RE: [ROOT] template constructor

From: Philippe Canal (pcanal@fnal.gov)
Date: Mon Mar 15 2004 - 17:08:21 MET

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Hi Troy,

This problem is now fixed in the CVS repository.

Cheers,
Philippe.

-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Troy D. Straszheim
Sent: Saturday, February 28, 2004 9:57 PM
To: roottalk@pcroot.cern.ch
Subject: [ROOT] template constructor



Hey rooters -

How about this: I would like to allow automatic type conversion via
constructor.

With these classes:

struct C { };

struct A {
  A() { };

  template <class U>
  A(const U& u) { cout << __PRETTY_FUNCTION__ << endl; }

  template <class U>
  void doit(const U& u) { cout << __PRETTY_FUNCTION__ << endl; }
};

And the following linkdef:

#pragma link C++ class A+;
#pragma link C++ class C+;
#pragma link C++ function A::A(const C&);
#pragma link C++ function A::doit(const C&);

My sesson reports the following:

root [0] C c;
root [1] A a;
root [2] a.doit(c);
void A::doit(const U&) [with U = C]
root [3] A a2(c);
Error: Can't call A::A(c) in current scope FILE:(tmpfile) LINE:1
Possible candidates are...
filename       line:size busy function type and name  (in A)
(compiled)        0:0    0 public: A A(void);
(compiled)        0:0    0 public: A A(const A&);

The template function doit() works, but the copy constructor does not.  Any
ideas?

Cheers,

Troy Straszheim

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