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Exploring the New cmp Package in Go v1.21: Simplifying Ordered Value Comparisons

Yash Goel 40


With the release of Go v1.21, a new addition to the standard library has caught the attention of the programming community — the cmp package. This package introduces a set of types and functions specifically designed for comparing ordered values in a consistent and efficient manner. In this article, we'll delve into the functionalities and features of the cmp package, highlighting its benefits and showcasing how it simplifies value comparisons.

Understanding the cmp Package

The cmp package is all about comparing ordered values – those that can be logically ordered using operators like <, <=, >, and >=. The package provides a set of functions and a constraint type, Ordered, to facilitate these comparisons.

Functions in the cmp Package

Compare function

The Compare function is the cornerstone of the cmp package. It allows us to compare two ordered values and returns an integer indicating their relationship:

  • -1: x is less than y
  • 0: x equals y
  • 1: x is greater than y

For example:

import (

func main() {
x, y := 5, 7
result := cmp.Compare(x, y)
fmt.Println(result) // Output: -1

Less function

The Less function determines whether one value is less than another. It returns a boolean value, true if x is less than y, and false otherwise. This function is particularly useful when you only need to compare values without requiring their exact relationship.

import (

func main() {
x, y := 10.5, 8.2
result := cmp.Less(x, y)
fmt.Println(result) // Output: false

The Ordered Constraint

The Ordered interface is a constraint that encompasses any ordered type. This includes integer types, floating-point types, and strings. The constraint is designed to encompass future ordered types as well, making the cmp package adaptable to potential additions in upcoming Go releases.

type Ordered interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
~float32 | ~float64 |

Handling Floating-Point Values and NaN

One of the challenges with comparing floating-point values is dealing with special cases like NaN (not-a-number) and negative zero. The cmp package addresses these challenges. For example, NaN is considered less than any non-NaN value, and negative zero is treated as equal to positive zero.


The introduction of the cmp package in Go v1.21 is a significant step towards simplifying and standardizing value comparisons for ordered types. By providing functions like Compare and Less, along with the Ordered constraint, Go developers now have a reliable and efficient way to handle ordered value comparisons across various data types. This package not only enhances code readability but also reduces the complexity of handling special cases, making it easier to write clean and maintainable Go code.