Syntax tree representation in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a node representing an operator in a syntax tree.

Compiler Design

node = SyntaxTreeNode(value=[1])

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

A"+"

B"operand"

C"statement"

D"function"

Attempts:

3 left

💡 Hint

Common Mistakes

Using operand or statement as the node value instead of the operator symbol.

The value of a syntax tree node representing an operator should be the operator symbol, such as "+".

2fill in blank

medium

Complete the code to add a left child node to the current syntax tree node.

Compiler Design

current_node.left = [1]

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

ASyntaxTreeNode(value="+")

BSyntaxTreeNode(value="operand")

CSyntaxTreeNode(value="-")

DSyntaxTreeNode(value="statement")

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a string directly instead of a SyntaxTreeNode object.

The left child node can be another operator node, such as "+" in this example.

3fill in blank

hard

Fix the error in the code that creates a syntax tree node with two children.

Compiler Design

node = SyntaxTreeNode(value="*", left=[1], right=[2])

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

ASyntaxTreeNode(value="+")

BSyntaxTreeNode(value="operand")

CSyntaxTreeNode(value="-")

DSyntaxTreeNode(value="statement")

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for left and right children causing type errors.

Both left and right children should be valid syntax tree nodes. Using the same operator node "+" for both children is correct here.

4fill in blank

hard

Fill both blanks to create a dictionary representing a syntax tree with node values and their children.

Compiler Design

syntax_tree = {"root": [1], "children": [2]

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

A"*"

B["+", "-"]

C["operand1", "operand2"]

D"root_node"

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings instead of lists for children or incorrect root values.

The root node value is "*" and its children are the list ["+", "-"] representing operator nodes.

5fill in blank

hard

Fill all three blanks to complete the syntax tree node creation with value, left child, and right child.

Compiler Design

node = SyntaxTreeNode(value=[1], left=[2], right=[3])

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

A"-"

BSyntaxTreeNode(value="operand1")

CSyntaxTreeNode(value="operand2")

DSyntaxTreeNode(value="+")

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings instead of SyntaxTreeNode objects for children.

The node value is "-", with left child operand1 and right child operand2 as syntax tree nodes.

Practice

1. What is the main purpose of a syntax tree in compiler design?

easy

A. To manage memory allocation during runtime

B. To execute the program directly

C. To represent the structure of source code clearly

D. To store compiled machine code

Solution

1. Step 1: Understand the role of syntax trees

   Syntax trees break down source code into parts showing its structure clearly.

2. Step 2: Compare with other compiler tasks

   Execution, machine code storage, and memory management are handled by other compiler stages, not syntax trees.

3. Final Answer:

   To represent the structure of source code clearly -> Option C

4. Quick Check:

   Syntax tree = code structure [OK]

Hint: Syntax trees show code parts and structure clearly [OK]

Common Mistakes:

• Confusing syntax tree with execution or memory management
• Thinking syntax trees store machine code
• Assuming syntax trees run the program

2. Which of the following is the correct way to represent the expression a + b * c in a syntax tree?

easy

A. Root node '+' with left child 'a' and right child '*' having children 'b' and 'c'

B. Root node '*' with left child '+' and right child 'c', '+' having children 'a' and 'b'

C. Root node '+' with children 'a', 'b', and 'c' directly

D. Root node 'a' with children '+' and '*'

Solution

1. Step 1: Recall operator precedence

   Multiplication (*) has higher precedence than addition (+), so '*' is evaluated before '+'.

2. Step 2: Build the tree respecting precedence

   The root is '+', left child is 'a', right child is '*', which has 'b' and 'c' as children.

3. Final Answer:

   Root node '+' with left child 'a' and right child '*' having children 'b' and 'c' -> Option A

4. Quick Check:

   Operator precedence guides tree structure [OK]

Hint: Remember operator precedence to build syntax trees [OK]

Common Mistakes:

• Ignoring operator precedence and ordering nodes incorrectly
• Placing all operands as direct children of root
• Confusing node roles and children

3. Given the syntax tree for the expression (x - y) / z, what is the correct preorder traversal output?

medium

A. - / x y z

B. / - x y z

C. / x - y z

D. - x y / z

Solution

1. Step 1: Understand preorder traversal

   Preorder visits root first, then left subtree, then right subtree.

2. Step 2: Apply preorder to the tree

   Root is '/', left child is '-', with children 'x' and 'y', right child is 'z'. So traversal is '/ - x y z'.

3. Final Answer:

   / - x y z -> Option B

4. Quick Check:

   Preorder = root-left-right [OK]

Hint: Preorder = root, left, right traversal order [OK]

Common Mistakes:

• Mixing traversal orders (inorder, postorder)
• Visiting children before root in preorder
• Confusing node positions in tree

4. Identify the error in this syntax tree representation of the expression a + (b * c: The tree has '+' as root, 'a' as left child, and '*' as right child with children 'b' and 'c'.

medium

A. Operator '*' should be root instead of '+'

B. The tree correctly represents the expression

C. Operands 'b' and 'c' should be swapped

D. Missing closing parenthesis causes incomplete tree

Solution

1. Step 1: Check expression syntax

   The expression has an opening parenthesis '(' but no closing ')', making it incomplete.

2. Step 2: Analyze tree correctness

   The tree structure matches the intended expression but the missing ')' means the expression is invalid, so the tree is incomplete.

3. Final Answer:

   Missing closing parenthesis causes incomplete tree -> Option D

4. Quick Check:

   Unmatched parentheses cause syntax tree errors [OK]

Hint: Check parentheses balance before building syntax tree [OK]

Common Mistakes:

• Assuming tree is correct despite syntax errors
• Confusing operator precedence with syntax errors
• Ignoring unmatched parentheses

5. How would you represent the nested expression (a + b) * (c - d) as a syntax tree to correctly reflect operator precedence and grouping?

hard

A. Root '*' with left child '+' (children 'a', 'b') and right child '-' (children 'c', 'd')

B. Root '+' with children 'a', 'b', '*', 'c', 'd'

C. Root '-' with left child '*' and right child '+'

D. Root '*' with children 'a', 'b', 'c', 'd' directly

Solution

1. Step 1: Identify operator precedence and grouping

   Parentheses force addition and subtraction to happen before multiplication.

2. Step 2: Build tree respecting groups

   Root is '*', left subtree is '+' with 'a' and 'b', right subtree is '-' with 'c' and 'd'.

3. Final Answer:

   Root '*' with left child '+' (children 'a', 'b') and right child '-' (children 'c', 'd') -> Option A

4. Quick Check:

   Parentheses define subtree grouping in syntax tree [OK]

Hint: Use parentheses to group subtrees in syntax tree [OK]

Common Mistakes:

• Ignoring parentheses and operator precedence
• Placing all operands as direct children of root
• Mixing operator positions in tree