Re: Perl style hash

From:
Stuart Redmann <DerTopper@web.de>
Newsgroups:
comp.lang.c++
Date:
Thu, 10 Sep 2009 01:15:35 -0700 (PDT)
Message-ID:
<8e4e8540-069e-4187-9a7b-39442d8796e7@r9g2000yqa.googlegroups.com>
On 10 Sep., 07:45, none <n...@none.none> wrote:

Sam wrote:

So? This calls for an overloaded Anything::operator=():

class Anything {

public:
   // ..

   Anything &operator=(double);
   Anything &operator=(int);
   Anything &operator=(std::string);
};

Okee-dokee.

And even if you could, you still wouldn't have the perl-style
behavior that I described. If you tried:

   x["root"]["branch"]["leaf"] = 5;

the compiler would not know how to resolve the second (and third) set
of braces.


Of course it would. It's merely a matter of implementing operator[]()
accordingly.


I like the simplicity of this approach. The way I'm doing it now, I'll
have to add an iterator class to my wrapper, etc, which stinks. Your w=

ay,

I'd just be using std::map directly.

But I still don't quite see how the second and third sets of [] would wor=

k.

The first one, x["root"], is going to return an Antyhing&. So, class
Anything would have to also have a [] operator. How would the returned
Anything object access "x", which would be of type std::map?- Zitierten T=

ext ausblenden -

Try this:

#include <map>
#include <string>
#include <iostream>

#include <boost\any.hpp>

class CHashMapNode
{
private:
  typedef std::map<std::string, CHashMapNode*> TNodeType;
  TNodeType m_Node;

  boost::any m_Value;

public:
  CHashMapNode& operator[] (const char* KeyName)
  {
    // Look up the key in our map. If it doesn't exist, create one.
    CHashMapNode*& NewNode = m_Node[std::string (KeyName)];
    if (!NewNode)
      NewNode = new CHashMapNode;
    return *NewNode;
  }

  CHashMapNode& operator= (const boost::any& p_NewValue)
  {
    m_Value = p_NewValue;
    return *this;
  }

  boost::any GetValue () const
  {
    return m_Value;
  }
};

int main(int argc, char* argv[])
{
  CHashMapNode HashMap;
  HashMap["Root"]["Subnode"] = 3;
  std::cout << boost::any_cast<int>
               (HashMap["Root"]["Subnode"].GetValue ());

  HashMap["Root"]["Subnode"] = std::string ("Hello World");
  std::cout << boost::any_cast<std::string>
               (HashMap["Root"]["Subnode"].GetValue ());
  return 0;
}

Regards,
Stuart

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