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Re: Who said that?

> From: "Anton van Straaten" <anton@appsolutions.com>
> Date: Fri, 18 Jul 2003 11:40:48 -0400
> > > there's a quote whose source and exact wording I can't recall.
> > > The sentiment goes something like: "When you read about it,
> > > [blank]; when you can teach it, [another blank]; when you
> > > can program it, you understand."  Does anyone know what this
> > > quote is?
> >
> > If we're thinking of the same quote, then Alan Perlis said that,
> > and it goes like:
> >
> > "You think you know when you learn, are more sure when you can
> > write, even more when you can teach, but certain when you can
> > program."
> In direct contrast to the claims in these quotes, I noticed this quote at
> the end of Part I of Pierce's "Types and Programming Languages":
> "Just because you've implemented something doesn't mean you understand it"
>    -- Brian Cantwell Smith
>   (...who, btw, has some interesting papers at
>   http://www.ageofsig.org/people/bcsmith/papers/ )
> Anton

If you've implemented it you still may not understand it.  But if you
*haven't* implemented it there's almost no chance that you understand it.
So implementation is necessary, but not always sufficient.

It reminds me of a joke/story I heard about two research groups, one
American and one French.  The American group had solved a practical
problem.  The French group looked at their solution and said "very nice,
but will it work in theory?"