CS 401/501 Exam: Tokens vs Lexemes, RegEx, BNF Grammar, Parsing & Attribute Grammar, Exams of Programming Languages

Download CS 401/501 Exam: Tokens vs Lexemes, RegEx, BNF Grammar, Parsing & Attribute Grammar and more Exams Programming Languages in PDF only on Docsity! CS 401/501 EXAM #1 SAMPLE QUESTIONS 1. Explain the difference between a token and a lexeme. (5%) 2. For each regular expression below provide a brief description what kind of lexemes are going to match with a pattern and provide some examples of lexemes (at least 3). [pr]?ink [a-z][a-z0-9]* [1-9][0-9][0-9] /\*[^\*]+\*/ ([a-c][0-9])+ (10%) 3. Write a BNF grammar for a language, in which programs always start with the keyword “print” followed by arithmetic expression (+ or -). The later is optionally followed by a declaration part, starting with the keyword “where” and a list of pairs “id=num” which are separated with “,”. Few examples: print 10 print a+10 where a=1 print a+b-c where a=2, b=4, c=21 (20%) 4. Perform left factoring on the production B ::= spring A | spring num C (5%) 5. Write a recursive descent parser for the following LL(1) grammar. Assume the existence of a scanning procedure GET_TOKEN which sets a global string variable TOKEN to the token type of the next token. P ::= D begin S end D ::= var V V::= T V | ε T ::= int id ; | real id ; S ::= id := num S | ε Draw a parse tree for the sentence: var int i; int j; begin end (25+5%) 6. Write an attribute grammar for a following grammar: Eq ::= Sum = Sum Sum ::= Prod AddOp Sum | Prod Prod ::= Fact MulOp Prod | Fact Fact ::= ( Sum ) | num AddOp ::= + | - MulOp ::= * | /