Best practices for remainder operations in go language

Best practice: Use the built-in function math.Mod() to consider negative numbers to avoid floating-point remainder rounding errors (math.Remainder()) and use bitwise operations to improve performance (only if the divisor is a power of 2) Practical application: mod Operations (computing remainders) Loop controls (printing specific elements) Data structures (hash tables and key maps in sets)

Go language remainder operations best practices

Introduction

In the Go language, the operator for finding the remainder is %. When used, it divides the left operand by the right operand and returns the remainder as the result. Remainder operations are widely used in different scenarios, including modular operations, loop control and data structures.

Best Practice

1. Use the built-in remainder function

For simple remainder calculations, it is recommended to use the built-in The math.Mod function. Like the % operator, it divides the left operand by the right operand and returns the remainder, but it avoids some overflow and rounding behaviors that can lead to unexpected results.

import "math"

result := math.Mod(10, 3) // result 等于 1

2. Consider negative numbers

When calculating the remainder of a negative number, the % operator may not produce the expected results. For example, the result of -10 % 3 is -1 instead of 2 because the modulo operation in Go always produces a result with the same sign as the divisor. To get the correct remainder, convert the left operand to a non-negative number and then perform the modulo operation.

dividend := -10
result := dividend % 3
if result < 0 {
    result += 3
}
// result 等于 2

3. Avoid rounding errors

For the remainder of floating point numbers, the % operator may cause rounding errors. This is because floating point numbers are represented in computers as binary, so their division operations may not be exact. To avoid this problem, you can use the math.Remainder function to calculate the remainder of a floating point number. This function is guaranteed to return a remainder with the same sign as the left operand.

dividend := 10.5
divisor := 3.0
result := math.Remainder(dividend, divisor) // result 等于 1.5

4. Using bitwise operations

In some cases, especially when smaller integers are involved, using bitwise operations for modulo operations can improve performance. For divisors where n is a power of 2, you can use the following formula to calculate the remainder:

remainder := number & (divisor - 1) // 当 divisor 是 2 的幂时

Practical case

Modular operation

Modulo arithmetic is a classic application of remainder arithmetic. It is used to calculate the remainder of a given number divided by another number. For example, the following code calculates the remainder when 25 is divided by 7:

remainder := 25 % 7 // remainder 等于 4

Loop control

The remainder operation can also be used in loop control. For example, the following code prints odd numbers from 1 to 10:

for i := 1; i <= 10; i++ {
    if i % 2 == 1 {
        fmt.Println(i)
    }
}

Data Structure

In data structures such as hash tables and sets, the remainder operation is used to convert keys Map to a specific location in a bucket or collection. For example, the following code looks up a key in a hash table:

hashValue := key % tableSize // 计算哈希值
entry := table[hashValue] // 从哈希表中获取对应的条目

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