我正在尝试使用Boost.Spirit（V. 2.5）库来创建一个迷你计算器。我想要实现的功能： - 基本微积分（+， - ，/，*），有效 - 一些功能（如min，max），也可以 - 声明/分配双变量，并且存在问题......当我添加“[vars.add]”时，我得到编译错误（模板参数模糊）。 我试过“添加（char _（_ 1）”，“添加（_1）”，......似乎没什么用。我显然缺少一些东西（实际上并没有理解）。如果有人可以帮助我，我会我非常感激！
以下是来源：
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/home/phoenix/statement/if.hpp>
#include <boost/spirit/home/phoenix/bind/bind_function.hpp>
#include <iostream>
#include <string>
namespace client
{
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phx = boost::phoenix;
struct vars_ : qi::symbols<char, double> {
vars_() {
add("ans" , 0);
}
} vars;
template <typename Iterator>
struct parser : qi::grammar<Iterator, double()>
{
parser() : parser::base_type(function)
{
using qi::eps;
using qi::lit;
using qi::_val;
using qi::_1;
using ascii::char_;
using qi::double_;
using qi::string;
using qi::lexeme;
using boost::phoenix::if_;
using qi::alpha;
using qi::alnum;
MAX = lexeme[string("max") | string("MAX")]; //define max symbol
MIN = lexeme[string("min") | string("MIN")]; //define min symbol
D = lexeme[string("d") | string("D")]; //define distance symbol
ANS = lexeme[string("ans") | string("ANS")]; //not working yet
function =
expression [_val = _1]
| declaration
| assignment
| ( MAX >> "(" >> function [_val = _1] >>
+(',' >> function [if_(_1 > _val)[_val = _1]]) >> ')') // call : max(function,...)
| ( MIN >> "(" >> function [_val = _1] >>
+(',' >> function [if_(_1 < _val)[_val = _1]]) >> ')') // call : min(function,...)
| ( D >> "(" >> (function >> ',' >> function) >> ')'); // call : d(point1,point2) not implemented yet
expression =
term [_val = _1]
>> *( ('+' >> term [_val += _1])
| ('-' >> term [_val -= _1]));
term =
factor [_val = _1]
>> *( ('*' >> factor [_val *= _1])
| ('/' >> factor [_val /= _1]));
factor =
double_ [_val = _1]
| (vars [_val += _1] )
| '(' >> expression [_val = _1] >> ')'
| ('-' >> factor [_val = -_1])
| ('+' >> factor [_val = _1])
| declaration;
;
assignment =
vars >> '=' >> function;
var_decl =
lexeme [ qi::raw [ ( alpha >> *( alnum | '_' ) ) - vars ] ] //[ phx::bind(vars.add, _1) ]
;
declaration =
"var " >> var_decl >> *( ',' >> var_decl );
}
qi::rule<Iterator, double()> MAX, MIN, D, ANS, expression, term, factor,
function, assignment, var_decl, declaration;
};
}
///////////////////////////////////////////////////////////////////////////////
// Main program
///////////////////////////////////////////////////////////////////////////////
int main()
{
std::cout << "**********************************************************" << std::endl;
std::cout << "* *" << std::endl;
std::cout << "* Command interface for VideoTraction4 *" << std::endl;
std::cout << "* *" << std::endl;
std::cout << "**********************************************************" << std::endl << std::endl;
std::cout << "Type an expression...or [q or Q] to quit" << std::endl << std::endl;
typedef std::string::const_iterator iterator_type;
typedef client::parser<iterator_type> parser;
parser _parser; // Our grammar
std::string str;
double result;
while (std::getline(std::cin, str))
{
if (str.empty() || str[0] == 'q' || str[0] == 'Q')
break;
std::string::const_iterator iter = str.begin();
std::string::const_iterator end = str.end();
bool r = parse(iter, end, _parser, result);
if (r && iter == end)
{
std::cout << "-------------------------\n";
std::cout << "Parsing succeeded\n";
std::cout << "result = " << result << std::endl;
std::cout << "-------------------------\n";
client::vars.remove("ans");
client::vars.add("ans",result);
}
else
{
std::string rest(iter, end);
std::cout << "-------------------------\n";
std::cout << "Parsing failed\n";
std::cout << "stopped at: \": " << rest << "\"\n";
std::cout << "-------------------------\n";
}
}
std::cout << "Bye... :-) \n\n";
return 0;
}
我想做的事情如下：
var i,j
i = 1
j = max(2*(i+1),5)
答案 0 :(得分：2)
嗯，我从未在Semantic Actions中直接添加符号（我更喜欢构建AST，然后遍历那些）。
你这样写的事实和SSCCE的缺席让我傻了一下。事实证明，我应该忽略间接的“证据”并直接进行文档+胜利：
var_decl =
qi::as_string [ lexeme [ ( ( alpha >> *( alnum | '_' ) ) - vars ) ] ]
[ phx::bind(vars.add, _1) ];
或
var_decl =
lexeme [ qi::raw [ ( alpha >> *( alnum | '_' ) ) - vars ] ]
[ phx::bind(vars.add, _1) ];
和一些类似的咒语将适用
编辑以下是在MSVC 2010上编译的完整源代码，使用boost 1.47：
输出：
T:\>cl /EHsc /I "c:\Program Files (x86)\boost\boost_1_47" test.cpp
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 for 80x86
Copyright (C) Microsoft Corporation. All rights reserved.
test.cpp
Microsoft (R) Incremental Linker Version 10.00.30319.01
Copyright (C) Microsoft Corporation. All rights reserved.
/out:test.exe
test.obj
T:\>.\test.exe
**********************************************************
* *
* Command interface for VideoTraction4 *
* *
**********************************************************
Type an expression...or [q or Q] to quit
3*4+7
-------------------------
Parsing succeeded
result = 19
-------------------------
稍微不相关的说明：看起来很有趣 - var_decl规则的公开属性似乎是char？
您可能想要阅读自动规则和%=运算符;如果没有％=，语义操作的存在将抑制所有自动属性传播。如果不存在所需的自定义点，这将非常有用。如上所述，exposed属性将始终为unassigned-to。