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From: pop@cs.umass.edu
Newsgroups: comp.lang.prolog
Subject: Shriek as an operator.
Message-ID: <26581@dime.cs.umass.edu>
Date: 13 Feb 91 19:18:24 GMT
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What is interesting is that Poplog Prolog has exactly the same behaviour,
namely that a postfix '!' gives a syntax error if '!' can be an infix.
The parser, by Simon Nichols and Rob Duncan is implemented POP-11, so 
one might expect it to be independent, tho' I don't know whether they made
use of the code of C-prolog in writing it.