Virtual Labs

Demonstration of Ambiguity in Context-Free Grammars

How can you prove that a context-free grammar is ambiguous?

a: Show that it has recursive production rules Explanation

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b: Show that it generates an infinite language Explanation

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c: Show two different parse trees for the same string Explanation

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d: Show that it has multiple production rules for one non-terminal Explanation

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What is the practical significance of ambiguity in programming language grammars?

a: It makes programs run faster Explanation

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b: It can lead to different interpretations of the same code Explanation

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c: It reduces memory usage Explanation

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d: It simplifies compiler design Explanation

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In the context of ambiguous grammars, what do multiple derivations of the same string demonstrate?

a: The grammar is incorrect Explanation

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b: The string doesn't belong to the language Explanation

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c: Different structural interpretations of the same input Explanation

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d: The need for more production rules Explanation

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For the expression 'a + b * c', why might different parse trees lead to different results?

a: Because the variables have different values Explanation

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b: Because the operations are performed in different orders Explanation

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c: Because the expression syntax is invalid Explanation

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d: Because different compilers are used Explanation

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In the string concatenation grammar S → SS | ab | ba, what does the ambiguity of 'abab' reveal about associativity?

a: Concatenation is always left-associative Explanation

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b: Concatenation is always right-associative Explanation

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c: The grammar doesn't specify associativity for concatenation Explanation

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d: Associativity is irrelevant for concatenation Explanation

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What makes the dangling else problem particularly challenging in compiler design?

a: It requires special hardware support Explanation

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b: It affects program semantics based on parser choice Explanation

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c: It only occurs in functional programming languages Explanation

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d: It makes programs syntactically invalid Explanation

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If a grammar generates the string 'if E then if E then other else other' with two different parse trees, what are the two possible interpretations?

a: Sequential execution vs. parallel execution Explanation

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b: Compile-time evaluation vs. runtime evaluation Explanation

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c: Else belongs to outer if vs. else belongs to inner if Explanation

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d: Forward execution vs. backward execution Explanation

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How would you resolve the ambiguity in the arithmetic expression grammar E → E + E | E * E | (E) | id?

a: Remove the problematic operators Explanation

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b: Introduce precedence through separate non-terminals Explanation

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c: Add more parentheses to all expressions Explanation

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d: Use only left-recursive rules Explanation

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When comparing two derivations of the same string in an ambiguous grammar, what fundamental property are you observing?

a: The grammar's computational complexity Explanation

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b: The string's membership in the language Explanation

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c: The non-deterministic nature of grammatical parsing Explanation

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d: The grammar's generative capacity Explanation

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