| Title |
Creating a Lexical Analyzer in c |
| Author |
fahad bader al-buhairi �դ ?�� ��??��� |
| Author Email |
xxxq8xxx [at] hotmail.com |
| Description |
The token classes correspond to the following regular definitions , except and digit>, plus the class . (The ellipse ��� is used in the usual sense �and so on�. The spaces in the definitions are used for better adability, they are not valid parts of the definitions.)
::= ;
::= :
::= ,
::= + | - | * | /
::= < | <= | = | <> | >= | >
::= ( | )
::= % | ! | @ | ~ | $
::= a | A | b | B | � | z | Z
::= 0 | 1 | � | 9
::= ( | )*
::= + (. digit+ )? (E(+|-)?
The following lexemes should be recognized as keywords, not as
identifiers:
procedure, is, begin, end, var, cin, cout, if, then, else, and, or,
not,
loop, exit, when, while, until
The whitespace characters � � (space symbol) and
(end-of-line
symbol)
are to be skipped.
Comments (any text closed between braces �{� and �}� ) are to be
skipped
as well. The comments do not extend to several lines (they do not
contain
the end-of-line symbol).
The input for the lexical analyzer is a textfile SOURCE.TXT consisting
of
several lines of text (a �program�) being a correctly formed sequence
of
lexemes corresponding to the above definitions, whitespaces and
comments.
The output of your lexical analyzer consists of 2 text files ST.TXT and
TOKENS.TXT.
1. ST.TXT is the symbol table created by the lexical analyzer. Each
line
consists of three parts:
- line number
- the lexeme (string)
- type (string) , being one of the following: keyword, identifier, num
2. TOKENS.TXT is the list of tokens produced by the lexical analyzer
with
the following structure:
- one line of input (in the order of appearance in SOURCE.TXT)
- corresponding pairs �token, attribute�, each in a separate line in
the
order as they occur in the line
- blank line
The attribute of a keyword, identifier or a number is the line number
in
the symbol table. The attribute of any other token is the lexeme
itself.
The longest prefix of the input that can match any regular expression
pi
is taken as the next token. |
| Category |
C » Beginners / Lab Assignments |
| Hits |
510463 |
| Code |
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