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Re: Conversion of a number from string to vector<int>

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Pete Becker ha scritto:
> On 2011-06-19 07:13:27 -0400, Anonymous said:
> Use an unsigned int, and represent the values in base UINT_MAX + 1. That 
> uses all the bits.
> 
> To convert a text string, just use the obvious <g> approach:
> 
> set the current value to 0
> set the current position in the string to the leftmost character
> while the character at the current position is in '0'..'9'
>     multiply the current value by 10
>     add the value represented by the digit to the current value
>     move the current position one place to the right
> 
> Try it with pencil and paper a few times to get the feel of it.

I don't think the algorithm you are describing can use all the bits 
available. As I said in my previous thread, the algorithm you are 
talking about, which is similar to the one I wrote initially, can 
represent the number in base B, where int B is a power of 10. Since the 
base it's a power of 10, it cannot profit by all the available bits in 
the integer. In other words:

10^std::numeric_limits<unsigned int>::digits10 -1 < 
2^std::numeric_limits<unsigned int>::digits - 1,

on my architecture:
10^9-1 < 2^32-1,
999999999 < 4294967295,

which is about two bits lost.

Below is the actual algorithm again:

#include <vector>
#include <limits>
#include <string>

typedef unsigned long Bitset; // the more is sizeof() , the more math 
ops are fast
static const int DGTS = std::numeric_limits<Bitset>::digits10;

std::vector<Bitset> f(const char* p = 0) {
     std::vector<Bitset> module;
     size_t l = std::string(p).length();
     for (size_t i = 0; i < l;) {
         Bitset x = 0, f = 1;
         for (int j = 0; j < DGTS && i < l; j++, i++, f *= 10)
             x += (p[l - i - 1] - '0') * f;
         module.push_back(x);
     }
     return module;
}

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Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-18 19:59 +0200
  Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-18 20:08 +0100
    Re: Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-18 23:55 +0200
      Re: Conversion of a number from string to vector<int> Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-18 18:26 -0400
    Re: Conversion of a number from string to vector<int> Juha Nieminen <nospam@thanks.invalid> - 2011-06-19 06:15 +0000
      Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-19 08:02 +0100
        Re: Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-19 12:19 +0200
          Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-19 16:07 +0100
            Re: Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-19 17:50 +0200
            Re: Conversion of a number from string to vector<int> Juha Nieminen <nospam@thanks.invalid> - 2011-06-20 06:12 +0000
              Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 09:57 +0100
        Re: Conversion of a number from string to vector<int> Juha Nieminen <nospam@thanks.invalid> - 2011-06-20 06:09 +0000
          Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 09:48 +0100
          Re: Conversion of a number from string to vector<int> Ian Collins <ian-news@hotmail.com> - 2011-06-20 20:59 +1200
            Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 10:17 +0100
              Re: Conversion of a number from string to vector<int> Lasse Reichstein Nielsen <lrn.unread@gmail.com> - 2011-06-20 22:47 +0200
                Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 22:05 +0100
  Re: Conversion of a number from string to vector<int> Ian Collins <ian-news@hotmail.com> - 2011-06-19 08:35 +1200
  Re: Conversion of a number from string to vector<int> Juha Nieminen <nospam@thanks.invalid> - 2011-06-19 06:23 +0000
    Re: Conversion of a number from string to vector<int> Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-06-19 12:14 +0200
    Re: Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-19 13:13 +0200
      Re: Conversion of a number from string to vector<int> Pete Becker <pete@versatilecoding.com> - 2011-06-19 11:42 -0400
        Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-19 20:54 +0100
        Re: Conversion of a number from string to vector<int> Anonymous <anonymous@no.net> - 2011-06-19 23:06 +0200
          Re: Conversion of a number from string to vector<int> Pete Becker <pete@versatilecoding.com> - 2011-06-19 17:18 -0400
          Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 00:11 +0100
            Re: Conversion of a number from string to vector<int> "Paul" <pchristor@yahoo.co.uk> - 2011-06-20 00:32 +0100
    Re: Conversion of a number from string to vector<int> Juha Nieminen <nospam@thanks.invalid> - 2011-06-20 06:18 +0000
  Re: Conversion of a number from string to vector<int> Sam <sam@email-scan.com> - 2011-06-21 06:05 -0500

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