Bitwise operators in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the bitwise AND operator (&) do in Rust?

It compares each bit of two numbers and returns a new number where each bit is 1 only if both bits in the original numbers were 1; otherwise, the bit is 0.

beginner

Explain the bitwise OR operator (|) in Rust.

It compares each bit of two numbers and returns a new number where each bit is 1 if at least one of the bits in the original numbers was 1; otherwise, the bit is 0.

beginner

What is the purpose of the bitwise XOR operator (^) in Rust?

It compares each bit of two numbers and returns a new number where each bit is 1 if the bits are different (one is 1 and the other is 0); if the bits are the same, the bit is 0.

beginner

How does the bitwise NOT operator (~) work in Rust?

It flips every bit of a number: all 1 bits become 0, and all 0 bits become 1. Note: In Rust, the bitwise NOT operator is ~, not !.

intermediate

What do the left shift (<<) and right shift (>>) operators do in Rust?

Left shift (<<) moves all bits in a number to the left by a specified number of places, adding zeros on the right. Right shift (>>) moves bits to the right, discarding bits on the right and filling in on the left depending on the type.

What is the result of 5 & 3 in Rust? (5 = 0101, 3 = 0011 in binary)

A 0

B 1

C 6

D 7

Bitwise AND compares bits: 0101 & 0011 = 0001, which is 1 in decimal.

Which operator flips all bits of a number in Rust?

A ~

B |

C &

D ^

The ~ operator is the bitwise NOT operator that flips all bits.

What does the expression 4 << 1 evaluate to in Rust?

A 8

B 2

C 5

D 1

Left shifting 4 (0100) by 1 bit gives 1000, which is 8.

Which bitwise operator returns 1 only if bits are different?

A &

B |

C ~

D ^

The XOR (^) operator returns 1 when bits differ.

What is the result of 7 | 2 in Rust? (7 = 0111, 2 = 0010 in binary)

A 5

B 3

C 7

D 2

Bitwise OR: 0111 | 0010 = 0111, which is 7.

Describe how the bitwise AND, OR, and XOR operators work with simple examples.

Think about comparing bits like switches being on or off.

Explain what happens when you use left shift (<<) and right shift (>>) operators on a number.

Imagine sliding beads on a string to the left or right.

Practice

1. Which bitwise operator in Rust returns 1 only if both bits are 1?
Example: 5 & 3

easy

A. AND (&)

B. OR (|)

C. XOR (^)

D. NOT (!)

Solution

1. Step 1: Understand the AND operator

   The AND operator (&) compares each bit of two numbers and returns 1 only if both bits are 1.

2. Step 2: Compare with other operators

   OR (|) returns 1 if either bit is 1, XOR (^) returns 1 if bits differ, NOT (!) flips bits.

3. Final Answer:

   AND (&) -> Option A

4. Quick Check:

   AND returns 1 only if both bits are 1 [OK]

Hint: AND is the only operator needing both bits as 1 [OK]

Common Mistakes:

• Confusing AND with OR which returns 1 if either bit is 1
• Thinking XOR returns 1 if both bits are 1
• Using NOT (!) as a binary operator instead of unary

2. Which of the following is the correct syntax for a bitwise XOR operation in Rust between variables a and b?

easy

A. a ! b

B. a & b

C. a | b

D. a ^ b

Solution

1. Step 1: Recall XOR operator symbol

   In Rust, the bitwise XOR operator is represented by the caret symbol (^).

2. Step 2: Check other operators

   & is AND, | is OR, and ! is unary NOT, so only a ^ b is correct for XOR.

3. Final Answer:

   a ^ b -> Option D

4. Quick Check:

   XOR uses ^ symbol in Rust [OK]

Hint: XOR uses ^ symbol, not & or | [OK]

Common Mistakes:

• Using & or | instead of ^ for XOR
• Trying to use ! as a binary operator
• Confusing syntax with other languages

3. What is the output of this Rust code?

let x = 0b1010;  // binary 10
let y = 0b1100;  // binary 12
let result = x | y;
println!("{:04b}", result);

medium

A. 1000

B. 1110

C. 0110

D. 1010

Solution

1. Step 1: Convert binary to bits and apply OR

   x = 1010, y = 1100. OR (|) returns 1 if either bit is 1. 1010 | 1100 = 1110

2. Step 2: Print result in 4-bit binary

   Result is 1110 in binary, which matches 1110.

3. Final Answer:

   1110 -> Option B

4. Quick Check:

   Bitwise OR of 1010 and 1100 = 1110 [OK]

Hint: OR sets bits where either input bit is 1 [OK]

Common Mistakes:

• Mixing up OR with AND results
• Reading binary digits incorrectly
• Forgetting to print in binary format

4. Identify the error in this Rust code snippet:

let a = 0b1010;
let b = 0b0101;
let c = a && b;
println!("{}", c);

medium

A. Incorrect binary literal syntax

B. Missing semicolon after let b

C. Using && instead of & for bitwise AND

D. println! macro missing format specifier

Solution

1. Step 1: Check operator usage

   The code uses && which is a logical AND, not bitwise AND. Bitwise AND uses &.

2. Step 2: Verify other syntax

   Semicolons are present, binary literals are correct, and println! has a format specifier, so no errors there.

3. Final Answer:

   Using && instead of & for bitwise AND -> Option C

4. Quick Check:

   Bitwise AND uses & not && [OK]

Hint: Use & for bitwise AND, && is logical AND [OK]

Common Mistakes:

• Confusing logical AND (&&) with bitwise AND (&)
• Assuming binary literals need prefix changes
• Missing format specifier in println! macro

5. Given a number n, which Rust expression flips (toggles) the 3rd bit (counting from 0) of n using bitwise operators?

hard

A. n ^ (1 << 3)

B. n & (1 << 3)

C. n | (1 << 3)

D. ~n & (1 << 3)

Solution

1. Step 1: Understand bit flipping with XOR

   XOR (^) with 1 flips the bit: if bit is 0 it becomes 1, if 1 it becomes 0. Shifting 1 by 3 sets the mask for the 3rd bit.

2. Step 2: Analyze other options

   & with mask clears bits except the 3rd bit, | sets the 3rd bit to 1, ~n & mask is unrelated to flipping a single bit.

3. Final Answer:

   n ^ (1 << 3) -> Option A

4. Quick Check:

   XOR with bit mask flips that bit [OK]

Hint: XOR with 1 at bit position flips that bit [OK]

Common Mistakes:

• Using & or | which clear or set bits instead of flipping
• Confusing ~ (NOT) usage
• Not shifting 1 to correct bit position