From: "Gregg N" 

Geo wrote:
> "Gregg N"  wrote in message
> news:419c0ffb{at}w3.nls.net...
>
>>     Operands(T a, T b) : a_(a), b_(b) { }
>
> what's the a_(a) stuff about?
>
> Geo.

A common convention is to stick an underscore at the beginning or end of
the name of a class member variable. In this case, a_ and b_ are the names
of the two variables that will store the operands. Another convention
commonly used Windows-based code is to use an m_ prefix.

The sequence

: a_(a), b_(b)

is an example of a constructor initializer list. It tells the compiler how
to provide arguments for the construction of the object's own member
objects. In this case the member objects are just built-in types, so I
could have done this as

Operands(T a, T b)
{
   a_ = a;
   b_ = b;
}

but that won't work for member objects whose constructors require
arguments, and is conceptually wrong because it theoretically means you are
constructing a_ and b_ and then assigning to them. For non-trivial objects
this would be inefficient.

Gregg

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