Question $2$

Your task is to design and implement a lexical anlayzer for a programming language whose specifications are given below. The scanner identifies and outputs tokens $($valid words and punctuation$)$

in the source program. Its output is a token that can thereafter be used by the syntax analyzer to

verify that the program is syntactically valid. When called, the lexical analyzer should extract the

next token from the source program. The syntax of the language will be specified in TMA #$2.$

Punctuation Operators Reserved words

$($ ; $+<$ else integer self

$),>$ float let struct

$\{.*<=$ func private then

$\}$ : $/>=$ if public var

$[->=$ or impl read void

$]==$ and inherits return while

$<>$ not write

$1$

Lexical elements

id $->$ letter alphanum$$

letter $->$ a $...$ z $|$ A $...$ Z

alphanum $->$ letter $|$ digit $|\_$

digit $->0...9$

integer $->$ nonzero digit$$

$|0$

nonzero $->1...9$

float $->$ integer fraction $[$e $[+|]$ integer$]$

fraction $->.$ digit$$ nonzero $|\mathrm{.}0$

Comments:

$$ Inline comments start with $//$ and end with the end of the line they appear in$.$

$$ Block comments start with $/*$ and end with $*/$ and may span over multiple lines.

Answer to the following tasks:

$($a$)$ Identify the lexical specification, expressed as regular expressions, that you used in the design of the lexical analyzer.

$($Note: You should completely describe the data structure of your design and any changes

that you may have applied to the original lexical specifications should be also included.$)$

$($b$)$ Describe the complete operation of your lexical analyzer using finite state diagram.

$($c$)$ Write Lex $($and Yacc$)$ files to construct a lexical analyzer that recognizes the above$-$stated

tokens. It should be a function that returns a token data structure containing the information

about the next token identified in the source program file. The token data structure should

contains: $(1)$ the token type; $(2)$ the lexeme; and $(3)$ the location, of the token in the source

code.

$($Note: The parser that Yacc generates should be able to call the lexical analyzer generated by

Lex and perform parsing of the code generated by the given grammar. Your Lex file should

be able to remove any white space from the code. All correspondences should be stored in a

symbol table and printed out as output.$)$

$($d$)$ Identify all the possible lexical errors that the lexical analyzer might encounter and the possible error recovery techniques you could use. Choose one of them and discuss why you

have chosen it$.$

$($e$)$ Include many test cases that test a wide variety of valid and invalid cases