143 lines
4.2 KiB
Groff
143 lines
4.2 KiB
Groff
.\" $Id$
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.TH LLGEN 1 "$Revision$"
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.ad
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.SH NAME
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LLgen, an extended LL(1) parser generator
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.SH SYNOPSIS
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LLgen [ \-vxwans ] [ \-j[\fInum\fP] ] [ \-l\fInum\fP ] [ \-h\fInum\fP ] file ...
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.SH DESCRIPTION
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\fILLgen\fP
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converts a context-free grammar into a set of
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functions which form a recursive descent parser with no backtrack.
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The grammar may be ambiguous;
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ambiguities can be broken by user specifications.
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.PP
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\fILLgen\fP
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reads each
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\fIfile\fP
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in sequence.
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Together, these files must constitute a context-free grammar.
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For each file,
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\fILLgen\fP
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generates an output file, which must be compiled by the
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C-compiler.
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In addition, it generates the files
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\fILpars.c\fP
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and
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\fILpars.h.\fP
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\fILpars.h\fP
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contains the
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\fIdefine\fP
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statements that associate the
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\fILLgen\fP-assigned `token-codes' with user declared `token-names'.
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This allows other source files, for instance the source file
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containing the lexical analyzer,
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to access the token-codes by
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using the token-names.
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\fILpars.c\fP
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contains the error recovery routines and tables. It must also
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be compiled by the C-compiler. When the generated parser uses non-correcting
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error recovery (
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\fB\-n\fP
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option)
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\fILLgen\fP
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also generates a file
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\fILncor.c\fP
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that contains the non-correcting recovery mechanism.
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.PP
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\fILLgen\fP
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will only update those output files that differ from their previous
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version.
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This allows
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\fILLgen\fP
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to be used with
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\fImake\fP
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(1) convieniently.
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.PP
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To obtain a working program, the user must also supply a
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lexical analyzer, as well as
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\fImain\fP
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and
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\fILLmessage\fP,
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an error reporting routine;
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\fILex\fP
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(1) is a useful program for creating lexical analysers usable
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by
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\fILLgen\fP.
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.PP
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\fILLgen\fP accepts the following flags:
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.IP \fB\-v\fP
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create a file called
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\fILL.output\fP,
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which contains a description of the conflicts that
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were not resolved.
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If the flag is given more than once,
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\fILLgen\fP
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will be more "verbose".
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If it is given three times, a complete description of the
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grammar will be supplied.
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.IP \fB\-o\fP
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Specifies the location of the output files. If not set, they
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are placed in the current directory.
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.IP \fB\-x\fP
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the sets that are computed are extended with the nonterminal
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symbols and these extended sets are also included in the
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\fILL.output\fP
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file.
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.IP \fB\-w\fP
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no warnings are given.
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.IP \fB\-a\fP
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Produce ANSI C function headers and prototypes.
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.IP \fB\-n\fP
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Produce a parser with non-correcting error recovery.
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.IP \fB\-s\fP
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Simulate the calling of all defined subparsers in all semantic actions. When
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using non-correcting error recovery, subparsers that are called in semantic
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actions may cause problems; this flag provides a `brute-force' solution.
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.IP \fB\-j\fP[\fInum\fP]
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when this flag is given, \fILLgen\fP will generate dense switches,
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so that the compiler can generate a jump table for it. This will only be
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done for switches that have density between
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\fIlow_percentage\fP and \fIhigh_percentage\fP, as explained below.
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Usually, compilers generate a jumptable when the density of the switch
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is above a certain threshold. When jump tables are to be used more often,
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\fIhigh_percentage\fP must be set to this threshold, and \fIlow_percentage\fP
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must be set to a minimum threshold. There is a time-space trade-off here.
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.I num
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is the minimum number of cases in a switch for the \fB\-j\fP option to be
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effective. The default value (if
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.I num
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is not given) is 8.
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.IP \fB\-l\fP\fInum\fP
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The \fIlow_percentage\fP, as described above. Default value is 10.
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.IP \fB\-h\fP\fInum\fP
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The \fIhigh_percentage\fP, as described above. Default value is 30.
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.SH FILES
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LL.output verbose output file
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.br
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Lpars.c the error recovery routines
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.br
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Lncor.c non-correcting error recovery mechanism
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.br
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Lpars.h defines for token names
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.SH "SEE ALSO"
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\fIlex\fP(1)
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.br
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\fImake\fP(1)
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.br
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\fILLgen, an Extended LL(1) Parser Generator\fP
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by C.J.H. Jacobs.
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.br
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\fITop-down Non-Correcting Error Recovery in LLgen\fP
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by A.W van Deudekom and P.J. Kooiman
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.SH DIAGNOSTICS
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Are intended to be self-explanatory. They are reported
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on standard error. A more detailed report is found in the
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\fILL.output\fP
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file.
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.SH AUTHOR
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Ceriel J. H. Jacobs
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.br
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The non-correcting error recovery mechanism is written by
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A.W van Deudekom and P.J. Kooiman.
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