.TH GEN-SCANNER 1 "24 January 1991" "Demeter" "Demeter Software"
.SH NAME
gen-scanner \- scanner generator for Demeter System/C++

.SH SYNOPSIS
.I gen-scanner

.SH DESCRIPTION 
.I gen-scanner 
is usually implicitely called by 
.I make
and generates the file lex.yy.c which is used by the Demeter generic
parser. Lex.yy.c depends on the lex file lex-DEM.l which in turn
consists of the following five files:

.RS 5.0
- lex-definitions (lex specific definitions)
.br
- lex-syntax (cd-parse specific concrete syntax)
.br
- lex-comment (definition of comment sign)
.br
- lex-white-space (definition of white space)
.br
- lex-class-terminals (definition of syntax for terminal classes)
.RE

Any of the above files can be changed to customize the generic parser. If any
of the files are changed,
.I make
will automatically regenerate lex-DEM.l and subsequently lex.yy.c. Lex-syntax
depends on cd-parse which defines the concrete syntax for parsing object
descriptions. Therefore, in order to define a different object description
language customize cd-parse rather than lex-syntax directly. Once cd-parse is
changed, lex-syntax is automatically regenerated from cd-parse. Note that you
can protect your customized cd-parse from overriding by setting the
.I Imakefile
variable OVERWRITECDPARSE to "no". Even if OVERWRITECDPARSE is set to "yes",
Demeter will not discard your cd-parse but simply move it into cd-parse.old.

If
.I gen-scanner
is called explicitely, only lex-syntax is generated from cd-parse.

.RS 5.0
.I Example: 
In order to change the comment sign in object descriptions from '//' (default)
to '#', the file lex-comment has to be changed from:

.RS 5.0
"//"*$		;
.RE
.br
to:
.br
.RS 5.0
"#"*$		;
.RE
.RE

Then simply, type
.I make
to make the changes effective, and don't forget to change your object
descriptions. 

.SH SOURCE CODE 

The source is located at $DEMETER/bin.

.SH SEE ALSO

sem-check(1), generate(1), g_parse(2)

.SH REFERENCES 

.I User's Guide for the Demeter System C++
.br
Walter L. Hursch
.br
Northeastern University, 1993

.I The UNIX Programming Environment
.br
Brian W. Kernighan and Rob Pike
.br
Prentice Hall, 1984