🚀 go-pugleaf

>/* Written  8:12 am  Oct 22, 1988 by jkim@uhccux.uhcc.hawaii.edu */
>> <<<<<<<<<<<<***<<<<<<<<<<<<***<<<<<<***>>>>>>***>>>>>>>>>>>>***>>>>>>>>>>>>
>Clay Bond wrote:
>
>> a CFL is not going to describe English.
>
>Could you tell us a convincing evidence for this?
>If you are going to bring up 50's argument based on a long-distant 
>dependency, I would recommend you to read first Gerald Gazdar (1982) Phrase
>structure grammar. In Pauline Jacobson and Geoffrey K. Pullum (eds),
>The Nature of Syntactic Representation. Dordrecht: D. Reidel, 131-186.
>/* End of text */

Context-free languages have enough trouble adequately describing
programming languages.  Sure, they can do a half-decent job on the written
syntax as it appears in the file.  But to use syntactical productions to
recognize things such as various data types in expressions, or even worse,
checking that the number of parameters agrees between a caller and a callee
is either too exhaustive to be useful or just simply beyond a CFL.  Hey, if
a context-free grammer can't recognize the regular expression

              x  y  z  y  x     (note: this requires a pushdown machine with
	     a  b  c  b  a             multiple stacks, more power than an 
				       automata equivalent to a CFL can be)

how the hell is it going to handle English, or Spanish, or whatever?
Remember, we must check proper pluralization, subject-verb agreement, all
that good stuff.  For programming languages, the CFL describes the written
syntax and the semantic actions fill in the context-sensitive features
we need.  My wild guess is that our minds use a context-sensitive grammar
with hundreds of thousands of semantic checks to fill in where the CSG 
is inadequate for our needs.


Doug Scofield                          dougs@ssd.harris.com
Harris Computer Systems        {uunet,mit-eddie,novavax}!hcx1!dougs
Ft. Lauderdale, FL                     voice: (305) 973 5340