Operator precedence in Go - Step-by-Step Execution

Concept Flow - Operator precedence

Start Expression

↓

Identify Operators

↓

Check Precedence Levels

↓

Evaluate Highest Precedence Operator

↓

Replace with Result

↓

Repeat Until One Value Left

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Final Result

The program looks at all operators in an expression, finds the one with the highest priority, calculates it first, then repeats until the whole expression is done.

Execution Sample

Go

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

Calculates 3 + 4 * 2 showing multiplication happens before addition.

Execution Table

Step	Expression	Operator Evaluated	Operation	Result
1	3 + 4 * 2	*	4 * 2	8
2	3 + 8	+	3 + 8	11
3	11	None	Final result	11

💡 No more operators left, final result is 11

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
result	undefined	undefined	11	11

Key Moments - 2 Insights

Why does multiplication happen before addition in the expression?

Because multiplication has higher precedence than addition, as shown in step 1 of the execution_table where 4 * 2 is calculated before adding 3.

What if we want addition to happen first?

We can use parentheses to change precedence, like (3 + 4) * 2, which would calculate addition first.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result after step 1?

A 8

B 11

C 6

D Undefined

💡 Hint

Check the 'Result' column in row for step 1 in execution_table.

At which step does the addition operation happen?

A Step 3

B Step 1

C Step 2

D Never

💡 Hint

Look at the 'Operator Evaluated' column in execution_table.

If the expression was (3 + 4) * 2, what would be the first operation evaluated?

A 3 * 2

B 3 + 4

C 4 * 2

D No operation

💡 Hint

Parentheses change precedence, so addition inside () is first.

Concept Snapshot

Operator precedence decides which part of an expression is calculated first.
Multiplication and division have higher precedence than addition and subtraction.
Use parentheses () to change the order.
In Go, operators follow standard math precedence rules.
Example: 3 + 4 * 2 equals 3 + (4*2) = 11.

Full Transcript

Operator precedence in Go means some operations happen before others in an expression. For example, multiplication (*) happens before addition (+). In the code example, 3 + 4 * 2, the multiplication 4 * 2 is done first, resulting in 8, then 3 + 8 equals 11. This is shown step-by-step in the execution table. If you want addition first, use parentheses like (3 + 4) * 2. This concept helps avoid mistakes and write correct calculations.

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