Implementing a lexical analyzer in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the function that starts the lexical analysis.

Compiler Design

def [1](source_code):

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

Alexical_analyzer

Btokenize

Cparse

Dcompile

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parse' which is for syntax analysis, not lexical analysis.

Using 'compile' which is for the whole compilation process.

The function that begins the lexical analysis is commonly called lexical_analyzer or similar, as it processes the source code into tokens.

2fill in blank

medium

Complete the code to read the next character from the source code string.

Compiler Design

current_char = source_code[[1]]

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

A0

Bindex

Clength

Dtoken

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0' which always reads the first character, not the current one.

Using 'token' which is unrelated to string indexing.

The variable index is typically used to track the current position in the source code string to read characters one by one.

3fill in blank

hard

Fix the error in the condition to check if the current character is a digit.

Compiler Design

if current_char [1] '0' and current_char [2] '9':

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

A>=

B<=

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which only checks equality to one character.

Using '!=' which checks inequality, not range.

To check if a character is a digit, it must be greater than or equal to '0' and less than or equal to '9'.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps tokens to their types for all tokens longer than 2 characters.

Compiler Design

token_types = {token: [1] for token in tokens if len(token) [2] 2}

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

A'identifier'

B>

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' which limits tokens to length exactly 2.

Using '<' which selects tokens shorter than 2 characters.

The dictionary maps each token to the string 'identifier' if its length is greater than 2.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase tokens to their lengths if length is at least 3.

Compiler Design

result = { [1]: [2] for [3] in tokens if len([3]) >= 3 }

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

Atoken.upper()

Blen(token)

Ctoken

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Not converting the token to uppercase for the key.

The comprehension maps each token converted to uppercase (token.upper()) to its length (len(token)) for tokens named token with length at least 3.