Tema 040918

Pagina 1

Formal Languages and Compilers Proff. Breveglieri, Crespi Reghizzi, Morzenti Written exam1: laboratory question 04/09/2018 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 push- into and pop-from instructions that realize, respectively, the insertion and the extraction of a value into and from a stack, implemented by means of an array. Both the operators have two parameters: the array identifier and either an expression defining the value that is added to the stack in the push-into instruction or an identifier of a variable in the pop-from instruction. Beside the previous instructions, two operators are introduced for managing a stack: is-empty and is-full, both followed by the array identifier, return a boolean value indicating if the stack is empty of full, respectively. All the instructions raise an error if the array has not been declared or the identifier refers to a scalar. Assume that only one array identifier per program occurs as argument of a push-into and a pop-from and that the bottom of the stack is the position 0. Define a reasonable semantics for the instructions in case of misuse (e.g., pop with…