tolower error

Bonjour guys!

I'm not very familiar to the function tolower() and when i tried it, i get some kind of error.

Here's some of my code:

Code:

#include <iostream>
#include <cctype>


    string swedish[0];
    swedish[0] = "hej";
    swedish[1] = "vem";
    
    //Alla våra engelska ord i en array
    string english[0];
    english[0] = "hi";
    english[0] = "who";
    
    //Kör en while-sats för att alla ord ska vara med
    while (done < quantity) 
    {
          
          string lower = tolower(english[done]); //Gör alla bokstäver små
          
          if (insert = lower) //kollar om det är rätt
          {
          } 
    done++;
    }
}

#1. The declarations of the english and swedish arrays need to indicate at least 2 elements, i.e.

Code:

string swedish[2];
swedish[0] = "hej";
swedish[1] = "vem";
    
//Alla våra engelska ord i en array
string english[2];
english[0] = "hi";
english[1] = "who";

#2.

Code:

if (insert = lower) //kollar om det är rätt

I'm sure you meant:

Code:

if (insert == lower) //kollar om det är rätt

#3.

Code:

string lower = tolower(english[done]); //Gör alla bokstäver små

tolower returns an int, not a char or a string. It also accepts an int as an argument, not a string. This function works on a character-by-character basis meaning you would have to apply it in a loop of some sort. The int argument and return value is the representation of the lowered character value.

Don't write the lowercasing code in-line. Write it once as a function, then use it multiple times. This function converts strings to lowercase:

Code:

#include <string>
#include <iterator>
#include <cctype>

std::string string_lower(const std::string &str)
{
   std::string x;
   std::transform(str.begin(), str.end(), std::back_inserter(x), tolower);
   return x;
}

Gets an error about the transform()

Code:

Code:

#include <iostream>
#include <cctype>
#include <iterator>

using namespace std;

string string_lower(const string &str)
{
   string x;
   transform(str.begin(), str.end(), back_inserter(x), tolower);
   return x;
}

int main(int argc, char *argv[])
{
    //Alla v&#229;ra svenska ord i en array
    string swedish[2];
    swedish[0] = "hej";
    swedish[1] = "vem";
    
    //Alla v&#229;ra engelska ord i en array
    string english[2];
    english[0] = "hi";
    english[1] = "who";
    
    /*Alla ord ska ligga i ordning s&#229; att swedish[2] representerar det svenska ordet f&#246;r english[2]*/
    //Precis XD
    
    string insert; //Namnet p&#229; stringen som anv&#228;ndaren skriver in i
    int quantity = 3; //Hur m&#229;nga ord det finns + 1. Om det finns 2 fr&#229;gor ska det vara 3 h&#228;r. Om det &#228;r 4 fr&#229;gor ska det vara 5 h&#228;r.
    int done = 0; //Hur m&#229;nga ord som har blivit svarade
    int points = 0; //Hur m&#229;nga po&#228;ng man f&#229;r
    
    //Skriver ut en text
    cout << "H&#228;r kommer du f&#229; svenska ord som du ska &#246;vers&#228;tta!\nD&#229; b&#246;rjar vi!\n\n\n";
    
    //K&#246;r en while-sats f&#246;r att alla ord ska vara med
    while (done < quantity) 
    {
          cout << "Vad heter " << swedish[done] << " p&#229; engelska?\n"; //Skriver ut vad heter lala beronde p&#229; vilket ord det &#228;r
          cin >> insert; //L&#229;ter anv&#228;ndaren skriva in ett ord
          
          string lower = string_lower(swedish[done]); //G&#246;r alla bokst&#228;ver sm&#229;
          
          if (english[done] == lower) //kollar om det &#228;r r&#228;tt
          {
                     points = points + 1; //L&#228;gg till 1 po&#228;ng
          } 
    done++;
    }
    
    cout << "Du fick " << points << " po&#228;ng!";
}

That's because transform() is in <algorithm>.

Originally Posted by dwks

That's because transform() is in <algorithm>.

Whoopsie. I hate how standard headers include each other willy-nilly. On my system the #include <algorithm> isn't needed (I think <iterator> pulls it in) so I didn't catch that.

Nice save.

Same error:
11 C:\Users\Fredrik\Desktop\main.cpp no matching function for call to `transform(__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::back_insert_iterator<std::string>, <unknown type>)'

Why is that?

EDIT:

Got Dev-C++ if that mathers

Originally Posted by Livijn

Same error:
11 C:\Users\Fredrik\Desktop\main.cpp no matching function for call to `transform(__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::back_insert_iterator<std::string>, <unknown type>)'

Why is that?

The clue is that <unknown type> thing at the end. It apparently doesn't know what tolower is. This is problematic because on many systems, tolower() is defined as a macro instead of a function. On my system, the <cctype> header undefines these macros and replaces them with true functions. Apparently your system does not. So... Try wrapping it up like this:

Code:

class lower
{
public:
    char operator()(char ch) { return tolower(ch); }
};

And then replace the "tolower" in the transform call with "lower()" (note the parentheses) -- does that work?

It's because of tolower(), which should be std::tolower(). [edit] You can use tolower() if you include <ctype.h>, but <cctype> puts everything in the std namespace as far as I know. [/edit]

You don't have to use transform(). Here's another way to do it.

Code:

#include <string>
#include <iterator>
#include <cctype>

std::string string_lower(const std::string &str) {
    std::string x;
    for(std::string::iterator i = str.begin(); i != str.end(); ++ i) {
        x += std::tolower(*i);
    }

    return x;
}

Now i get another error

17 C:\Users\Fredrik\Desktop\main.cpp expected primary-expression before ')' token

Code:

#include <iostream>
#include <cctype>
#include <iterator>
#include <algorithm>

using namespace std;

string string_lower(const string &str)
{
       class lower
       {
             public:
                    char operator()(char ch) { return tolower(ch); }
       };

   string x;
   transform(str.begin(), str.end(), back_inserter(x), lower);
   return x;
}

Originally Posted by dwks

It's because of tolower(), which should be std::tolower().

You don't have to use transform(). Here's another way to do it.

That's just a hand-coded transform()... Why do that when you already have it? And yeah, std::tolower is probably the right way.

I caught you in mid-edit when you said you suspected back_inserter to be the problem... back_inserter DOES return an output iterator -- this is the whole purpose of it.

Originally Posted by Livijn

Now i get another error

I TOLD you not to forget the parentheses on lower()

But then i get the same error as earlier with tolower()

Originally Posted by Livijn

But then i get the same error as earlier with tolower()

Are you sure it's the same? Can you post it?

17 C:\Users\Fredrik\Desktop\main.cpp no matching function for call to `transform(__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::back_insert_iterator<std::string>, string_lower(const std::string&)::lower)'