Re: boost::spirit and boost in general for c++ people.

um. did you read the code? I -did- use the spirit parser. but you still need an AST, which Spirit will create for you.

On 4/7/2011 8:07 AM, Ken Perry wrote:
Oh for the calculator you really should use the boost spirit parser so you
don't have to write your own.

Ken

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Littlefield,
Tyler
Sent: Thursday, April 07, 2011 9:09 AM
To: programmingblind@xxxxxxxxxxxxx
Subject: boost::spirit and boost in general for c++ people.

hello all:
Recently I got into using boost a bit and started finding uses for it
all over the place. I would like to encourage those who haven't yet and
use c++ to check it out; it is quite powerful and can eas some of your
work and provide really cool features along the way. For example:
boost::function lets you take callbacks in multiple forms; boost::bind
will let you bind a functor to it's arguments and pass that as your
callback, which means you can bind to a static member function, a member
function (and pass the object with boost::ref), a global function and
you can also use boost::lambda.
There are many more utilities out there; I highly recommend checking out
boost::asio, boost::fusion, boost::function and boost::bind.
In the spirit of convincing you all, I wrote a small calculator program
that does single operations (1+3, 3*5), etc and returns the result.
My next step is to split up my parsing into different rulesets and then
work on generating an AST so that I can handle larger more complex
calculations.
/*
A simple calculator, supports multiplication, division, addition and
subtraction.
*/
#include<boost/spirit/include/qi.hpp>
#include<boost/spirit/include/phoenix_core.hpp>
#include<boost/spirit/include/phoenix_operator.hpp>
#include<boost/spirit/include/phoenix_operator.hpp>
#include<iostream>
#include<string>
#include<boost/fusion/include/adapt_struct.hpp>
#include<boost/fusion/container/vector.hpp>
#include<boost/fusion/container/vector/convert.hpp>
#include<boost/fusion/include/io.hpp>

namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;

struct calculation
{
    int a, b;
    char op;
};
BOOST_FUSION_ADAPT_STRUCT(calculation, (int, a) (char, op) (int, b) )

template<typename iterator>
class CParser:public qi::grammar<iterator, calculation(),
qi::ascii::space_type>
{
    qi::rule<iterator, calculation(), qi::ascii::space_type>  crule;
public:
    CParser():CParser::base_type(crule)
    {
      using qi::ascii::char_;
      using qi::int_;

      crule %= (int_>>
                (char_('+')|char_('-')|char_('*')|char_('/'))>>
                int_);
    }
};

int main()
{
    CParser<std::string::iterator>  p;
    std::string str;
    calculation result;

    std::cout<<  "Enter your calculation>";
getline(std::cin, str);

    bool r = phrase_parse(str.begin(), str.end(), p, qi::ascii::space,
result);
    if (r)
      {
        std::cout<<  "a: "<<  result.a<<  " b: "<<  result.b<<  " op: "
<<  result.op<<  std::endl;
        switch(result.op)
          {
          case '+':
            std::cout<<  "Result: "<<  (result.a + result.b)<<  std::endl;
            break;
          case '-':
            std::cout<<  "result: "<<  (result.a - result.b)<<  std::endl;
            break;
          case '*':
            std::cout<<  "Result: "<<  (result.a * result.b)<<  std::endl;
            break;
          case '/':
            if (result.a == 0)
              {
                std::cout<<  "Division by zero error."<<  std::endl;
                break;
              }
            std::cout<<  "result: "<<  (result.a / result.b)<<  std::endl;
            break;
          default:
            std::cout<<  "Invalid operation."<<  std::endl;
          }
      }
    else
      {
        std::cout<<  "Invalid input."<<  std::endl;
      }

    return 0;
}



--

Thanks,
Ty

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