Returning a vector of strings - c++

Question

I'm a bit confused with all the namespaces for vector and how to properly return a vector of strings in my class. Here is the code:
main.cpp
#include <fstream>
#include <iostream>
#include <stdlib.h>
#include <vector>
#include <string>
#include "lab1.h"
using namespace std;
readwords wordsinfile;
words wordslist;
int main ( int argc, char *argv[] )
{
if ( argc != 2 ) {
// Looks like we have no arguments and need do something about it
// Lets tell the user
cout << "Usage: " << argv[0] <<" <filename>\n";
exit(1);
} else {
// Yeah we have arguements so lets make sure the file exists and it is readable
ifstream ourfile(argv[1]);
if (!ourfile.is_open()) {
// Then we have a problem opening the file
// Lets tell the user and exit
cout << "Error: " << argv[0] << " could not open the file. Exiting\n";
exit (1);
}
// Do we have a ASCII file?
if (isasciifile(ourfile)) {
cout << "Error: " << argv[0] << " only can handle ASCII or non empty files. Exiting\n";
exit(1);
}
// Let ensure we are at the start of the file
ourfile.seekg (0, ios::beg);
// Now lets close it up
ourfile.close();
}
// Ok looks like we have past our tests
// Time to go to work on the file
ifstream ourfile2(argv[1]);
wordsinfile.getwords(ourfile2);
lab1.h
#ifndef LAB1_H
#define LAB1_H
bool isasciifile(std::istream& file);
class readwords {
public:
int countwords(std::istream& file);
std::vector<std::string> getwords(std::istream& file);
};
class words {
public:
void countall( void );
void print( void );
};
#endif
lab1.cpp
#include <fstream>
#include <iostream>
#include <map>
#include "lab1.h"
#include <vector>
using std::vector;
#include <string>
using namespace std;
vector<string> readwords::getwords(std::istream& file) {
char c;
string aword;
vector<string> sv;
int i = 0;
while(file.good()) {
c = file.get();
if (isalnum(c)) {
if(isupper(c)) {
c = (tolower(c));
}
if(isspace(c)) { continue; }
aword.insert(aword.end(),c);
} else {
if (aword != "") {sv.push_back(aword);}
aword = "";
i++;
continue;
}
}
return sv;
}
Here is the error from compiling.
g++ -g -o lab1 -Wall -pedantic main.cpp lab1.cpp
In file included from lab1.cpp:4:0:
lab1.h:9:4: error: ‘vector’ in namespace ‘std’ does not name a type
lab1.cpp:48:54: error: no ‘std::vector<std::basic_string<char> > readwords::getwords(std::istream&)’ member function declared in class ‘readwords’
make: *** [lab1] Error 1
Why do I get this error and how do I fix it. Thank you for any help you can provide.
Ryan

Answer 1

You have to #include <vector> in the header file as well. Actually, including it in the header is enough, as all files including that header will implicitly also include <vector>.
The thing is your include order is:
#include "lab1.h"
#include <vector>
and since you use std::vector in the header (before including it) you get the error. Reversing the include order would fix the compilation error, but doesn't solve the underlying error - that lab1 uses symbols that weren't defined yet. The proper fix is to include <vector>.

Answer 2

The compiler looks at code in the order it's written. That also applies to #include directives: the contents of the file are treated as if they had been written in the file that #include's them. As #LuchianGrigore has mentioned, the best solution is to add
#include <vector>
to "lab1.h". But you could hide the problem by moving the #include <vector> in "lab1.cpp" so that it comes before the #include "lab1.h". That would make the error go away, because the compiler would have already read` before it started to read "lab1.h". That's not what you should do, but it's the kind of thing that can happen accidentally and hide the actual problem.