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Re: [XP] Re: Polymorphism

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  • Ron Jeffries
    ... It seems to me that this whole discussion is oddly over-theoretical. An object might respond usefully to many different messages: draw: on some medium
    Message 1 of 100 , Aug 1, 2002
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      Around Thursday, August 1, 2002, 7:05:50 AM, Ilja Preuß wrote:

      >> Ilja said, in a discussion of GOF patterns, that a decorator typically
      >> isn't a subtype of the type it's decorating.
      >>
      >> GOF said that it is.
      >>
      >> The point was that Ilja was mistaken.

      > As I understand it, interface conformance is not sufficient for subtyping as defined by the LSP.

      It seems to me that this whole discussion is oddly over-theoretical.

      An object might respond usefully to many different messages:

      draw: on some medium
      send: as email
      encrypt: return a string of bytes
      save: to a file
      serialize: as an object

      There is little value, in my opinion, to thinking of this one object
      as being of a half-dozen different types or base classes. What matters
      is what it does ... what it knows how to do.

      The message is the message.

      Ron Jeffries
      www.XProgramming.com
      I have tried in my way to be free. -- Leonard Cohen
    • Kay A. Pentecost
      Hi, Jeff, Dossy, John, Brad, Everybody!! ... And a one and a two and... uh... wrong rhythm... ... Gee, Jeff, did you go to MIT??? Thanks to all for *all* the
      Message 100 of 100 , Aug 3, 2002
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        Hi, Jeff, Dossy, John, Brad, Everybody!!

        > -----Original Message-----
        > From: jeffgrigg63132 [mailto:jgrigg@...]
        > Sent: Saturday, August 03, 2002 1:50 PM
        > To: extremeprogramming@yahoogroups.com
        > Subject: Re: [XP] Lambada Calculus -vs- lambda-calculus
        >
        >
        > Lambada-Calculus
        > (A pun on "lambda-calculus") Teaching logic thru spanish dance steps.
        > Invented by P. van der Linden .
        > (1996-08-10)
        > -- foldoc

        And a one and a two and... uh... wrong rhythm...


        >
        >
        > Now as for "lambda-calculus"...
        > See: http://onlinedictionary.datasegment.com/word/lambda-calculus
        >
        > "A branch of mathematical logic developed by Alonzo Church in the
        > late 1930s and early 1940s, dealing with the application of functions
        > to their arguments." ... "Most functional programming languages are
        > equivalent to lambda-calculus [with some convenient extensions]."
        > (It's used in the LISP language, for instance.)
        >
        >
        > As a practical matter, it's a syntax for defining functions --
        > often "at run time."
        >
        > It's assumed that functions have no "side effects." That is, that
        > they perform some operation on their input arguments and return a
        > complex result -- but do not change global variables or data on disk
        > as a "side effect."
        >
        > To do this in Visual Basic, your functions would have to return
        > Collections and arrays, and many elements of those would be
        > Collections and arrays and other complext types, down to some
        > arbitrary level of nesting. This could be really confusing in Visual
        > Basic, but it can be an effective approach to handle complex
        > processing problems if done consistently, with appropriate language
        > support.
        >
        > Historically, these concepts have been used in artificial
        > intelligence and other highly data-driven applications.

        Gee, Jeff, did you go to MIT???

        Thanks to all for *all* the answers... sorry it took me so long to respond!!

        I didn't know unemployment would be so *hectic*!!

        First installment of Kay's Excellent Adventure at the XP Workshop starts
        next week!!

        Stay tuned!

        Kay




        >
        >
        >
        > --- Dossy <dossy@p...> wrote:
        > > Lambada calculus is a derivative of the sensual dance made popular
        > > in Brazil but employs a deep understanding of mathematics as part
        > > of the sensual ritual.
        > > -- Dossy
        >
        > > On 2002.08.02, jbrewer999 <jbrewer@j...> wrote:
        > > > "Kay A. Pentecost" <tranzpupy@i...> wrote:
        > > > > Now, what's lambda calculus...<ducking>
        >
        >
        >
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