An Example of Lex
This is a very simple example of how to use Lex.
The file ex.lex contains rules that match all
five letter words that begin with a "p" and end with a "t".
(This might be useful in solving a crossword puzzle!).
Lex takes the specification and produces a file "lex.yy.c"
that contains a subroutine "yylex()".
This subroutine is called from main.c.
Each time yylex() returns a word that matches our requirement,
it is printed.
When the entire input has been scanned, "yywrap()" is called by
yylex().
This sets a flag indicating that we are done.