🚀 go-pugleaf

richardcrane wrote:
> 
> can somebody help me iam a beginner in C++.  I want to pass an array between
> 3 different functions that are a user definable size.  what method is the
> best to start with as i dont have a clue.
> 
As a beginner, you should be using std::vector<> not arrays, especially if
you need to track a variable size.

richardcrane wrote:
> 
> can somebody help me iam a beginner in C++.  I want to pass an array between
> 3 different functions that are a user definable size.  what method is the
> best to start with as i dont have a clue.


std::vector is a resizable array class.

e.g.

typedef std::vector<std::string> strings;

strings tokenize(const char *line)
{
    strings res;
    ...
    res.push_back(str);
    ...
    return res;
}

strings r = tokenise("echo \"foo bar\" wiz");
assert(r.size() == 3);
assert(r[0] == "echo");
assert(r[1] == "foo bar");
assert(r[2] == "wiz");

HTH
alan

-- 
Alan Donovan, ARM Research, ARM Ltd.        alan.donovan@arm.com

just pass pointer to the first element of the array. for an array of char

f(char *array1ptr);

:)
richardcrane <richardcrane@ntlworld.com> wrote in article
<Ahxi6.6779$mO6.136359@news6-win.server.ntlworld.com>...
> can somebody help me iam a beginner in C++.  I want to pass an array
between
> 3 different functions that are a user definable size.  what method is the
> best to start with as i dont have a clue.
> 
> cheers
> Rick
> 
> 
> 

richardcrane wrote:
> 
> can somebody help me iam a beginner in C++.  I want to pass an array between
> 3 different functions that are a user definable size.  what method is the
> best to start with as i dont have a clue.
> 

The C way:
**********

#include <stdio.h>

void Foo1( int* Array, int ArraySize )
{
  for( int i = 0; i < ArraySize; ++i )
    printf( "%d\n", Array[i] );
}

void Foo( int* Array, int ArraySize )
{
  Foo1( Array, ArraySize );
}

int main()
{
  const int Size = 10;
  int Test[Size];

  for( int i = 0; i < Size; ++i )
    Test[i] = 100 + i;

  Foo( Test, Size );

  return 0;
}

the C++ way:
************

#include <iostream>
#include <vector>

using namespace std;

typedef vector< int > IntArray;

void Foo1( IntArray& Array )
{
  for( int i = 0; i < Array.size(); ++i )
    cout << Array[i] << '\n';
}

void Foo( IntArray& Array )
{
  Foo1( Array );
}

int main()
{
  IntArray Test( 10 );

  for( int i = 0; i < Test.size(); ++i )
    Test[i] = 100 + i;

  Foo( Test );

  return 0;
}

-- 
Karl Heinz Buchegger
kbuchegg@gascad.at

In article <Ahxi6.6779$mO6.136359@news6-win.server.ntlworld.com>,
richardcrane <richardcrane@ntlworld.com> wrote:
>can somebody help me iam a beginner in C++.  I want to pass an array between
>3 different functions that are a user definable size.

I take it you mean the array size is defined by the user when the program 
runs?  Maybe this will give you the idea:

  #include <iostream>

  using namespace std; // quick and dirty namespace hack

  void ReadData (double d[], int size)
  {
      for (int k = 0; k < size; ++k)
      {
          cout << "Enter d[" << k << "]: ";
          cin >> d[k];
      }
  }

  void DisplayData (double d[], int size)
  {
      for (int k = 0; k < size; ++k)
      {
          cout << "d[" << k << "] = " << d[k] << endl;
      }
  }

  int main ()
  {
    cout << "How many data items? ";
    int howmany;
    cin >> howmany;
    double *data = new double[howmany]; // allocate the array dynamically
    ReadData (data, howmany);  // must pass the size, too
    DisplayData (data, howmany);
    delete [] data;  // clean up after yourself when done
    return 0;
  }


This is easier using vectors instead of arrays:


  #include <iostream>
  #include <vector>

  using namespace std; // quick and dirty namespace hack

  void ReadData (vector<double>& d)
  {
      cout << "Enter data items one by one, hit ^D when finished...\n";
      double x;
      while (cin >> x)
      {
          d.push_back(x);  // vector automatically expands as needed
             // and keeps track of how much data it contains
      }
  }

  void DisplayData (vector<double>& d)
  {
      for (int k = 0; k < d.size(); ++k)
      {
          cout << "d[" << k << "] = " << d[k] << endl;
      }
  }

  int main ()
  {
    // no need to ask for how much data
    // declare vector as zero-length initially
    vector<double> data;
    ReadData (data);  // vector keeps track of its own size
    DisplayData (data);
    // vectors clean up after themselves for you
    return 0;
  }

-- 
Jon Bell <jtbell@presby.edu>                        Presbyterian College
Dept. of Physics and Computer Science        Clinton, South Carolina USA

Karl Heinz Buchegger wrote:
>
> 
> the C++ way:
> ************
> 
> #include <iostream>
> #include <vector>
> 
> using namespace std;
> 
> typedef vector< int > IntArray;
> 
> void Foo1( IntArray& Array )
> {
>   for( int i = 0; i < Array.size(); ++i )
>     cout << Array[i] << '\n';
> }

or
   for(vector<int>::iterator it = Array.begin(); it != Array.end(); ++it)
	cout << *it << '\n';

Arrays are always passed by reference not by value.  Even when you don't use
an ampersand it is still passed by reference.  I don't even think you can
add an ampersand.

--

Micah

{Eternity is not everlasting...}
"richardcrane" <richardcrane@ntlworld.com> wrote in message
news:Ahxi6.6779$mO6.136359@news6-win.server.ntlworld.com...
> can somebody help me iam a beginner in C++.  I want to pass an array
between
> 3 different functions that are a user definable size.  what method is the
> best to start with as i dont have a clue.
>
> cheers
> Rick
>
>

"Siper" <nospam@yahoo.com> wrote in message
news:sYzi6.95441$R5.4103496@news1.frmt1.sfba.home.com...
> Arrays are always passed by reference not by value.  Even when you don't
use
> an ampersand it is still passed by reference.  I don't even think you can
> add an ampersand.

Micah,

You can use the ampersand on an array (dereference it), but the method you
pass it to will probably complain.  It will probably say something about
passing an ArrayType** to a function that take an ArrayType*.

Bret

>
> --
>
> Micah
>
> {Eternity is not everlasting...}
> "richardcrane" <richardcrane@ntlworld.com> wrote in message
> news:Ahxi6.6779$mO6.136359@news6-win.server.ntlworld.com...
> > can somebody help me iam a beginner in C++.  I want to pass an array
> between
> > 3 different functions that are a user definable size.  what method is
the
> > best to start with as i dont have a clue.
> >
> > cheers
> > Rick
> >
> >
>
>

He said hes a begginer, pointers are not for the newbie!

Phil Jackson