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

I have always hated spirit for its um not nice way of doing things. I
actually like bison grammer over it.

Ken

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Sina Bahram
Sent: Thursday, April 07, 2011 11:22 AM
To: programmingblind@xxxxxxxxxxxxx
Subject: RE: boost::spirit and boost in general for c++ people.

Good god, this is ugly.

Seriously, you guys find that code easy to read?

Take care,
Sina

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Ken Perry
Sent: Thursday, April 07, 2011 10:07 AM
To: programmingblind@xxxxxxxxxxxxx
Subject: RE: boost::spirit and boost in general for c++ people.

Snicker welcome to the future... Hmm how many times have I told you to use
it and you told me no???

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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