strlwr() and delimiter removal

Quote:

---

20 C:\Dev-Cpp\project333 misc\stringtolowercvc.cpp cannot convert `std::string' to `char*' for argument `1' to `char* strlwr(char*)'

---

but all i want to do is convert the entire string to lower case.

Code:

---

  string s;
  while(getline(in, s )) { // Discards newline char
  out << strlwr(s) ;
} // end while

---

also tried

Code:

---

    string s;
    while(getline(in, strlwr(s) ) ) {
    out << s ;
    }

---

same error but but but but it work in c. included are iostream string even tried cstring. fstream for file rw.

after doing several searchs i found transform() i would like to stick with strlwr() that i know for now. read through thinking in cpp vol 1. looking for some type of clue to get it working. even tried strlwr(&s) nope.

delimiter prob

Quote:

---

25 C:\Dev-Cpp\project333 misc\stringuntokin.cpp `get' undeclared (first use this function)
29 C:\Dev-Cpp\project333 misc\stringuntokin.cpp no match for 'operator!=' in '(&words)->std::vector<_Tp, _Alloc>::operator[] [with _Tp = std::string, _Alloc = std::allocator<std::string>](((unsigned int)i)) != '.''
29 C:\Dev-Cpp\project333 misc\stringuntokin.cpp no match for 'operator!=' in '(&words)->std::vector<_Tp, _Alloc>::operator[] [with _Tp = std::string, _Alloc = std::allocator<std::string>](((unsigned int)i)) != ',''

---

yes same error twice

Code:

---

int main() {
  vector<string> words;
 ifstream in(...
ofstream out(...
string word;
    // string s;
  //while(getline(in, s)) // Discards newline char
    //out << s ;          // outline
 
  while(get(in , word) )
    words.push_back(word);
  for(int i = 0; i < words.size(); i++) {
    cout << words[i] ; //endl removed
    while(words[i] != '.' | words[i] != ',' )  out << words[i] ;
    }

---

try change getline() to get(). prob is with while delimiter removal.

Well as of your first function, strlwr() is looking for a const char *, you are supplying a std::string so the quick fix for this is to edit the call to strlwr() like so:

Code:

---

strlwr(s.c_str());

---

Not sure about the rest...

Quote:

---

Originally Posted by kryptkat

after doing several searchs i found transform() i would like to stick with strlwr() that i know for now. read through thinking in cpp vol 1. looking for some type of clue to get it working. even tried strlwr(&s) nope.

---

The problem is that strlwr(), which is not in the C++ standard library, changes the string. As such, jeffcobb's suggestion does not work.

So, you have a few choices: you could allocate space for a null terminated string, copy over the contents of your std::string, and only then apply strlwr(), but then you will be stuck with a null terminated string whose allocated memory needs to be managed manually.

Alternatively, you could pass &s[0] as the argument, but it is not guaranteed to work at this point of time, though it most likely will (but you should push_back() a null character before using it in this way). You can avoid this uncertainty by using a std::vector<char> and passing &v[0] instead, where v is the vector with enough space to store the null terminated string... but frankly you are better off learning how to use transform().

Quote:

---

Originally Posted by laserlight

The problem is that strlwr(), which is not in the C++ standard library, changes the string. As such, jeffcobb's suggestion does not work.
.

---

My mistake, just looked it up, thought it did take a const char * but nope I was wrong. Just checked some old code, I did it once like so:

Code:

---

string myStrLwr(string in)
{
  string strOut = "";
  for(unsigned pos = 0; pos < in.size(); pos++)
  {
      char c = tolower(in.at(pos));
      strOut.push_back(c);
  }
  return strOut;

}

---

Sorry for the confusion...

Jeff

Note: this *does* work; just recompiled and tested myself ^__^

Ah, but then you might as well use std::transform, e.g.,

Code:

---

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), ::tolower);
    return in;
}

---

Quote:

---

Originally Posted by laserlight

Ah, but then you might as well use std::transform, e.g.,

Code:

---

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), ::tolower);
    return in;
}

---

---

Yep might as well. YAWTSAC (Yet Another Way To Skin A Cat)...I never said this was the only way, just what I had written some time ago that worked...

using transform() what about the delimiter removal ? how to use transform to remove delimiters ?

