C++ String Find and Replace

[Muhasaresa]

:D Hello everyone,

I am making a console app in MSVS 2008. I was wondering if it is possible to find part of a string and replace it with the following letters:

"128." = "a"
"70." = "b"
"88." = "c"

So if I had "128.88.70.128.70." it would go to "acbab". I got this far from a previous forum with the help of ZED0815:

#include <iostream>
#include <string>
#include <Windows.h> 


using namespace std;

int main ()
{    
  string str ("128.88.70.128.70.");
  string searchFora ("128.");    
  string replaceBya ("a");

 string searchForb ("70.");
  string replaceByb ("b");

 string searchForc ("88.");
  string replaceByc ("c");     

  
  size_t found;
  
  
  
  found = str.find( searchFora );
  while (found!=string::npos){
    str.replace( found, sizeof( searchFora ), replaceBya );
    found = str.find( searchFora );
  };
  
    found = str.find( searchForb );
  while (found!=string::npos){
    str.replace( found, sizeof( searchForb ), replaceByb );
    found = str.find( searchForb );
  };
  
    found = str.find( searchForc );
  while (found!=string::npos){
    str.replace( found, sizeof( searchForc ), replaceByc );
    found = str.find( searchForc );
  };

  cout << str << endl;
  
  cin.clear();
cin.ignore(255, '\n');
cin.get();
  
  
  return 0;
}

It output only the first 3 character "acb". Do I have to do something to the size_t found; to get it working?

Thanks for any help,

Muhasaresa

[Galik]

You can not use sizeof() to get the length of a std::string. You must use either std::string::length() or std::string::size()

str.replace( found, sizeof( searchFora ), replaceBya ); // this is wrong

str.replace(found, searchFora.size(), replaceBya); // try this 

[Duthomhas]

Heh heh heh...

Such a function has long existed in Tcl
http://www.tcl.tk/man/tcl8.5/TclCmd/string.htm#M39

Here's my C++ version:

#pragma once
#ifndef DUTHOMHAS_STRING_MAP_HPP
#define DUTHOMHAS_STRING_MAP_HPP

#include <algorithm>
#include <iterator>
#include <string>

template <typename Iterator>
std::string string_map( const std::string& s, Iterator begin, Iterator end )
  {
  std::string result;

  for (size_t n = 0; n < s.length(); )
    {
    for (Iterator key = begin; key != end; std::advance( key, 2 ))
      {
      if (s.find( *key, n ) == n)
        {
        Iterator value = key;
        std::advance( value, 1 );
        result.append( *value );
        n += std::string( *key ).length() - 1;
        goto next;
        }
      }
    result += s[ n ];
    next: ++n;
    }

  return result;
  }

template <typename String, size_t N>
inline
std::string string_map( const std::string& s, String (&mapping)[ N ] )
  {
  return string_map( s, mapping, mapping + N );
  }

template <typename Container>
inline
std::string string_map( const std::string& s, const Container& mapping )
  {
  return string_map( s, mapping.begin(), mapping.end() );
  }

#endif 

This was my first pass at it -- I'm sure I could improve it some. And yes, that goto was intensional -- it demonstrates valid use.

[flame on] Anyone who wants to correct me has to do so without getting flaggy or involving other overhead.

Hint: It can be done easily enough. If no one does I will before long.

[shacktar]

I'm not flaming. I just saw a challenge. For the record, it makes sense to use goto instead of trying to break awkwardly out of a heavily nested structure.

for (size_t n = 0; n < s.length(); ++n)
  {
  result += s[ n ];
  for (Iterator key = begin; key != end; std::advance( key, 2 ))
    {
    if (s.find( *key, n ) == n)
      {
      Iterator value = key;
      std::advance( value, 1 );
      result.replace( result.length() - 1, 1, *value );
      n += std::string( *key ).length() - 1;
      break;
      }
    }
  }

Edit: moved ++n to within the for loop header

[Galik]

I wrote a similar function to replace string patterns from an input stream to an output stream. Its fairly involved because I tried to make it efficient and so it uses a circular buffer to store the matched portion of the input stream. However, I have extracted and converted the string replace portion to work on strings rather than streams. I manage to avoid a goto by putting the key match test in the for loop that tries each key:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

#include <string> #include <vector> #include <iostream> typedef std::pair<std::string, std::string> str_pair; typedef std::vector<str_pair> str_map; typedef str_map::iterator map_iter; typedef str_map::const_iterator map_citer; std::string map_copy(const str_map& m, const std::string& str) { std::string out; map_citer i; for(size_t pos = 0; pos < str.size(); ++pos) { for(i = m.begin(); i != m.end() && str.find(i->first, pos) != pos; ++i); if(i != m.end()) { out.append(i->second); pos += i->first.length() - 1; continue; } out.append(1, str[pos]); } return out; } int main() { str_map map1; str_map map2; map1.push_back(str_pair("abc", "1")); map1.push_back(str_pair("ab", "2")); map1.push_back(str_pair("a", "3")); map1.push_back(str_pair("1", "0")); map2.push_back(str_pair("1", "0")); map2.push_back(str_pair("ab", "2")); map2.push_back(str_pair("a", "3")); map2.push_back(str_pair("abc", "1")); std::cout << map_copy(map1, "1abcaababcabababc") << '\n'; std::cout << map_copy(map2, "1abcaababcabababc") << '\n'; return 0; }

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[Muhasaresa]

Thanks everyone for your help :D

Muhasaresa