How to slice in golang

Golang is an efficient, strongly typed, concurrency-safe programming language that is increasingly favored by developers because of its excellent performance and ease of use. Slice is one of the important data structures in Golang. It is a dynamic array that can dynamically increase or decrease the length as needed. It is one of the commonly used data structures in Golang. This article will introduce in detail how to use Golang slicing.

1. Definition of slice

In Golang, use the make() function to create a slice. The make() function is used as follows:

slice1 := make( []T, len, cap)

Among them, T refers to the type of elements in the slice, len refers to the length of the slice, and cap refers to the capacity of the slice, that is, the length of the underlying array of the slice.

For example, define an int type slice with a length of 3 and a capacity of 5. The code is as follows:

slice1 := make([]int, 3, 5)

The above code will create a slice containing 3 integer elements, and the length of the underlying array is 5.

2. Slice operation

2.1 Slice traversal

In Golang, slice traversal can be implemented using the for loop and range keyword.

1. Using a for loop

When using a for loop to traverse a slice, you can use the len() function to get the length of the slice and use the index to access each element. For example, define an int type slice containing 1 to 5, the code is as follows:

slice1 := []int{1, 2, 3, 4, 5}
for i := 0; i < ; len(slice1); i {

fmt.Println(slice1[i])

}

The above code will output each element in slice slice1.

2. Use the range keyword

Use the range keyword to traverse slices more concisely. For example, for the above slice slice1, you can use the following code to traverse:

slice1 := []int{1, 2, 3, 4, 5}
for index, item := range slice1 {

fmt.Printf("Index: %d, Value: %d

", index, item)
}

This code will output the index and value of each element in the slice.

2.2 Appending the slice

Slices can dynamically store data, and you can use the append() function to append elements to the slice.

For example, define an int type slice containing 1 to 3, and the code is as follows:

slice1 := []int{1, 2, 3}

Now, we want to append two elements 4 and 5 to the slice. We can use the append() function to achieve this, for example:

slice1 = append(slice1, 4, 5)

It should be noted that when appending elements to a slice, if the capacity of the underlying array is insufficient, a larger underlying array will be reallocated and the original The elements are copied to the new underlying array, so you need to pay attention to the expansion of the slice. Generally speaking, in order to avoid frequent expansion, you can preset the length of the underlying array of the slice.

2.3 Interception of slices

In addition to appending elements, you can also intercept the slice to turn it into a new slice. The interception operation of the slice uses the slice operator [x:y], where x is the starting position of the interception (Counting starts from 0), y is the end position of interception.

For example, define an int type slice containing 1 to 5, the code is as follows:

slice1 := []int{1 , 2, 3, 4, 5}

To intercept the first 3 elements in the slice, you can use the following code:

slice2 := slice1[0:3]

The above code will return a slice slice2 containing the first three elements in slice slice1.

2.4 Copy of slice

Use the copy() function in Golang to copy a slice to In another slice, the example is as follows:

slice1 := []int{1, 2, 3}
slice2 := make([]int, len(slice1))
copy(slice2 , slice1)
fmt.Println(slice2)

The above code will create a slice slice2 with the same length as slice1, and copy the elements from slice1 to slice2.

3. Slicing expansion problem

When appending elements, the capacity of the underlying array of the slice may be insufficient, and expansion operations will occur at this time. Slicing expansion requires reallocating memory and copying the original elements to the new underlying array, which is a time-consuming process. Therefore, when designing slices, the capacity of the slice needs to be considered.

In Golang, you can use the cap() function to get the capacity of the slice. If the capacity of the slice is full, memory needs to be reallocated to double the length of the underlying array.

For example, define an int type slice with a length of 2 and a capacity of 3. The code is as follows:

slice1 := make([]int, 2, 3)

Now, we want to append 3 elements to the slice, which can be achieved in the following way:

for i := 3; i

slice1 = append(slice1, i)
fmt.Println("Len:", len(slice1), ", Cap:", cap(slice1))

}

The above code will output the length and capacity of the slice after each appended element.

It should be noted that the expansion operation may cause the underlying array address of the slice to change, so it is necessary to avoid using a pointer to the original slice as a parameter of a function, which may cause potential problems.

4. Tips for using slices

When designing Golang programs, slicing is a very commonly used data structure. Here are some usage tips:

• When using slices in a loop, you can first assign a value to the slice outside the loop. This can avoid reallocating memory for the slice in each iteration and reduce memory overhead.
• When a slice is used as a function parameter, it can be declared as a pointer type. This can avoid copying the entire slice when the function is called and reduce memory consumption.
• In Golang, slices can use the append() function to append elements to them, but if you need to delete elements, you need to use the copy and intercept operations of the slice.

5. Summary

Slicing in Golang is a very commonly used data structure that can dynamically store elements and automatically expand. When using slices, you need to pay attention to the capacity of the underlying array to avoid frequent expansion operations.

This article introduces the definition, operation and usage skills of slices. I hope it can be helpful to Golang developers.

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