References

• YooLex Functions and Macros
• YooLex Data Types
• Command Line Options
• Configurations
• Input Format Overview
• Section 1 Description
• Section 2 Description
• Section 3 Description

YooLex Functions and Macros

Note: all macros can be accessed only in the lex file.

1. Only works if "char" option is used.
2. Only works if "line" option is used.
3. Only works if "bol" option or BOL states are used.

Data Types

These are the data types defined in yoogroup::YooLex<YYS_TYPE, YYTEXT_TYPE>., which is the parent class of all scanner classes.

Command line option

Usage: yoolex [options] file
Options:
  -h, -u, -?	print this message
  -b		report any DFA backups
  -c class	specify the C++ class name
  -i		use indirect threading for the g++ compiler
  -m		generate a main function
  -t table	specify the DFA table option
	-tm	generate a maximumly compressed table
	-te	generate an equivalence class table
	-tf	generate a full table
  -w		do not generate warning messages

Example:

	yoolex -i -tf lex.l

Configurations

Configurations are started by %option at the beginning of a line in section 1 of the input file.

An example of using some of the configurations.

%option class = "test"

Overview

The YooLex input file is divided into three sections. The first section contains configurations and some C++ codes. The second section contains mostly regular expressions and the corresponding actions. The third section contains any C++ codes users wish to be included near the end of the generated source. In all sections, line comments (//) and block comments (/* ... */) are allowed. %% is used to seperate two sections.

// section 1

%%

%{
// section 2 prolog
%}

// section 2

%{
// section 2 epilog
%}

%%

// section 3

Section 1 Description:

The purpose of section 1 is to include codes necessary for the scanner as well as defining some regular expression (RegEx) pattern names. YooLex configurations are also specified here.

To insert code at the beginning of the C++ output file, use the following format:

%{
// code here will be echoed at the beginning of the generated
// C++ source file.
%}

Section 1 may contain useful name representation of some regular expressions:

PatternName	RegEx
IDENT		[A-Za-z]+
NUMBER		[0-9]+

Finally Section 1 may contain the declaration of inclusive and exclusive start conditions. The inclusive start condition is started with %s

%s CONDITION_1 CONDITION_2

The exclusive start condition is started with %x

%x CONDITION_1 CONDITION_2

The difference between two start conditions is that when no start conditions are specified, all RegEx actions are shared by inclusive conditions. For exclusive start conditions, the condition name must be explicitly specified for a given RegEx.

Section 2 Description:

Section 2 contains three parts, prolog, regular expression actions and epilog.

Prolog is located at the very beginning of the section 2 and it is started by %{ and ended by %}:

%{
// code here will be inserted at the beginning of class::yyLexCase () function.
// It is useful to has some code that does something whenever yycase () is
// called.  If indirect threading is used, all variables used must be declared in
// this section
%}

Then it comes the definition of various regular expressions and the actions triggered whenever those regular expressions are encountered. YooLex supports nested conditions like FLEX does. It also supports BOL (^), EOL ($), <<EOF>>, as well as trailing contexts in regular expressions. YooLex currrently can handle trailing contexts that contain either fixed headers like:

abc/d*e

or fixed trails like:

abc*/de

The following types of regular expressions are not supported:

abc*/c*e
abc*/d*e

Epilog is located at the very end of the section 2 and it is started by %{ and ended by %}:

%{
// code here will be inserted at the end of class::yyLexCase () function.
// It is useful to has some code that does some clean up works.  The code
// here is only reachable if the user code in the action does not contain
// return or yyterminate ().
%}

Section 3 Description:

All codes in this section are echoed as is at the bottom of the generated source code. So feel free to put class functions and main here.