Operator precedence in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is operator precedence in Go?

Operator precedence determines the order in which operators are evaluated in an expression. Operators with higher precedence are evaluated before those with lower precedence.

beginner

Which operator has higher precedence: multiplication (*) or addition (+)?

Multiplication (*) has higher precedence than addition (+), so it is evaluated first in an expression.

beginner

How does Go evaluate the expression: 3 + 4 * 2?

Go first multiplies 4 * 2 = 8, then adds 3 + 8 = 11, because * has higher precedence than +.

beginner

What role do parentheses play in operator precedence?

Parentheses override normal precedence rules by forcing the expression inside them to be evaluated first.

intermediate

List the precedence order of these Go operators from highest to lowest: *, +, ==, &&.

The order is: * (multiplication), + (addition), == (equality), && (logical AND). Operators higher in the list are evaluated first.

In Go, which operator is evaluated first in the expression: 5 + 3 * 2?

A Addition (+)

B Depends on variable types

C Both at the same time

D Multiplication (*)

Multiplication (*) has higher precedence than addition (+), so 3 * 2 is evaluated first.

What does parentheses do in the expression: (5 + 3) * 2?

A They have no effect

B They make addition happen before multiplication

C They make multiplication happen before addition

D They change the operators

Parentheses force the addition 5 + 3 to be evaluated before multiplication.

Which operator has the lowest precedence in Go?

A && (logical AND)

B * (multiplication)

C + (addition)

D == (equality)

Logical AND (&&) has lower precedence than arithmetic and comparison operators.

In Go, what is the result of 10 / 2 * 3?

A 30

B 5

C 15

D 1.5

Division and multiplication have the same precedence and are evaluated left to right: (10 / 2) * 3 = 5 * 3 = 15.

Which operator is evaluated first in: true && false == false?

A == (equality)

B && (logical AND)

C Both at the same time

D Depends on the compiler

Equality (==) has higher precedence than logical AND (&&), so false == false is evaluated first.

Explain how operator precedence affects the evaluation of arithmetic expressions in Go.

Think about which operations happen first in expressions like 3 + 4 * 2.

Describe the precedence order of arithmetic, comparison, and logical operators in Go.

Consider operators like *, +, ==, and &&.

Practice

1. In Go, which operator has the highest precedence among these: +, -, *, /?

easy

A. Subtraction (-)

B. Addition (+)

C. All have the same precedence

D. Multiplication (*) and division (/)

Solution

1. Step 1: Recall operator precedence rules in Go

   Multiplication (*) and division (/) have higher precedence than addition (+) and subtraction (-).

2. Step 2: Compare given operators

   Among the given operators, * and / are evaluated before + and -.

3. Final Answer:

   Multiplication (*) and division (/) -> Option D

4. Quick Check:

   *, / > +, - [OK]

Hint: Remember: multiply/divide before add/subtract [OK]

Common Mistakes:

• Thinking all operators have equal precedence
• Confusing addition with multiplication precedence
• Ignoring division operator precedence

2. Which of the following Go expressions is syntactically correct and respects operator precedence?

easy

A. result := 5 + (3 * 2

B. result := 5 + * 3 2

C. result := 5 + 3 * 2

D. result := 5 + 3 * * 2

Solution

1. Step 1: Check each expression for syntax correctness

   result := 5 + 3 * 2 uses valid operators and correct syntax. Options B, C, and D have syntax errors like misplaced operators or missing parentheses.

2. Step 2: Confirm operator precedence in result := 5 + 3 * 2

   Multiplication (*) happens before addition (+), so expression is valid and respects precedence.

3. Final Answer:

   result := 5 + 3 * 2 -> Option C

4. Quick Check:

   Valid syntax and precedence in result := 5 + 3 * 2 [OK]

Hint: Check for misplaced or missing operators and parentheses [OK]

Common Mistakes:

• Using two operators in a row without operand
• Missing closing parentheses
• Confusing operator placement

3. What is the output of this Go code?

package main
import "fmt"
func main() {
    x := 2 + 3 * 4 - 6 / 2
    fmt.Println(x)
}

medium

A. 11

B. 10

C. 12

D. 14

Solution

1. Step 1: Apply operator precedence to expression

   Multiplication and division first: 3 * 4 = 12, 6 / 2 = 3.

2. Step 2: Calculate addition and subtraction left to right

   Expression becomes 2 + 12 - 3 = 14 - 3 = 11.

3. Final Answer:

   11 -> Option A

4. Quick Check:

   2 + (3*4) - (6/2) = 11 [OK]

Hint: Do * and / before + and -, then left to right [OK]

Common Mistakes:

• Adding before multiplying
• Subtracting before division
• Ignoring left-to-right evaluation for + and -

4. Identify the error in this Go code snippet related to operator precedence:

package main
import "fmt"
func main() {
    result := 10 / 2 * 3
    + 4 - 1
    fmt.Println(result)
}

medium

A. Line break splits expression incorrectly without continuation

B. Division operator has lower precedence than multiplication

C. Missing parentheses around addition and subtraction

D. Using + and - operators together causes syntax error

Solution

1. Step 1: Check expression syntax across lines

   The expression is split across two lines without proper continuation, causing a syntax error.

2. Step 2: Understand Go line continuation rules

   Go requires expressions split across lines to be clearly continued, usually by operators at line end or parentheses.

3. Final Answer:

   Line break splits expression incorrectly without continuation -> Option A

4. Quick Check:

   Line breaks need proper continuation [OK]

Hint: Avoid breaking expressions without operators or parentheses [OK]

Common Mistakes:

• Assuming operator precedence causes error
• Thinking + and - together cause syntax error
• Ignoring Go's line continuation rules

5. Given the Go expression:

result := 8 + 2 * (5 - 3) / 2 - 1

What is the correct value of result after evaluation?

hard

A. 8

B. 9

C. 10

D. 11

Solution

1. Step 1: Evaluate parentheses first

   (5 - 3) = 2.

2. Step 2: Apply multiplication and division left to right

   2 * 2 = 4, then 4 / 2 = 2.

3. Step 3: Perform addition and subtraction left to right

   8 + 2 = 10, then 10 - 1 = 9.

4. Final Answer:

   9 -> Option B

5. Quick Check:

   8 + 2*(2)/2 - 1 = 9 [OK]

Hint: Calculate parentheses first, then * /, then + - left to right [OK]

Common Mistakes:

• Ignoring parentheses priority
• Doing addition before multiplication
• Dividing before multiplying inside parentheses