From: Arlen Christian Mart Cuss <celtic@...>
Date: 2007-10-23T22:39:13+09:00
Subject: Re: How does overload work in ruby?


On Mon, 2007-10-22 at 21:31 +0900, Rick DeNatale wrote:
> > If you want to allow the caller to select the default value
> > explicitly you may say
> >
> >   def sum a, b, c = nil
> >     c ||= 0
> >     a + b + c
> >   end
> 
> It seems to me that this is just a slightly less efficient way of
> doing the same thing as the code you quoted.
> 
> In either case the caller isn't specifying the default value, it's
> overriding the default.
> 
> In the call sum(1,2)  ruby will evaluate the default expression for c,
> in the call sum(1,2,3) it won't since c has a value given by the third
> parameter.  Making the default value of c nil, and then doing c ||= 0
> justs slows down both cases.

It also means that if the caller really wants to pass nil, it'll get
turned to the default value.

 - Arlen