Why Can't Go Generics Use `comparable` with Order Operators (``, etc.)?

Why can't you use comparable constraint with order operators in Go generics?

While exploring Go generics, you may encounter an error when using the > operator on built-in comparable types. This is because the comparable constraint only supports equality operators (== and !=), while order operators (<, >, <=, and >=) require the Ordered constraint.

What is the difference between comparable and ordered types?

The comparable constraint is for types that support equality operators, including arrays and structs with comparable fields. However, the order operators are applicable to types that are ordered, such as numeric types and strings.

Solution for Go 1.18 to 1.20

In Go versions 1.18 to 1.20, you can use the constraints.Ordered constraint to support order operators. This constraint includes types like Integer, Float, and ~string.

Solution for Go 1.21 and above

In Go 1.21, the standard library introduces the cmp package with the Ordered constraint and two generic functions, Less and Compare, which facilitate working with ordered types.

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