95 lines
2.5 KiB
C++
95 lines
2.5 KiB
C++
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/**
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* @file mix_cc/matheval/matheval.hpp
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* @brief 最终头文件
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* @author Cat (null.null.null@qq.com)
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* @version 0.1
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* @date 2021-09-17
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*
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* Copyright: Baosight Co. Ltd.
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* DO NOT COPY/USE WITHOUT PERMISSION
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*
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*/
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#pragma once
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#include <map>
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#include <memory>
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#include <string>
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namespace mix_cc {
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namespace matheval {
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/// @brief Parse a mathematical expression
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///
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/// This can parse and evaluate a mathematical expression for a given
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/// symbol table using Boost.Spirit X3. The templates of Boost.Spirit
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/// are very expensive to parse and instantiate, which is why we hide
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/// it behind an opaque pointer.
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///
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/// The drawback of this approach is that calls can no longer be
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/// inlined and because the pointer crosses translation unit
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/// boundaries, dereferencing it can also not be optimized out at
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/// compile time. We have to rely entirely on link-time optimization
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/// which might be not as good.
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///
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/// The pointer to the implementation is a std::unique_ptr which makes
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/// the class not copyable but only moveable. Copying shouldn't be
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/// required but is easy to implement.
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class Parser {
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class impl;
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std::unique_ptr<impl> pimpl;
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public:
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/// @brief Constructor
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Parser();
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/// @brief Destructor
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~Parser();
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/// @brief Parse the mathematical expression into an abstract syntax tree
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///
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/// @param[in] expr The expression given as a std::string
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void parse(std::string const& expr);
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/// @brief Perform constant folding onto the abstract syntax tree
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void optimize();
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/// @brief Evaluate the abstract syntax tree for a given symbol table
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///
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/// @param[in] st The symbol table
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double evaluate(std::map<std::string, double> const& st = {});
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};
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/// @brief Parse a mathematical expression
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class Expression {
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class impl;
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std::unique_ptr<impl> pimpl;
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public:
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///@brief build math expression
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Expression(std::string const& math_expr, std::map<std::string, double>* const);
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~Expression();
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///@brief evaluate the value of input expression
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double evaluate();
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};
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/// @brief Convenience function
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///
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/// This function builds the grammar, parses the iterator to an AST,
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/// evaluates it, and returns the result.
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///
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/// @param[in] expr mathematical expression
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/// @param[in] st the symbol table for variables
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inline double parse(std::string const& expr,
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std::map<std::string, double> const& st = {}) {
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Parser parser;
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parser.parse(expr);
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return parser.evaluate(st);
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}
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} // namespace matheval
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} // namespace mix_cc
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