How to Compare Functions in Go?

How to Compare Functions in Go

Introduction

In Go, functions can be referenced by variables and passed as arguments to other functions. However, it is important to note that functions in Go are not directly comparable. This means that you cannot use the standard comparison operators (==, !=, etc.) to determine if two functions are equal.

Correct Comparison Method

The only way to accurately compare two functions is to compare their addresses. This is because the address of a function uniquely identifies it. To obtain the address of a function, you can use either:

• fmt.Sprintf(): This method prints the function address to a string and stores it in a variable.
• reflect.Value.Pointer(): This method returns the raw address of a function value.

Example

Consider the following Go code:

<code class="go">type Action func(foo string)

var Undefined Action = func(foo string) {}
var Defined Action = func(foo string) {}

func compareFunctions() {
    if fmt.Sprintf("%v", Undefined) == fmt.Sprintf("%v", Undefined) {
        fmt.Println("Undefined and Undefined are equal")
    } else {
        fmt.Println("Undefined and Undefined are not equal")
    }

    if fmt.Sprintf("%v", Defined) == fmt.Sprintf("%v", Defined) {
        fmt.Println("Defined and Defined are equal")
    } else {
        fmt.Println("Defined and Defined are not equal")
    }

    if fmt.Sprintf("%v", Undefined) == fmt.Sprintf("%v", Defined) {
        fmt.Println("Undefined and Defined are equal")
    } else {
        fmt.Println("Undefined and Defined are not equal")
    }
}</code>

When you run this code, it produces the following output:

Undefined and Undefined are equal
Defined and Defined are equal
Undefined and Defined are not equal

This output demonstrates that functions can be compared using their addresses and that two functions with different addresses are not equal.

Conclusion

While function values in Go cannot be directly compared, it is possible to compare their addresses to determine if they are the same function. Using the methods described above, you can accurately identify whether two functions are equal in Go.

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