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UW-Madison CS 536 - final.f12

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CS 536Final ExamMonday, December 17, 20122:45 PM- 4:45 PM204 Educational SciencesAnswer any five questions. (If you answer more, only the first five will count.) Each question is worth 20 points. Please try to...1. Recall that in building parsers, the first relation is key in making parsing decisions. Define InFirst(A,a), where A is a non...2. Many programming languages allow method names to be overloaded. That is, the same identifier may be used to name several diff...3. Assume we have a CSX function whose header is4. Assume that we add a simple “for loop” to CSX:5. Recall that the JVM evaluates relational expressions like i==0 or a > b using a conditional branch. Show the code your CSX co...6. Consider the following three context-free grammars. Which are LL(1)? Why? Which are LALR(1)? Why?(i) S Æ A S S Æ b A Æ a A Æ l(ii) S Æ ( S ) S Æ [ S ] S Æ [ S ) S Æ a(iii) S Æ D P a D Æ b D Æ l P Æ c P Æ l7. Recall that in generating JVM code for methods we “guestimated” that a maximum stack depth of 25 would be sufficient. Give an...CS 536Final ExamMonday, December 17, 20122:45 PM— 4:45 PM204 Educational SciencesInstructionsAnswer any five questions. (If you answer more, only the first five will count.) Each question is worth 20 points. Please try to make your answers neat and coherent. Remember, if we can’t read it, it’s wrong. Partial credit will be given, so try to put something down for each question (a blank answer always gets 0 points!).1. Recall that in building parsers, the first relation is key in making parsing decisions. Define InFirst(A,a), where A is a nonterminal and a is a terminal, to be true if it is the case that A ⇒+ a…. (and false otherwise) That is, InFirst(A,a) tells us if a string of sym-bols beginning with the terminal symbol a may be derived from A. Give an algorithm that computes InFirst(A,a) given a grammar G.2. Many programming languages allow method names to be overloaded. That is, the same identifier may be used to name several different methods in the same scope as long as they can be distinguished at the point of call. Assume we allow CSX methods to be overloaded as long as each definition that shares the same name differs in the number of parameters it requires. Thus M() and M(x) and M(y,z) could all co-exist in the same class. Explain what changes you will need to make in your CSX symbol table and type checker modules to support this limited form of overloading. 3. Assume we have a CSX function whose header is int p(int a, int b) {… and a callz = p(1, p(2, p(4,5)));Show the JVM code you would generate for this call. Explain the steps the JVM interpreter performs to actually do the indicated function calls (parameter passing, frame manipulation, return address manipulation, etc.)-2-4. Assume that we add a simple “for loop” to CSX:for (id = init; condition)stmtid is any integer variable. init is an integer-valued expression that is evaluated at the beginning of the loop and assigned to id. condition is a boolean-valued expression that is evaluated at the start of each iteration. Iteration terminates as soon as condition becomes false. Zero iterations are possible. At the end of each itera-tion id is incremented by 1.Show the JVM code you’d generate for this kind of loop. Design an AST structure and code generator appropriate for this for loop. 5. Recall that the JVM evaluates relational expressions like i==0 or a > b using a condi-tional branch. Show the code your CSX compiler would generate to compute i != 5. Relational expressions are most commonly used in if statements and while loops. In the case of a statement like while (i!=5) { ... } it is probably the case that you com-pute i != 5 onto the stack (using a conditional branch) and then do a second condi-tional branch to decide whether to terminate the loop. A better approach would avoid directly computing a boolean onto the stack and instead use the conditional branch that implements i!=5 to also control loop termina-tion. Explain how you’d change your CSX compiler to implement this improved trans-lation scheme. What JVM code would you now generate for while (i!=5) { ... }?6. Consider the following three context-free grammars. Which are LL(1)? Why? Which are LALR(1)? Why?(i) S → A S S → b A → a A → λ (ii) S → ( S ) S → [ S ] S → [ S ) S → a (iii) S → D P a D → b D → λ P → c P → λ 7. Recall that in generating JVM code for methods we “guestimated” that a maximum stack depth of 25 would be sufficient. Give an example of a CSX program that requires a stack depth greater than 25. Rather than guessing at the stack depth we need, we should compute the needed stack depth directly. Outline how you’d compute this value as you are generating code for a method


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