Tokens, patterns, and lexemes in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the basic unit of a programming language.

Compiler Design

A [1] is the smallest unit of a program that has a meaning.

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Atoken

Bpattern

Clexeme

Dsyntax

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing token with lexeme or pattern.

Thinking syntax is the smallest unit.

A token is the smallest meaningful unit in a programming language, such as keywords, identifiers, or symbols.

2fill in blank

medium

Complete the code to define the role of a pattern in token recognition.

Compiler Design

A [1] defines the rules or structure that a sequence of characters must follow to form a token.

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Alexeme

Bsyntax

Cpattern

Dgrammar

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing pattern with lexeme or syntax.

Thinking grammar defines token structure.

A pattern is a rule or description (often a regular expression) that defines how characters combine to form a token.

3fill in blank

hard

Fix the error in the statement about lexemes.

Compiler Design

A [1] is the actual sequence of characters in the source code that matches a pattern.

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Apattern

Blexeme

Csyntax

Dtoken

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up lexeme with token or pattern.

Thinking lexeme is a rule rather than actual text.

A lexeme is the actual text in the source code that matches a pattern and forms a token.

4fill in blank

hard

Fill both blanks to complete the dictionary comprehension that maps tokens to their lexemes if the lexeme length is greater than 3.

Compiler Design

{token: lexeme for token, lexeme in token_lexeme_list if len(lexeme) [1] 3 and token [2] 'IDENTIFIER'}

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A>

B==

C!=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than instead of greater than for length.

Using inequality instead of equality for token check.

The comprehension filters lexemes longer than 3 characters and tokens equal to 'IDENTIFIER'.

5fill in blank

hard

Fill all three blanks to create a dictionary of tokens and lexemes where lexemes start with a letter and tokens are not 'KEYWORD'.

Compiler Design

{ [1]: [2] for [3], lexeme in token_lexeme_pairs if lexeme[0].isalpha() and [3] != 'KEYWORD' }

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

Atoken

Blexeme

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping keys and values in the dictionary.

Using wrong variable names in the loop.

This comprehension creates a dictionary mapping tokens to lexemes where lexemes start with a letter and tokens are not keywords.