alms@cambridge.apple.com (Andrew L. M. Shalit) (05/31/90)
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).
-andrewkend@tekchips.LABS.TEK.COM (Ken Dickey) (05/31/90)
In article <ALMS.90May30153205@brazil.cambridge.apple.com> alms@cambridge.apple.com (Andrew L. M. Shalit) writes: > >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. Quoted data is constant [e.g. EPROMable]. My recollection is that quasi-quoted forms may expand into something not quite constant. I can't immediately think of a good example [nested quasi-quotes?] {JAR, are you out there?}. -Ken Dickey kend@mrloog.WR.TEK.COM
dak@sq.sq.com (David A Keldsen) (06/01/90)
alms@cambridge.apple.com (Andrew L. M. Shalit) writes: >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). I respectfully disagree [that Scheme doesn't need the quote-quasiquote distinction]. This (IMHO) is one of those places where full generality is *not* a good thing. In particular, both human and machine readers of quasiquoted phrases must scan the *entire* phrase, looking for unquotes...which is an efficiency loss. Quote allows one to say, "OK, stop looking, the rest is unevaluated." It's a common enough case that it is worth the difference in notation. > -andrew -- // David A. 'Dak' Keldsen: dak@sq.com or utai[.toronto.edu]!sq!dak // "I have heard the mermaids singing, each to each." -- T.S.Eliot
mac@k9.cad.mcc.com (Mac Michaels) (06/01/90)
alms@cambridge.apple.com (Andrew L. M. Shalit) writes: >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: I always thought that quasiquote was there to allow Scheme code to generate expressions that contain unquote and unquote-splicing symbols [, and ,@]. Quote does not process these symbols and thus allowing the generation of forms containing them. -- USPS: Mac Michaels, 3500 West Balcones Center Dr., Austin,TX 78759 ARPA: mac@mcc.com TELE: (512) 338-3509 FAX: (512) 338-3600 UUCP: {uunet,harvard,gatech,pyramid}!cs.utexas.edu!milano!cadillac!mac :-)))))))) She had so many chins, she looked like a piece of Lisp code!
gls@THINK.COM (Guy Steele) (06/02/90)
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.
--Guyalan@AI.MIT.EDU (Alan Bawden) (06/02/90)
Unfortunately `',x and '`,x don't mean the same thing.