Tema 030718

Pagina 1

Formal Languages and Compilers Proff. Breveglieri, Morzenti Written exam1: laboratory question 03/07/2018 SURNAME: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NAME: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Student ID:. . . . . . . . . . . . . . . . Course: ◦ Laurea Specialistica ◦ V. O. ◦ Laurea Triennale ◦ Other: . . . . . . . . . . . . . Instructor: ◦ Prof. Breveglieri ◦ Prof Morzenti The laboratory question must be answered taking into account the implementation of the Acse compiler given with the exam text. Modify the specification of the lexical analyser ( flex input) and the syntactic analyser (bison input) and any other source file required to extend the Lance language with the new alias construct. The alias construct defines a code block where a variable acts as an alias for another one. Consider the following example. int a,b,c; a=3; b=5; c=7; alias a b { a=a+1-c; } write(a); write(b); The example at hand employs the alias construct to define a as an alias for b within the code block following b. This implies that any action (definition or use) of a in the code block indeed ends up acting on b. In the example the two write statements will cause the printout of 3 and −1 respectively, as a is not modified, while b is as an effect of the aliasing. The alias construct cannot be nested; such a syntax error should prevent the compilation of the program. 1Time 60’. Textbooks and notes can be used. Pencil writing is allowed. Write your name on any additional sheet. 1 1. Define the tokens (and the related declarations in Acse.lex and Acse.y). (3 points) 2. Define the syntactic rules or the modifications required to the…