_t lines=1) {
assert(what.last <= context.last);
assert(what.first >= context.first);
range result;
{
std::size_t count = 0;
for(auto it = what.first; it >= context.first; --it) {
if(*it == '\n') {
if(++count == lines) {
result.first = it + 1;
}
}
}
if(!count) {
result.first = context.first;
}
}
{
std::size_t count = 0;
for(auto it = what.last; it <= context.last; ++it) {
if(*it == '\n') {
if(++count == lines) {
result.last = it;
}
}
}
if(!count) {
result.first = context.last;
}
}
return result;
}
} // namespace parser
#endif