Programming Languages Project: Lexical Analyzer for Psi++
Lexical rules for the programming language Psi++ are as follows:
1- Identifiers:
- Maximum identifier size is 30 characters. If you use an identifier larger than that, the lexical analyzer issues an error message.
- Psi++ language is not case sensitive and all the identifier names are standardized as lower case.
- Identifiers start with an alphabetic character (a letter) and are composed of one or more letters/digits/_ (underscore)
- Example Token: Identifier(my_var_1)
2- Integer constants
- Maximum integer size is 10 digits. If you use an integer value longer than that, the lexical analyzer issues an error message.
- Negative values are not supported.
- Example Token: IntConst(1290)
3- Operators
- Valid operators of the language are +,-,*,/,++,--,:=
- Example Token: Operator(++)
4- Brackets
- LeftPar: (
- RightPar: )
- LeftSquareBracket: [
- RightSquareBracket: ]
- LeftCurlyBracket: {
- RightCurlyBracket: }
- Example Token: LeftCurlyBracket
5- String constants
- String constants of Psi++ are delimited by double quotes (ASCII code 34)as in “this is a string”
- String constants have unlimited size
- String constants cannot contain the double quote character. when you reach one, the string terminates.
- If a string constant cannot terminate before the file end, there should be a lexical error issued.
6- Keywords:
-
Keywords are: break,case,char,const,continue,do,else,enum,float,for,goto,if,int,long,record,return,static,while
-
Psi++ language is not case sensitive and all the keywords are standardized as lower case. You can write the same word as “while” OR “While” OR “WHILE” and they all generate the same thing.
-
Example Token: Keyword(while)
7- End of line: ;
- Example Token: EndOfLine
8- Comments: Anything between /* and */ is a comment.
- If a comment cannot terminate before the file end, there should be a lexical error issued.
- Comments are just like blank space and they provide no tokens.
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Project Definition:
Example:
if code.psi (example input text file name) contains:
hi:=hello+25; /*addition */
hello++; /*increment*/
code.lex would be:
Identifier(hi)
Operator(:=)
Identifier(hello)
Operator(+)
IntConst(25)
EndOfLine**
Identifier(hello)
Operator(++)
EndOfLine
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The Program accepts a source text file and produces a text file named as code.lex that contains all the tokens of the code.lex listed one after the other.
Run the program’s exe file from operating system’s console.
Example: PsiLexAnalyzer.exe code.psi