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From: 70262.630@compuserve.COM (Iain Ferguson)
Newsgroups: comp.lang.scheme
Subject: EdScheme.
Message-ID: <"910606214037.70262.630.CHC124-1"@CompuServe.COM>
Date: 6 Jun 91 21:40:38 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
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Recent discussion of EdScheme does indeed concern a single product, which is 
written and marketed by Schemers Inc of Fort Lauderdale, FL, USA
(EMail: 71020.1774@compuserve.com), and is distributed in Europe by Lambda 
Publications of Swindon, Wiltshire, UK (EMail: 100015.1465@compuserve.com).
As Brian Harvey <bh@anarres.berkeley.edu> notes in his posting on the subject, 
Schemers Inc also offers an introductory CS text (The Schemer's Guide -- TSG) 
aimed at the high school, junior college, university freshman market that uses 
Scheme as its vehicular language.

Here are some comments upon Harvey's remarks:

1.  Both EdScheme and TSG distinguish unevaluated (Scheme) expressions from
    evaluated (data) expressions: Scheme expressions are black and data       
    expressions are red.  Harvey rightly observes that this color-coding 
    is a boon when explaining the evaluation of quote expressions and
    numbers. But, far from disguising Scheme's ability to treat procedures
    as first class objects, color-coding provides the teacher with a
    superlative tool for explaining how it is that Scheme procedures can
    input and output other Scheme procedures.

    In particular, it enables the teacher to clarify the crucial point that
    while the (black) expression '(lambda (x) x)' is NOT a procedure, the 
    (red) result of evaluating it IS.  I wonder how many beginning students 
    fully understand this point?  Armed with a clear and deep understanding,
    my ninth grade students (aged 15) manipulate higher order functions
    with ease.

    Incidentally, I gave my ninth grade class Part B, Section II of the
    1991 College Board Advanced Placement Computer Science exam to do
    without any warning or preparation of any kind, asking them to write
    their answers in Scheme.  (Regretfully, to have earned any credit for
    their efforts they would have had to have worked in Pascal.)  They all 
    found the test easy, in some cases trivial, and most had completed 
    their work in 15 minutes less than the 45 minutes normally allowed.
    And these students have had less than 40 hours of CS instruction,
    whereas the typical AP student is at least 2 years older and has sat
    through 360+ hours.

2.  Harvey alleges that in some instances EdScheme is incompatible with
    Abelson & Sussman's terminology.  A primary goal of TSG -- which is 
    supported by the manner in which EdScheme operates -- is to lay a solid
    foundation of *concepts* that are important in CS in general.  Once the
    concepts are firmly implemented, terminology becomes a trivial surface
    issue.  Students weaned on TSG and EdScheme pick up Abelson & Sussman
    and Springer & Friedman and rapidly adjust to the language and
    conventions used because they have a clear understanding of the
    basic concepts that are under discussion.

3.  One of EdScheme's virtues is its runnability from a floppy on 
    computers that have only modest amounts of memory available.  This
    brings Scheme to a much wider audience than if a hard drive were
    to be required (or even strongly recommended).  It is therefore
    unlikely ever to have the elbow room to be a Scheme implementation
    that is complete in every respect.  Great pains have been taken,
    however, to ensure that it is 100% upwardly compatible.  Learners
    who start out on EdScheme will be able to graduate on to
    implementations that have all the bells and whistles that Harvey
    mentions without having to unlearn anything.  Yet EdScheme is
    powerful enough to be able to accompany them during the period
    of transition to any other Scheme implementation.

Iain Ferguson.