freebsd-nq/share/doc/psd/15.yacc/ssb
Greg Lehey 38e505c3e5 Remove original license disclaimer.
Add Caldera license.

Approved by:    David Taylor <davidt@caldera.com>

Make roughly buildable under FreeBSD.

The results are not perfect: the original Makefile referred to a refer
file papers/Ind, which doesn't seem to have been kept, so the
references to other publications are missing.  In addition, the
pagination is not correct, with the result that some .DS/.DE blocks
leave large amounts of white space empty before them.  Possibly this
could be fixed by putting the (blank) footnotes at the end.

PR:   35345
Requested by:	Tony Finch <fanf@dotat.at>
2002-05-19 05:14:02 +00:00

148 lines
4.4 KiB
Plaintext

.\" Copyright (C) Caldera International Inc. 2001-2002. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions are
.\" met:
.\"
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.\" disclaimer.
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.\" Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\"
.\" This product includes software developed or owned by Caldera
.\" International, Inc. Neither the name of Caldera International, Inc.
.\" nor the names of other contributors may be used to endorse or promote
.\" products derived from this software without specific prior written
.\" permission.
.\"
.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" DISCLAIMED. IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
.\" OR OTHERWISE) RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
.\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" @(#)ssb 8.1 (Berkeley) 6/8/93
.\"
.\" $FreeBSD$
.SH
Appendix B: Yacc Input Syntax
.PP
This Appendix has a description of the Yacc input syntax, as a Yacc specification.
Context dependencies, etc., are not considered.
Ironically, the Yacc input specification language
is most naturally specified as an LR(2) grammar; the sticky
part comes when an identifier is seen in a rule, immediately
following an action.
If this identifier is followed by a colon, it is the start of the
next rule; otherwise
it is a continuation of the current rule, which just happens to have
an action embedded in it.
As implemented, the lexical analyzer looks
ahead after seeing an identifier, and
decide whether the next token (skipping blanks, newlines, comments, etc.)
is a colon.
If so, it returns the token C_IDENTIFIER.
Otherwise, it returns IDENTIFIER.
Literals (quoted strings) are also returned as IDENTIFIERS,
but never as part of C_IDENTIFIERs.
.sp
.nf
.ta .6i 1.2i 1.8i 2.4i 3i 3.6i
/* grammar for the input to Yacc */
/* basic entities */
%token IDENTIFIER /* includes identifiers and literals */
%token C_IDENTIFIER /* identifier (but not literal) followed by colon */
%token NUMBER /* [0-9]+ */
/* reserved words: %type => TYPE, %left => LEFT, etc. */
%token LEFT RIGHT NONASSOC TOKEN PREC TYPE START UNION
%token MARK /* the %% mark */
%token LCURL /* the %{ mark */
%token RCURL /* the %} mark */
/* ascii character literals stand for themselves */
%start spec
%%
spec : defs MARK rules tail
;
tail : MARK { \fIIn this action, eat up the rest of the file\fR }
| /* empty: the second MARK is optional */
;
defs : /* empty */
| defs def
;
def : START IDENTIFIER
| UNION { \fICopy union definition to output\fR }
| LCURL { \fICopy C code to output file\fR } RCURL
| ndefs rword tag nlist
;
rword : TOKEN
| LEFT
| RIGHT
| NONASSOC
| TYPE
;
tag : /* empty: union tag is optional */
| \'<\' IDENTIFIER \'>\'
;
nlist : nmno
| nlist nmno
| nlist \',\' nmno
;
nmno : IDENTIFIER /* NOTE: literal illegal with %type */
| IDENTIFIER NUMBER /* NOTE: illegal with %type */
;
/* rules section */
rules : C_IDENTIFIER rbody prec
| rules rule
;
rule : C_IDENTIFIER rbody prec
| '|' rbody prec
;
rbody : /* empty */
| rbody IDENTIFIER
| rbody act
;
act : \'{\' { \fICopy action, translate $$, etc.\fR } \'}\'
;
prec : /* empty */
| PREC IDENTIFIER
| PREC IDENTIFIER act
| prec \';\'
;
.fi
.bp