Re: I'm having trouble understanding overloaded operators

From:
firstlast1234567890@yahoo.co.uk
Newsgroups:
comp.lang.c++
Date:
Fri, 14 Mar 2008 08:46:51 -0700 (PDT)
Message-ID:
<a3c094d0-b7de-4e7c-9ca3-708acd2d5ac5@x30g2000hsd.googlegroups.com>
On Mar 14, 3:28 pm, Triple-DES <DenPlettf...@gmail.com> wrote:

On 14 Mar, 16:03, firstlast1234567...@yahoo.co.uk wrote:

Hello, I am trying to understand overloaded operators but am getting
confused as to how I can provide a conversion from my number class and
the scalar types?

If I create a class that represents a fictional number type, I
understand that I can create an overloaded assignment operator that
will accept long int for example. What I do not understand is how I
create an assignment operator to do the reverse, i.e. assign my
numeric class value to the scalar long int?

class myLong
{
        public:
                myLong()
                        : val(0)
                {
                };

                myLong(long val)
                        : val(val)
                {
                };

                myLong(const myLong& that)
                        : val(that.val)
                {
                };

                myLong& operator=(const myLong& that)
                {

                        if (this != &that)
                        {
                                this->val = const_cast<myLong&>(that).getVal();
                        }

                        return(*this);
                };

                long getVal()
                {
                        return(val);
                };

        private:
                long val;

};

So this works for something like

myLong mylong;
mylong = 42;
long scalarLong = mylong.getVal();
myLong newLong = mylong;
scalarLong++;
mylong = scalarLong;

But how do I do something like this

myLong myLongTest;
myLongTest = 1;
long scalarLong = myLongTest;

I do not know how to code this reverse assignment. I tried a few ways
but failed dismally.


Add the following member:

operator long() { return val; }

But keep in mind that there are pitfalls associated with such user-
defined conversion operators.

DP


That's silly, thank you so much, I just cannot see that in any
documentation. By "silly" I meant I really wanted to see a really
complex solution to justify my inability to work this out myself.
Could you recommend a good simple text that explains these sort of
things to someone who is just starting out? I have tried reading the
Kerningham reference that everyone alludes to but it is all Greek to
me.

Thank you.

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