14 06 19

Page 1

FORMAL LANGUAGES AND COMPILERS prof.s Luca Breveglieri and Angelo Morzenti Exam of Fri14JUNE2019-P a r tT h e o r y WITH SOLUTIONS -FOR TEACHING PURPOSES HERE THE SOLUTIONS ARE WIDEL Y COMMENTED LAST + FIRST NAME: (capital letters please) MATRICOLA: SIGNATURE: (or PERSON CODE) INSTRUCTIONS - READ CAREFULLY: •The exam is in written form and consists of two parts: 1. Theory (80%): Syntax and Semantics of Languages –regular expressions and finite automata –free grammars and pushdown automata –syntax analysis and parsing methodologies –language translation and semantic analysis 2. Lab (20%): Compiler Design by Flex and Bison •To pass the exam, the candidate must succeed in both parts (th eory and lab), in one call or more calls separately, but within one year (12 months) between the two parts. •To pass part theory, the candidate must answer the mandatory (not optional) ques- tions; notice that the full grade is achieved by answering th e optional questions. •The exam is open book: textbooks and personal notes are permi tted. •Please write in the free space left and if necessary continue on the back side of the sheet; do not attach new sheets and do not replace the existin g ones. •Time: part lab 60m - part theory 2h.15m 1 Regular Expressions and Finite Automata 20% 1. Consider the two regular expressionse1ande2below: e1= ( (a|b)(c|d) )+ e2= ( (a|b)(b|c) )+ over the four-letter alphabet Σ ={a, b, c, d}. Answer the following questions: (a) By using the Berry-Sethi (BS) method, obtain two deterministic automata A1 andA2equivalent to the two above regular expressionse1ande2,r e s p e c t i v e l y . For each of the obtained automataA1andA2, say if it is minimal (explain why yes or no) and minimize it, if necessary. (b) Starting from automataA1andA2, build the product…