REX(1) GMD-Forschungsstelle-Karlsruhe REX(1)
NAME
rex - generator of lexical analysers
SYNOPSIS
rex [ -options ] [ -ldir ] [ file ]
DESCRIPTION
Rex generates programs to be used in lexical analysis of text. A
typical application is the generation of scanners for compilers. The
input file contains regular expressions to be searched for, and
actions written in C or Modula-2 to be executed when strings according
to the expressions are found. Unrecognized portions of the input are
copied to standard output. To be able to recognize tokens depending
on their context, Rex provides start states to handle left context and
the right context can be specified by an additional regular
expression. If several regular expressions match the input
characters, the longest match is preferred. If there are still several
possibilities, the regular expression given first in the specification
is chosen.
Rex generated scanners automatically provide the line and column
position of each token. For languages like Pascal and Ada where the
case of letters is insignificant tokens can be normalized to lower or
upper case. There are predefined rules to skip white space like
blanks, tabs, or newlines and there is a mechanism to handle include
files. The generated scanners are table-driven deterministic finite
automatons.
OPTIONS
a generate all (= sdm)
m generate a lexical analyser in Modula-2 (default)
c generate a lexical analyser in C
d generate a definition module for the lexical analyser
s generate support modules:
- a source module for input
- a main program to be used as test driver
r reduce the number of generated case/switch labels. Might be
necessary due to compiler restrictions. Effects: slower scanner
(2-4%), larger tables, same scanner size.
i use ISO 8 bit code (default: ASCII 7 bit code)
o optimize table size
Effects: slower scanner (0-15%), small tables, long generation
time (factor 1-10)
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REX(1) GMD-Forschungsstelle-Karlsruhe REX(1)
n do not optimize table size
Effects: fast scanner, large tables (factor 1-10), short
generation time
default: improve table size
Effects: slower scanner (0-5%), medium size tables (factor 1-2),
medium generation time (factor 1-2)
w suppress warnings
g generate # line directives
b do not partition charcater set into blocks
1 print statistics about the generated lexical analyser
ldir dir is the directory where Rex finds its table and data files
FILES
if output is in C:
<Scanner>.h specification of the generated scanner
<Scanner>.c body of the generated scanner
<Scanner>Source.h specification of support module source
<Scanner>Source.c body of support module source
<Scanner>Drv.c main program to serve as test driver
if output is in Modula-2:
<Scanner>.md definition module of the generated scanner
<Scanner>.mi implementation module of the generated scanner
<Scanner>Source.md definition module of support module source
<Scanner>Source.mi implementation module of support module source
<Scanner>Drv.mi main program to serve as test driver
<Scanner>.Tab tables to control the generated scanner
SEE ALSO
J. Grosch: "Rex - A Scanner Generator", GMD Forschungsstelle an der
Universitaet Karlsruhe, Compiler Generation Report No. 5, 1987
J. Grosch: "Efficient Generation of Lexical Analysers", Software -
Practice & Experience, 19 (11), 1089-1103, Nov. 1989
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