REX

Section: User Commands (1)
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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)
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

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Time: 00:38:13 GMT, March 30, 2022