Preset text for cin

[sam021384]

How can you preset suggested text for a cin?

E.g.

cout<<"Old value is: "<<oldVal<<" New value: ";
cin.SetPrefixText(oldVal);
cin>>newVal;

So the user sees:

Old value is: Sam New value: Sam


So, in this made-up scenario the user can just hit the Enter key to keep the existing value.

Is this even possible?

[Lindley]

Not possible using standard libraries only. If you go for platform-specific libraries, there is probably a way.

[JVene]

No, but you could wrap the concept into a function template

This is untested pseudo code, just to illustrate

template<T> GetValueWithDefault( T &o, T &n )
{
  T newVal;

  cout<<"Old value is: "<< o <<" New value: ";

  cin >> newVal;

  if ( IsNull( newVal ) ) 
      {
        newVal = o;
        cout << o;
      }
}

This code assumes you have an overload for a function IsNull which can evaluate any type T for "no entry" from cin.

The idea is simply to provide a function that takes the input, checks to see if nothing was entered, and output the default provided. Many variations on the theme are possible.