Context-free grammars in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple production rule in a context-free grammar.

Compiler Design

S -> [1]

Drag options to blanks, or click blank then click option'

A"aSb"

B"a"

C"ab"

D"b"

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a string with multiple symbols which is not a single production.

Using non-terminal symbols on the right side without proper notation.

The production rule S -> "a" defines that the start symbol S can be replaced by the terminal symbol a. This is a basic example of a context-free grammar rule.

2fill in blank

medium

Fill both blanks to show a recursive production rule for balanced parentheses.

Compiler Design

P -> [1] P [2] | ""

Drag options to blanks, or click blank then click option'

A"["

B"("

C"{"

D")"

Attempts:

3 left

💡 Hint

Common Mistakes

Using mismatched parentheses symbols.

Forgetting the empty string alternative.

The rule P -> "(" P ")" | "" defines balanced parentheses recursively. The symbol P can be replaced by an opening parenthesis, followed by P, then a closing parenthesis, or by the empty string.

3fill in blank

hard

Fix the error in the production rule for arithmetic expressions.

Compiler Design

E -> E [1] T | T

Drag options to blanks, or click blank then click option'

A"+"

B"-"

C"*"

D"/"

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication or division instead of addition.

Using an operator that does not fit the grammar rule.

The production rule E -> E + T | T correctly defines addition in arithmetic expressions. The symbol E can be replaced by E + T or just T. Using + here models addition.

4fill in blank

hard

Fill both blanks to complete the production rule for identifiers starting with a letter followed by letters.

Compiler Design

ID -> [1] | [1] [2]

Drag options to blanks, or click blank then click option'

Aletter

B"digit"

CID

D"number"

Attempts:

3 left

💡 Hint

Common Mistakes

Using digits as the first symbol.

Not using recursion to allow multiple characters.

The rule ID -> letter | letter ID defines an identifier starting with a letter followed by zero or more letters. This recursive definition allows building identifiers of any length.

5fill in blank

hard

Fill all three blanks to define a production rule for a simple if-statement.

Compiler Design

Stmt -> "if" [1] "then" [2] [3]

Drag options to blanks, or click blank then click option'

Acondition

BStmt

C"else"

Dexpression

Attempts:

3 left

💡 Hint

Common Mistakes

Using "expression" instead of "condition".

Omitting the "else" keyword.

The production rule Stmt -> "if" condition "then" Stmt "else" Stmt models a simple if-then-else statement. The condition is checked, then a statement is executed, optionally followed by an else clause.