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From: gls@THINK.COM (Guy Steele)
Newsgroups: comp.lang.scheme
Subject: why is quasiquote necessary?
Message-ID: <9006011846.AA15382@verdi.think.com>
Date: 1 Jun 90 18:46:11 GMT
References: <DIGEST.184.900531.031023.24@MC.LCS.MIT.EDU>
Sender: daemon@athena.mit.edu (Mr Background)
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   From: "Andrew L. M. Shalit" <cambridge.apple.com!alms@bloom-beacon.mit.edu>
   To: scheme@mc.lcs.mit.edu

   It occurred to me today that Scheme doesn't really need a quasiquote
   special form.  Instead, quote could have just been extended to handle
   unquote and unquote-splicing.

   I can only think of two reasons for having both quote and quasiquote:

    1) historical accident, because of the way the quasiquote special
       form was derived from a reader macro.
    2) program readability.  Some would argue that a large quoted piece of
       program text with a little bitty comma in the middle might be prone
       to misinterpretation (by humans).

      -andrew

There are some effects that cannot be achieved using quasiquote
only.  Consider, for example, an idiom I find myself using
frequently:

		`',x

which means about the same as (list 'quote x).

		``,x

does not mean the same thing at all because the comma
is captured by the inner quasiquote.

--Guy