Note: In your documentation (design section), YOU MUST write the REs for Identifiers, Real and Integer, and also show the NFSM using Thompson.
The Lexer
A major component of your assignment will be to write a procedure (Function) – lexer (), that returns a token when it is needed. Your lexer() should return a record, one field for the token and another field the actual "value" of the token (lexeme), i.e. the instance of a token.
Your main program should test the lexer i.e., your program should read a file containing the source code given from class to generate tokens and write out the results to an output
file . Make sure that you print both, the tokens and lexemes.
Basically, your main program should work as follows while not finished (i.e. not end of the source file) do
call the lexer for a token
print the token and lexeme
endwhile
Do at least 3 test cases and make sure that you turn in proper documentation using the documentation template.
A simple test case
(Partial) Source code:
while (fahr < upper) a = 23.00 whileend
Output:
token
lexeme
keyword
while
separator
(
identifier
fahr
operator
<
identifier
upper
separator
)
identifier
a
operator
=
real
23.00
keyword
whileend