Code:

---

  while(words[i] != '.' | words[i] != ',' )  out << words[i] ;

---

when i tried to use "char q[] = "test string"; " in a class i got can not covert const string. so put it in main() also tried file read. i know the prob is std::string is not char *s or not pointer to char. is not string. transform requires vector ? or algorithm ? for include. do not understand why transform need begin twice ?

lazerlight
when return in is that in in memory or does it write back to file or second file like

Code:

---

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), ::tolower);
    return in;
}
    out <<  in // filetwo.txt

---

thank you both

Quote:

---

YAWTSAC (Yet Another Way To Skin A Cat)

---

<shudders>

Quote:

---

Originally Posted by kryptkat

using transform() what about the delimiter removal ? how to use transform to remove delimiters ?

---

You need to elaborate on what exactly is this delimiter removal about.

Quote:

---

Originally Posted by kryptkat

transform requires vector ? or algorithm ? for include.

---

<algorithm> is the correct header.

Quote:

---

Originally Posted by kryptkat

do not understand why transform need begin twice ?

---

In my example, I am applying transform to the elements of the string, and then assigning the result to those same elements.

Quote:

---

Originally Posted by kryptkat

when return in is that in in memory or does it write back to file or second file like

---

jeffcobb's myStrLwr example is a function that takes a std::string argument by value and returns a std::string object. It has nothing to do with files. Personally, I would have taken the argument by non-const reference and modified it as demonstrated in my example. In such a case, the return type can be void.

Quote:

---

19 C:\Dev-Cpp\project333 misc\stringtolowercase.cpp a function-definition is not allowed here before '{' token

---

this is the error i got when i tried

Code:

---

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), ::tolower);
    return in;
}

---

i was writing to files my bad. i put that in main ().

Quote:

---

Originally Posted by kryptkat

i put that in main ().

---

It is a function definition, and functions cannot be defined within other functions.

Quote:

---

Originally Posted by kryptkat

this is the error i got when i tried

Code:

---

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), ::tolower);
    return in;
}

---

i was writing to files my bad. i put that in main ().

---

I've seen problems like that before, relating to the fact that tolower() is a macro. It's not SUPPOSED to be a macro if you include <cctype> instead of <ctype.h>, but some library implementations are broken, go figure. Try this:

Code:

---

char MyToLower( char ch )
{
    return tolower( ch );
}

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), MyToLower);
    return in;
}

---

i realized it was a function definition after i got the error.

Code:

---

/* stringtolowercase.cpp */

#include <iostream>
#include <string>
#include <fstream>
#include <algorithm>
#include <cctype>

using namespace std;

char MyToLower( char ch )
{
    return tolower( ch );
}

string myStrLwr(string in)
{
    transform(in.begin(), in.end(), in.begin(), MyToLower);
    return in;
}

int main() {
    ifstream in("filetext.txt");
    ofstream out("filetextoutlowercase.txt");

//    string s;
// while(getline(in, s)) // Discards newline char
//    out << s << "\n"; // ... must add it back
 
// want to convert entire file to lower case get stuck here

//


out << fget( MyToLower(in) )  ;

}

---

yikes.

Quote:

---

Originally Posted by kryptkat

// want to convert entire file to lower case get stuck here

---

In the simple case it's the same code as lowercasing the string, just with different iterators.

Code:

---

#include <iterator>

int main() {
    ifstream in("filetext.txt");
    ofstream out("filetextoutlowercase.txt");

    if(!(in && out))
    {
        // handle error
    }

    std::transform(
        std::istreambuf_iterator<char>(in),
        std::istreambuf_iterator<char>(),
        std::ostreambuf_iterator<char>(out),
        MyToLower
    );
    // 'out' now contains a lowercased version of in

---

If the file contains wide chars then change the type of the iterators to wchar_t. If the file contains other types of multibyte characters then chances are it'll need extra effort to do the right thing.

Quote:

---

Originally Posted by laserlight

You need to elaborate on what exactly is this delimiter removal about.


<algorithm> is the correct header.


In my example, I am applying transform to the elements of the string, and then assigning the result to those same elements.


jeffcobb's myStrLwr example is a function that takes a std::string argument by value and returns a std::string object. It has nothing to do with files. Personally, I would have taken the argument by non-const reference and modified it as demonstrated in my example. In such a case, the return type can be void.

---

I should have done it by reference but figured the heart of the method was what was of educational value (if any)...as for doing it as a file, I would have mmapped the file and iterated over the contents that way...simple and fast.

Quote:

---

// 'out' now contains a lowercased version of in

---

ok it compiles but how do you get it to write to the file ? i tried out << out and nothing in the file. have been using string s and doing out << s which works. so would something like

Code:

---

  string s;
  out << s(out) ;

---

work ?

nope got

Quote:

---

44 C:\Dev-Cpp\project333 misc\stringtolowercvc.cpp no match for call to `(std::string) (std::ofstream&)'

---