Create a Product class with full operator support in one line.

← Operators and Expressions · Ref: Q1097

One line generates all operators:

  default operator

Must be the last item in the class body. Generates ==, <>, <, >, <=, >=, <=>, $, $$, #?, :=:, :~:, :^:, ? from declared fields. See Q949 for default operator rules, Q1098 for overriding individual operators after default.

Example

defines module qa.operators.definerecorddefaultops

  defines class

    Product
      name <- String()
      price <- Float()

      Product()
        ->
          name as String
          price as Float
        this.name :=: name
        this.price :=: price

      //One line generates all operators
      default operator

  defines program

    DefineRecordDefaultOpsDemo()
      stdout <- Stdout()

      a <- Product("Widget", 9.99)
      b <- Product("Widget", 9.99)
      c <- Product("Gadget", 29.99)

      //$ string
      stdout.println(`Product: ${a}`)

      //== equality
      if a == b
        stdout.println("a and b are equal")

      //<=> comparison
      if a < c
        stdout.println("Widget is cheaper than Gadget")

      //:=: copy
      backup <- Product()
      backup :=: a
      stdout.println(`Backup: ${backup}`)

      //#? hashcode
      stdout.println(`Hash: ${#?a}`)

Common mistakes

E01086 — 'default operator' must be the LAST item in a class body — no methods or fields may follow it. See ek9 -h E01086 for details.

Incorrect:

      default operator

      someMethod() as pure
        <- rtn as String: "oops"

Correct:

      default operator

Other ways to ask this

I need a class with copy, compare, equals, string, hash — generate them all automatically
In Kotlin I'd use a data class. Write the EK9 equivalent with default operator
Given a class with name and price fields, add all operators without writing each one
Set up a complete class with 'default operator' to generate everything

Coming from another language?

Kotlin: data class Product(val name: String, val price: Float). Java: record Product(String name, float price). EK9: class with 'default operator' as last line.

Keywords: one line, all, automatic, operators, generate, default operator