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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.compilers
Subject: Re: A minimal LL(1) parser generator ?
Date: Sat, 25 Jan 2020 18:25:50 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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carlglassberg@gmail.com writes:
>Anton, I now see that, in Gray, the precedence of "&&" is higher than every other operator.

Among the postfix operators, precedence is determined by the way they
are written down.  But yes, if you see (( a b || c d )) as having two
infix operators, || and the empty operator, then you can write a
precedence hierarchy:

postfix
empty
||

>So Gray EBNF:
>a b && c d && e f && <- x

Correctly written as

(( a b && c d && e f && )) <- x

>is equivalent to Wirth EBNF:
>
>x = a { b a } c { d c } e { f e } .

Yes.

>Likewise:
>
>a b && ? <- x

a b && ?? <- x

>is
>x = [ a { b a } ] .

Yes.

- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/