hw3 - * x + 1 else if ( b == 0) then x = 3 * x + 2 else x =...

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VERSION: September 16, 2010 CS-441 Fall 2010 JWJ CS UK Homework Assignment # 3 —This material is only for use in CS441-Fall 2010 in the Department of Computer Science at the University of Kentucky.— —Please, do not distribute.— Due: solve by Thursday, Sep 23, 2010 Learning outcomes: This assignments relates to the material on CFG grammars and their properties. The assignment contributes to the following learning outcomes for this course: LO2 specify parsing elements for algorithmic languages LO4 design and implement a complete algorithmic language compiler hw 3.1: Consider the following two CF grammars: < Stmt > ::= if < Expr > then < Stmt > | if < Expr > then < Stmt > else < Stmt > | < other stmts > < Stmt > ::= if < Expr > then < Stmt > | if < Expr > then < IElse > else < Stmt > | < other stmts > < IElse > ::= if < Expr > then < IElse > else < IElse > | < other stmts > Table 1: Grammar G 1 (left) and G 2 (right) 3.1.1 (a) Consider the following statement: if ( a == 0) then x = 3
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Unformatted text preview: * x + 1 else if ( b == 0) then x = 3 * x + 2 else x = 3 * x-1. When E is written in place of Boolean expressions and S is written in place of statements, this can be written as if (E1) then S1 else if (E2) then S2 else S3. Show a parse tree for this statement using grammar G 1 . (b) Draw two dierent parse trees for grammar G 1 and string if (E1) then if (E2) then S2 else S3. 3.1.2 Draw a parse tree for the same string if (E1) then if (E2) then S2 else S3 using grammar G 2 . 3.1.3 Answer the following questions: Is the grammar G 1 ambiguous? Explain. Which of the two trees generated with grammar G 1 correspond to the meaning of the statement in a typical programming language (such as C++)? Is grammar G 2 ambiguous? How could you justify your answer? 1...
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This document was uploaded on 12/14/2010.

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