numbers.cpp

Boost provides free peer-reviewed portable C++ source libraries. We emphasize libraries that work

///////////////////////////////////////////////////////////////////////////////
// numbers.cpp
//
//  Copyright 2008 David Jenkins. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#if defined(_MSC_VER)
//disbale warning C4996: 'std::xxx' was declared deprecated
# pragma warning(disable:4996)
#endif

#include <iostream>
#include <string>
#include <map>
#include <boost/assign/list_of.hpp> // for 'map_list_of()'
#include <boost/xpressive/xpressive.hpp>
#include <boost/xpressive/regex_actions.hpp>

///////////////////////////////////////////////////////////////////////////////
// Match all named numbers in a string and return their integer values
//
// For example, given the input string:
//      "one two sixty three thousand ninety five eleven"
// the program will output:
//      "one = 1"
//      "two = 2"
//      "sixty three thousand ninety five = 63095"
//      "eleven = 11"

void example1()
{
    using namespace boost::xpressive;
    using namespace boost::assign;

    // initialize the maps for named numbers
    std::map< std::string, int > ones_map =
        map_list_of("one",1)("two",2)("three",3)("four",4)("five",5)
        ("six",6)("seven",7)("eight",8)("nine",9);

    std::map< std::string, int > teens_map =
        map_list_of("ten",10)("eleven",11)("twelve",12)("thirteen",13)
        ("fourteen",14)("fifteen",15)("sixteen",16)("seventeen",17)
        ("eighteen",18)("nineteen",19);

    std::map< std::string, int > tens_map =
        map_list_of("twenty",20)("thirty",30)("fourty",40)
        ("fifty",50)("sixty",60)("seventy",70)("eighty",80)("ninety",90);

    std::map< std::string, int > specials_map =
        map_list_of("zero",0)("dozen",12)("score",20);

    // n is the integer result
    local<long> n(0);
    // temp stores intermediate values
    local<long> temp(0);

    // initialize the regular expressions for named numbers
    sregex tens_rx =
        // use skip directive to skip whitespace between words
        skip(_s)
        (
            ( a3 = teens_map )
            |
            ( a2 = tens_map ) >> !( a1 = ones_map )
            |
            ( a1 = ones_map )
        )
        [ n += (a3|0) + (a2|0) + (a1|0) ];

    sregex hundreds_rx =
        skip(_s)
        (
            tens_rx >>
            !(
                as_xpr("hundred")  [ n *= 100 ]
                >> !tens_rx
             )
        )
        ;

    sregex specials_rx =    // regex for special number names like dozen
        skip(_s)
        (
            // Note: this uses two attribues, a1 and a2, and it uses
            // a default attribute value of 1 for a1.
            ( !( a1 = ones_map ) >> ( a2 = specials_map ) )
                [ n = (a1|1) * a2 ]
            >> !( "and" >> tens_rx )
        )
        ;

    sregex number_rx =
        bow
        >>
        skip(_s|punct)
        (
            specials_rx // special numbers
            |
            (   // normal numbers
                !( hundreds_rx >> "million" ) [ temp += n * 1000000, n = 0 ]
                >>
                !( hundreds_rx >> "thousand" ) [ temp += n * 1000, n = 0 ]
                >>
                !hundreds_rx
            )
            [n += temp, temp = 0 ]
        );

    // this is the input string
    std::string str( "one two three eighteen twenty two "
        "nine hundred ninety nine twelve "
        "eight hundred sixty three thousand ninety five "
        "sixty five hundred ten "
        "two million eight hundred sixty three thousand ninety five "
        "zero sixty five hundred thousand "
        "extra stuff "
        "two dozen "
        "four score and seven");

    // the MATCHING results of iterating through the string are:
    //      one  = 1
    //      two  = 2
    //      three  = 3
    //      eighteen  = 18
    //      twenty two  = 22
    //      nine hundred ninety nine  = 999
    //      twelve  = 12
    //      eight hundred sixty three thousand ninety five  = 863095
    //      sixty five hundred ten  = 6510
    //      two million eight hundred sixty three thousand ninety five  = 2863095
    //      zero = 0
    //      sixty five hundred thousand = 6500000
    //      two dozen = 24
    //      four score and seven = 87
    sregex_token_iterator cur( str.begin(), str.end(), number_rx );
    sregex_token_iterator end;

    for( ; cur != end; ++cur )
    {
        if ((*cur).length() > 0)
            std::cout << *cur << " = " << n.get() << '\n';
        n.get() = 0;
    }
    std::cout << '\n';
    // the NON-MATCHING results of iterating through the string are:
    //      extra = unmatched
    //      stuff = unmatched
    sregex_token_iterator cur2( str.begin(), str.end(), number_rx, -1 );
    for( ; cur2 != end; ++cur2 )
    {
        if ((*cur2).length() > 0)
            std::cout << *cur2 << " = unmatched" << '\n';
    }
}

///////////////////////////////////////////////////////////////////////////////
// main
int main()
{
    std::cout << "\n\nExample 1:\n\n";
    example1();

    std::cout << "\n\n" << std::flush;

    return 0;
}