我正在尝试使用 Boost.Spirit (V. 2.5) 库来创建一个迷你计算器。我要实现的功能： - 基本微积分（+、-、/、*），有效 - 一些函数（如 min、max），也有效 - 声明/分配双变量，问题出在......我添加“[vars.add]”我得到编译错误（模板参数不明确）。我试过“add（char_（_1）”，“add（_1）”，......但似乎没有任何效果。我显然错过了一些东西（实际上不理解一些东西）。如果有人可以帮助我，我会我非常感激！
这是来源：
#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;
}
我想做一些事情，例如：
var i,j
i = 1
j = max(2*(i+1),5)