Type checking rules in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the type of a variable in a simple type checking rule.

Compiler Design

if variable.type == [1]:
    print("Variable is an integer")

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

A"int"

B"bool"

C"string"

D"float"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong type string like "float" or "string" instead of "int".

The type checking rule compares the variable's type to the string "int" to confirm it is an integer.

2fill in blank

medium

Complete the code to check if two variables have the same type before assignment.

Compiler Design

if var1.type == var2.[1]:
    var1.value = var2.value

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

Atype

Bvalue

Cname

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing values or names instead of types.

To ensure type safety, the code compares the types of both variables before assignment.

3fill in blank

hard

Fix the error in the type checking condition to allow only boolean variables.

Compiler Design

if variable.type == [1]:
    print("Variable is boolean")

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

A"Bool"

B"boolean"

C"bool"

D"BOOLEAN"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "boolean" or capitalized versions which are not standard type names.

The correct type string for boolean variables is "bool" in most languages and type checkers.

4fill in blank

hard

Fill both blanks to create a type checking rule that allows assignment only if the source type is compatible with the target type.

Compiler Design

if source.type [1] target.type or target.type == [2]:
    assign(source, target)

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

A==

B!=

C"any"

D"void"

Attempts:

3 left

💡 Hint

Common Mistakes

Using inequality instead of equality, or wrong special type names.

The rule allows assignment if types are equal or if the target type is "any", meaning it accepts any type.

5fill in blank

hard

Fill all three blanks to define a type checking rule that filters variables by type and value condition.

Compiler Design

filtered_vars = {var: var.[1] for var in variables if var.[2] [3] 10}

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

Atype

Bvalue

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong properties or comparison operators that do not filter correctly.

This dictionary comprehension selects variables by their type and filters those with values greater than 10.

Practice

1. What is the main purpose of type checking rules in a compiler?

easy

A. To ensure that data types are used correctly in operations and assignments

B. To optimize the program's execution speed

C. To translate code into machine language

D. To manage memory allocation during runtime

Solution

1. Step 1: Understand the role of type checking

   Type checking rules verify that variables and expressions use compatible data types to avoid errors.

2. Step 2: Differentiate from other compiler tasks

   Optimization, translation, and memory management are separate compiler tasks, not type checking.

3. Final Answer:

   To ensure that data types are used correctly in operations and assignments -> Option A

4. Quick Check:

   Type checking = Correct data types [OK]

Hint: Type checking = matching data types in code [OK]

Common Mistakes:

• Confusing type checking with code optimization
• Thinking type checking manages memory
• Assuming type checking translates code

2. Which of the following is a correct type checking rule for assignment statements?

easy

A. Type checking only applies to function calls, not assignments

B. A variable can be assigned a value of any type without restrictions

C. Variables do not need to be declared before assignment

D. The type of the value assigned must match the variable's declared type

Solution

1. Step 1: Review assignment type rules

   In type checking, the value assigned must have the same type as the variable's declared type.

2. Step 2: Eliminate incorrect options

   Allowing any type or ignoring declarations violates type safety; type checking applies to assignments.

3. Final Answer:

   The type of the value assigned must match the variable's declared type -> Option D

4. Quick Check:

   Assignment types must match [OK]

Hint: Assignment value type = variable type [OK]

Common Mistakes:

• Ignoring variable declarations
• Assigning incompatible types
• Thinking type checking excludes assignments

3. Consider this code snippet:

int x = 5;
float y = 3.2;
x = y;

What will a strict type checker report?

medium

A. No error, assignment allowed

B. Warning but allowed at runtime

C. Type mismatch error: cannot assign float to int

D. Syntax error due to missing semicolon

Solution

1. Step 1: Identify variable types and assignment

   Variable x is int, y is float. Assignment tries to put a float into an int.

2. Step 2: Apply strict type checking rules

   Strict type checking disallows assigning a float value to an int variable without explicit conversion.

3. Final Answer:

   Type mismatch error: cannot assign float to int -> Option C

4. Quick Check:

   Float to int assignment = error [OK]

Hint: Assigning float to int causes type mismatch error [OK]

Common Mistakes:

• Assuming implicit conversion is automatic
• Confusing syntax errors with type errors
• Ignoring strict type checking rules

4. Identify the error in this code snippet under type checking rules:

string name = "Alice";
int age = "30";

medium

A. No error, both assignments are valid

B. Type error: assigning string literal to int variable

C. Syntax error: missing quotes around 30

D. Runtime error due to invalid conversion

Solution

1. Step 1: Analyze variable declarations and assignments

   name is a string assigned a string literal, which is correct. age is an int assigned a string literal "30".

2. Step 2: Apply type checking rules

   Assigning a string literal to an int variable violates type checking rules, causing a type error.

3. Final Answer:

   Type error: assigning string literal to int variable -> Option B

4. Quick Check:

   String to int assignment = type error [OK]

Hint: Assigning string to int causes type error [OK]

Common Mistakes:

• Thinking quotes around 30 are optional
• Confusing syntax errors with type errors
• Assuming implicit conversion from string to int

5. Given a function with parameters typed as int and float, which call violates type checking rules?

void process(int a, float b) { /*...*/ }

// Calls:
process(10, 5.5);
process(3.2, 4.1);
process(7, 2);

hard

A. process(3.2, 4.1);

B. process(10, 5.5);

C. process(7, 2);

D. All calls are valid

Solution

1. Step 1: Check parameter types for each call

   Function expects int then float. Call 1 passes int and float correctly. Call 2 passes float then float, which mismatches first parameter. Call 3 passes int and int, which may be allowed if int converts to float.

2. Step 2: Apply strict type checking

   Call 2 violates type checking because first argument is float but expected int. Call 3 is valid if implicit int to float conversion allowed for second parameter.

3. Final Answer:

   process(3.2, 4.1); -> Option A

4. Quick Check:

   First param must be int, call 2 fails [OK]

Hint: First argument must be int, float causes error [OK]

Common Mistakes:

• Assuming all numeric types are interchangeable
• Ignoring parameter order in function calls
• Thinking int cannot convert to float