mirror of
https://github.com/matrix-construct/construct
synced 2024-12-28 08:24:08 +01:00
79 lines
2.6 KiB
C++
79 lines
2.6 KiB
C++
// The Construct
|
|
//
|
|
// Copyright (C) The Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2022 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_SPIRIT_EXPR_H
|
|
|
|
namespace ircd::spirit
|
|
{
|
|
template<class T>
|
|
struct [[clang::nodebug]] expr;
|
|
}
|
|
|
|
/// Expression storage wrapper. This could also be called `named_expression`.
|
|
/// This allows spirit expressions to be instantiated in global variables
|
|
/// along with a simple name string (and potentially other metadata). Why not
|
|
/// just use a rule, you say? The rule templates perform type erasure on the
|
|
/// original expression by constructing function objects which are prototyped
|
|
/// to the rule such that the expression is lost behind a call. Compilers are
|
|
/// able to optimize this like it was never even there, but only when all rules
|
|
/// are constructed in a local stack frame. **Clang is unable to compose rules
|
|
/// defined at global scope without indirect calls**.
|
|
///
|
|
/// Declarations of this object are blessed with C++17 template deduction. At
|
|
/// global scope, compose expressions first before constructing a single rule
|
|
/// right before parsing. !!! Do not allow global scope rules to refer to each
|
|
/// other, even at function scope. !!! Do not allow exprs to refer to rules,
|
|
/// ever. !!! Only allow global scope rules to refer to exprs, and exprs to
|
|
/// other exprs.
|
|
///
|
|
/// Rules constructed at function scope usually generate fully inline parsers.
|
|
/// Rules constructed at global scope usually generate parsers behind a direct
|
|
/// call. Everything else generates a soup of handler functions behind a web
|
|
/// of indirect calls.
|
|
///
|
|
template<class T>
|
|
struct [[gnu::visibility("internal"), clang::internal_linkage]]
|
|
ircd::spirit::expr
|
|
:boost::proto::result_of::deep_copy<T>::type
|
|
{
|
|
const char *const &name;
|
|
|
|
constexpr expr(T &&, const char *const &name);
|
|
constexpr expr(const T &, const char *const &name);
|
|
};
|
|
|
|
template<class T>
|
|
constexpr
|
|
ircd::spirit::expr<T>::expr(const T &e,
|
|
const char *const &name)
|
|
:boost::proto::result_of::deep_copy<T>::type
|
|
{
|
|
boost::proto::deep_copy(e)
|
|
}
|
|
,name
|
|
{
|
|
name
|
|
}
|
|
{}
|
|
|
|
template<class T>
|
|
constexpr
|
|
ircd::spirit::expr<T>::expr(T &&e,
|
|
const char *const &name)
|
|
:boost::proto::result_of::deep_copy<T>::type
|
|
{
|
|
boost::proto::deep_copy(std::move(e))
|
|
}
|
|
,name
|
|
{
|
|
name
|
|
}
|
|
{}
|