From: Its Me <itsme213@...>
Date: 2004-06-09T08:28:37+09:00
Subject: Re: Interfaces and semantics (or, how to hashpipe a duck)


"Hal Fulton" <hal9000@hypermetrics.com> wrote in message
> For example, imagine that we are concerned with a conceptual "append"
> operation. We want to know whether an object is capable of being
> appended onto.
>
> Well, a string is "appendable." So is an array. So is a file.
>
>    str  << x
>    arr  << x
>    file << x
>
> Aha! Why not just check for << existing?
>
> Oops. There's a Fixnum#<< which does a left shift!

The harder way is to specify the intended/guaranteed effect of the operation
(without committing to the implementation e.g. post-condition style
contracts).

A much easier improvement is to use meaningful parameter names and treat
them as part of the method selector.

    String#<<:item
    Array#<<:item
    File#<<:item
vs.
    Fixnum#<<:amount

Smalltalk does this. Imho, Ruby should do this when proper keyword arguments
are supported.