/share/doc/psd/15.yacc/ssd

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38.\" $FreeBSD$
39.SH
40Appendix D: Old Features Supported but not Encouraged
41.PP
42This Appendix mentions synonyms and features which are supported for historical
43continuity, but, for various reasons, are not encouraged.
44.IP 1.
45Literals may also be delimited by double quotes ``"''.
46.IP 2.
47Literals may be more than one character long.
48If all the characters are alphabetic, numeric, or \_, the type number of the literal is defined,
49just as if the literal did not have the quotes around it.
50Otherwise, it is difficult to find the value for such literals.
51.IP
52The use of multi-character literals is likely to mislead those unfamiliar with
53Yacc, since it suggests that Yacc is doing a job which must be actually done by the lexical analyzer.
54.IP 3.
55Most places where % is legal, backslash ``\e'' may be used.
56In particular, \e\e is the same as %%, \eleft the same as %left, etc.
57.IP 4.
58There are a number of other synonyms:
59.DS
60%< is the same as %left
61%> is the same as %right
62%binary and %2 are the same as %nonassoc
63%0 and %term are the same as %token
64%= is the same as %prec
65.DE
66.IP 5.
67Actions may also have the form
68.DS
69={ . . . }
70.DE
71and the curly braces can be dropped if the action is a
72single C statement.
73.IP 6.
74C code between %{ and %} used to be permitted at the
75head of the rules section, as well as in the
76declaration section.