Podcast
Questions and Answers
Given the grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
and its corresponding parsing table. What action should the parser take when the stack contains 0 5 and the input is b?
Given the grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
and its corresponding parsing table. What action should the parser take when the stack contains 0 5 and the input is b?
- Reduce by rule 3 (r3)
- Reduce by rule 1 (r1)
- Shift to state 3 (s3)
- Shift to state 5 (s5) (correct)
Using the grammar and parsing table provided, what is the next state on the stack after performing a 'reduce by rule 1' action?
Using the grammar and parsing table provided, what is the next state on the stack after performing a 'reduce by rule 1' action?
- State 2
- State 1
- State 3
- State 4 (correct)
Consider the provided grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
If the parser reaches a state where the action table indicates 'accept', what does this signify?
Consider the provided grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
If the parser reaches a state where the action table indicates 'accept', what does this signify?
- The input string has been successfully parsed. (correct)
- The input string is syntactically incorrect.
- A reduction operation must be performed.
- The parser needs to shift the next input symbol.
Given the grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
What would be the appropriate action for a parser in state 3 with input 'a'?
Given the grammar:
0. S' -> S
1. S -> AB
2. A -> aA
3. A -> a
4. B -> bb
What would be the appropriate action for a parser in state 3 with input 'a'?
Consider the grammar:
S -> aSa
S -> B
B -> Bbb
B -> c
and a top-down parsing approach. Which of the following strings would present a challenge due to potential infinite recursion?
Consider the grammar:
S -> aSa
S -> B
B -> Bbb
B -> c
and a top-down parsing approach. Which of the following strings would present a challenge due to potential infinite recursion?
In the context of LR(1) parsing, what is the primary purpose of the 'lookahead' symbol?
In the context of LR(1) parsing, what is the primary purpose of the 'lookahead' symbol?
What is the key difference between LR(1) and LALR(1) parsing?
What is the key difference between LR(1) and LALR(1) parsing?
Given the grammar
S -> aSa
S -> B
B -> Bbb
B -> c
and considering only LR(1) parsing, what is the FIRST set of B?
Given the grammar
S -> aSa
S -> B
B -> Bbb
B -> c
and considering only LR(1) parsing, what is the FIRST set of B?
When constructing an LR(1) DFA, what does each state typically represent?
When constructing an LR(1) DFA, what does each state typically represent?
For the grammar:
S -> aSa
S -> B
B -> Bbb
B -> c
What is the FOLLOW set of S?
For the grammar:
S -> aSa
S -> B
B -> Bbb
B -> c
What is the FOLLOW set of S?
Flashcards
LR(1) Parsing
LR(1) Parsing
LR(1) parsing is a bottom-up parsing technique that uses one lookahead token to make parsing decisions.
Action and Goto Tables
Action and Goto Tables
A parsing table that guides the parser's actions based on the current state and the next input token.
Shift Action
Shift Action
An action in parsing where the parser consumes the next input token and moves to a new state.
Reduce Action
Reduce Action
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Parsing DFA
Parsing DFA
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LALR(1) Parsing
LALR(1) Parsing
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Study Notes
- This document provides practice problems for reviewing LR(1) parsing.
Grammar and Parsing Tables
- The grammar rules and corresponding action and goto tables is described
- S' → S (rule 0)
- S → AB (rule 1)
- A → aA (rule 2)
- A → a (rule 3)
- B → bb (rule 4)
Action Table Details
- State 0: shift to state 5 on input 'a'
- State 1: accept on input '$'
- State 2: shift to state 3 on input 'a'
- State 3: shift to state 7 on input 'a'
- State 4: reduce using rule 1
- State 5: shift to state 5 on input 'a', reduce using rule 3 on input 'b'
- State 6: reduce using rule 2
- State 7: reduce using rule 4
Goto Table Details
- From state 0, go to state 1 on S, state 2 on A
- From state 2, go to state 4 on B
- From state 5, go to state 6 on B
Parsing Task
- Create a table showing the stack, input, and action at each step of parsing the string "aaabb", following the format on slide 39 of the lexing and parsing lectures.
LR(1) DFA
- Draw the LR(1) parsing DFA (following slide 55) for the provided grammar:
- S → aSa (rule 1)
- S → B (rule 2)
- B → Bbb (rule 3)
- B → c (rule 4)
LALR(1) DFA
- Draw the LALR(1) parsing DFA for the grammar.
- Determine if switching from LR(1) to LALR(1) parsing introduces any parsing conflicts.
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