pop@cs.umass.edu (02/14/91)
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.