What is the situation when golang cannot compare?

In computer programming, comparison operations are a very basic operation. In most programming languages, comparison operations are usually expressed using symbols such as "==" and "!=". However, in Go, comparisons do not always yield correct results. This is because in Go language, comparison operators can only be used on comparable types, not arbitrary values.

Go language is a very powerful programming language that can be used to develop various types of applications, including web applications, desktop applications, mobile applications, etc. The Go language is designed to make it easier to write efficient and maintainable programs. However, due to the strict restrictions on types in the Go language, some types cannot be compared.

In the Go language, only built-in types and structure types can perform comparison operations. Built-in types include int, float, bool, string and other types, while structure types are composite types composed of multiple fields. Therefore, if you want to compare values ​​of two custom types, you must first define a comparison function for that type. Otherwise, the compiler would not be able to tell whether the two values ​​are equal because they are represented differently in memory.

For example, the following code snippet will go wrong:

type Person struct {
    Name string
    Age  int
}

func main() {
    p1 := Person{"Bob", 30}
    p2 := Person{"Alice", 25}
    if p1 == p2 {
        fmt.Println("same person")
    } else {
        fmt.Println("different person")
    }
}

This code snippet defines a Person structure type and attempts to compare the values ​​of two Person types. However, since the Person type does not define a comparison function, the compiler will not be able to perform the comparison operation and will report an error:

invalid operation: p1 == p2 (struct containing []interface {} cannot be compared)

The way to solve this problem is to define a comparison function, such as:

func (p1 Person) Equal(p2 Person) bool {
    return p1.Name == p2.Name && p1.Age == p2.Age
}

This The function will compare two values ​​of type Person and return a Boolean value indicating whether they are equal. Then, you can use this function when comparing two Person type values, for example:

if p1.Equal(p2) {
    fmt.Println("same person")
} else {
    fmt.Println("different person")
}

This code snippet will output "different person" because p1 and p2 represent different Person type values.

Someone may ask, why does Go language have such restrictions on comparison operations? In fact, this is a choice made by Go language designers. They believe that strict restrictions on types can improve the stability and readability of programs. If you allow arbitrary types of values ​​to be compared, your code will be more complex and you may have problems that are not easy to debug.

In short, although comparison operators are not omnipotent in Go language, this does not mean that Go language cannot perform comparison operations. On the contrary, by defining appropriate comparison functions, we can easily compare values ​​of various user-defined types, thereby writing more stable, readable, and easy-to-maintain programs.

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