String parameter errors

I'm trying to make a program that checks if a file is there, if not make it with some writting in it. I've done my best make sure everything is correct.

Code:

Code:

---

/* Section: header */
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>

/* Section: constant */
const std::string NEWLINE = "\n"
const std::string NEWLINE_FLUSH = "std::endl"

/* Section: prototype */
void nfound( const std::string &v_file );

int main( int argc, char *argv[] ) {
  using namespace std;
  string the_file = "test_file.txt";
  if ( "the_file" ) {
    cout << "File found!";
  } else {
    cout << "File not found!";
    nfound( "the_file" );
  }

  cin.get();
  return 0;
}

void nfound( const std::string &v_file ) {
  using namespace std;
  ofstream a_file ( "v_file" );
  a_file << "This text will go inside!NEWLINE";
  a_file.close();
}

---

Errors:

Quote:

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|9|error: expected ',' or ';' before 'const'|
||In function 'int main(int, char**)':|
|21|error: 'nfound' was not declared in this scope|

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You need semi-colons after the definitions of NEWLINE and NEWLINE_FLUSH.

I suspect, once you fix that, your code will not behave as you expect, as std::string's do not participate in concatenation of string literals. But you can experience that problem for yourself.

The darn semi-colons! Thanks for pointing that out! Can you explain your comment here:

Quote:

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Originally Posted by grumpy

I suspect, once you fix that, your code will not behave as you expect, as std::string's do not participate in concatenation of string literals. But you can experience that problem for yourself.

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I've just began programming and the furthest explaination of strings was C-style vs std::string.

The code

Code:

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  a_file << "This text will go inside!NEWLINE";

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will put the text "NEWLINE" into your output file, whereas I suspect you expect there to be an actual newline.

Wouldn't this code here replace anywhere that I put NEWLINE with \n? Kinda like an alias, that is the intended affect anyway...

Code:

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const std::string NEWLINE = "\n"

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That is my point. Look at the output file. You will find it does not.

Aliasing of variable names does not work inside string literals.

Think about it: would you really want the output of "some_stream << "Hello Peter"; to change if you subsequently modified the code to introduce a variable or macro in your code named Peter?

Oh I see now! So something to the tune of:

Code:

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a_file << "This text will go inside!" << NEWLINE;

---

What benefit that gives you over

Code:

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a_file << "This text will go inside!" << "\n";

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is questionable.

Note that it will not work with your definition of NEWLINE_FLUSH, as std::endl is not a character string.

The benefit is psychological, it might change later on when I advance through the tutorials and start actually programming. As for NEWLINE_FLUSH, I don't know how to make that one an alias, but I did it to highlight to myself that there is an alternative version to doing a newline.