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Sep 11th, 2007

Variable scope problem

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Hi
I have the following code ...

main()
{
....
...
if(var==true)
{
Graph g1=CreateGraph<Graph>(vertex,edge);
}
else
{
Graph1 g1=CreateGraph<Graph1>(vertex,edge);
}

numvertex(g1);
}

When i m calling numvertex() function it says undefined identifier g1 what can be the solution for this. Provided I cannot make define the object globally or at the start of main(). Is there anyway out for this. I also tried making this static but no luck . Means the object scope ends as the If block ends.Plz help...

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tonyaim83

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Sep 11th, 2007

Re: Variable scope problem

I not at all clear with the solution you have provided . Kindly give some sample code for my problem,

tonyaim83

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Sep 11th, 2007

Re: Variable scope problem

Without seeing all the other code it is difficult to see what you are doing... One quick fix would be to add the function calls within the if statements. If you posted more about these Graph and Graph1 classes we would be able to help you find a better solution...

Last edited by redbaron; Sep 11th, 2007 at 11:41 am.

redbaron

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Sep 11th, 2007

Re: Variable scope problem

>Provided I cannot make define the object globally or at the start of main().
You have to define a variable before it's used, and you have to define a variable within a visible scope. What you're doing is illegal because g1 is defined in a nested scope but used beyond that scope. It has to be like this:

C++ Syntax (Toggle Plain Text)
int main()
{
  // ...
  Graph g1;
 
  if ( var )
    g1 = CreateGraph<Graph> ( vertex, edge );
  else
    g1 = CreateGraph<Graph1> ( vertex, edge );
 
  numvertex ( g1 );
}
int main()
{
  // ...
  Graph g1;

  if ( var )
    g1 = CreateGraph<Graph> ( vertex, edge );
  else
    g1 = CreateGraph<Graph1> ( vertex, edge );

  numvertex ( g1 );
}

>Provided I cannot make define the object globally or at the start of main().
If the unnamed block trick doesn't count, you're SOL:

C++ Syntax (Toggle Plain Text)
int main()
{
  // ...
 
  {
    Graph g1;
 
    if ( var )
      g1 = CreateGraph<Graph> ( vertex, edge );
    else
      g1 = CreateGraph<Graph1> ( vertex, edge );
 
    numvertex ( g1 );
  }
}
int main()
{
  // ...

  {
    Graph g1;

    if ( var )
      g1 = CreateGraph<Graph> ( vertex, edge );
    else
      g1 = CreateGraph<Graph1> ( vertex, edge );

    numvertex ( g1 );
  }
}

However, I fail to understand why you have this restriction. Perhaps you can enlighten us as to what program requirements are stopping you from defining a variable in the correct scope?

Narue

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Sep 11th, 2007

Re: Variable scope problem

If you would look closely he has 2 different Graph classes apparently, Graph and Graph1

C++ Syntax (Toggle Plain Text)
if(var==true)
{
Graph g1=CreateGraph<Graph>(vertex,edge);
}
else
{
Graph1 g1=CreateGraph<Graph1>(vertex,edge);
}
if(var==true)
{
Graph g1=CreateGraph<Graph>(vertex,edge);
}
else
{
Graph1 g1=CreateGraph<Graph1>(vertex,edge);
}

I initially posted the response that you had, before noticing that

redbaron

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Sep 11th, 2007

Re: Variable scope problem

>If you would look closely he has 2 different Graph classes apparently, Graph and Graph1
*sigh* I hate it when poor naming practices cause me to make a mistake.

Narue

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