Unit LexLib

Classes

Functions

echo - write one character to the output file *) (* Utility routines:

Utilities:
get_char - I/O routines: The following routines get_char, unget_char and put_char are used to implement access to the input and output files.
put_char - return one character to the input file to be reread in subsequent calls to get_char

unget_char
reject - truncate yytext to size n and return the remaining characters to the input stream

yyless
return - reject the current match and execute the next one *) (* reject does not actually cause the input to be rescanned; instead, internal state information is used to find the next match.
returnc - return
start - sets the return value of yylex

returnc
unget_char - obtain one character from the input file (null character at end-of- file)

get_char
yyclear - executes the default action (copy character); returns true unless at end-of-file

yydefault
yydefault - finds the last match and the corresponding marked position and adjusts the matched string accordingly; returns: - true if a rule has been matched, false otherwise - n: the number of the matched rule

yyfind
yyfind - declares a match for rule number n

yymatch
yyless - append the next match to the current one

yymore
yymark - gets next character from the input stream and updates yytext and yyactchar accordingly

yyscan
yymatch - marks position for rule no.
yymore - echoes the current match to the output stream

echo
yynew - yylex return value

Internal routines:
yyscan - starts next match; initializes state information of the lexical analyzer

yynew
yywrap - puts the lexical analyzer in the given start state; state=0 denotes the default start state, other values are user-defined *) (* yywrap: The yywrap function is called by yylex at end-of-file (unless you have specified a rule matching end-of-file).

Types

Constants

Variables

yyactchar
yycolno
yydone
yyinput
yylastchar
yyleng
yyline
yylineno
yyoutput
yyreject
yyretval
yyrule
yystate
yytext


Functions


procedure echo;

write one character to the output file *) (* Utility routines:

Utilities:


function get_char : Char;

I/O routines: The following routines get_char, unget_char and put_char are used to implement access to the input and output files. Since \n (newline) for Lex means line end, the I/O routines have to translate MS-DOS line ends (carriage-return/line-feed) into newline characters and vice versa. Input is buffered to allow rescanning text (via unput_char). The input buffer holds the text of the line to be scanned. When the input buffer empties, a new line is obtained from the input stream. Characters can be returned to the input buffer by calls to unget_char. At end-of- file a null character is returned. The input routines also keep track of the input position and set the yyline, yylineno, yycolno variables accordingly. Since the rest of the Lex library only depends on these three routines (there are no direct references to the yyinput and yyoutput files or to the input buffer), you can easily replace get_char, unget_char and put_char by another suitable set of routines, e.g. if you want to read from/write to memory, etc.

newline character


procedure put_char ( c : Char );

return one character to the input file to be reread in subsequent calls to get_char

unget_char


procedure reject;

truncate yytext to size n and return the remaining characters to the input stream

yyless


procedure return ( n : Integer );

reject the current match and execute the next one *) (* reject does not actually cause the input to be rescanned; instead, internal state information is used to find the next match. Hence you should not try to modify the input stream or the yytext variable when rejecting a match.

reject


procedure returnc ( c : Char );

return

procedure start ( state : Integer );

sets the return value of yylex

returnc


procedure unget_char ( c : Char );

obtain one character from the input file (null character at end-of- file)

get_char


procedure yyclear;

executes the default action (copy character); returns true unless at end-of-file

yydefault


function yydefault : Boolean;

finds the last match and the corresponding marked position and adjusts the matched string accordingly; returns: - true if a rule has been matched, false otherwise - n: the number of the matched rule

yyfind


function yyfind ( var n : Integer ) : Boolean;

declares a match for rule number n

yymatch


procedure yyless ( n : Integer );

append the next match to the current one

yymore


procedure yymark ( n : Integer );

gets next character from the input stream and updates yytext and yyactchar accordingly

yyscan


procedure yymatch ( n : Integer );

marks position for rule no. n

yymark


procedure yymore;

echoes the current match to the output stream

echo


procedure yynew;

yylex return value

Internal routines:


procedure yyscan;

starts next match; initializes state information of the lexical analyzer

yynew


function yywrap : Boolean;

puts the lexical analyzer in the given start state; state=0 denotes the default start state, other values are user-defined *) (* yywrap: The yywrap function is called by yylex at end-of-file (unless you have specified a rule matching end-of-file). You may redefine this routine in your Lex program to do application-dependent processing at end of file. In particular, yywrap may arrange for more input and return false in which case the yylex routine resumes lexical analysis.

yywrap:


Types


Constants


Variables

yyactchar : Char

current state of lexical analyzer

yycolno : Integer

yydone : Boolean

current match rejected?

yyinput : Text

The Lex library unit supplies a collection of variables and routines needed by the lexical analyzer routine yylex and application programs using Lex-generated lexical analyzers. It also provides access to the input/output streams used by the lexical analyzer and the text of the matched string, and provides some utility functions which may be used in actions. This `standard' version of the LexLib unit is used to implement lexical analyzers which read from and write to MS-DOS files (using standard input and output, by default). It is suitable for many standard applications for lexical analyzers, such as text conversion tools or compilers. However, you may create your own version of the LexLib unit, tailored to your target applications. In particular, you may wish to provide another set of I/O functions, e.g., if you want to read from or write to memory instead to files, or want to use different file types. *) (* Variables: The variable yytext contains the current match, yyleng its length. The variable yyline contains the current input line, and yylineno and yycolno denote the current input position (line, column). These values are often used in giving error diagnostics (however, they will only be meaningful if there is no rescanning across line ends). The variables yyinput and yyoutput are the text files which are used by the lexical analyzer. By default, they are assigned to standard input and output, but you may change these assignments to fit your target application (use the Turbo Pascal standard routines assign, reset, and rewrite for this purpose).

yylastchar : Char

current character

yyleng : Byte (* length of matched text *) absolute yytext

matched text (should be considered r/o)

yyline : String

input and output file

yylineno : Integer

current input line

yyoutput : Text

yyreject : Boolean

matched rule

yyretval : Integer

yylex return value set?

yyrule : Integer

last matched character (#0 if none)

yystate : Integer

The default yywrap routine supplied here closes input and output files and returns true (causing yylex to terminate). *) (* The following are the internal data structures and routines used by the lexical analyzer routine yylex; they should not be used directly.

yytext : String

current input position