Language Reference: Equality

Operators

The equals == operator can be used to check if two values are equal.

1 + 4 == 5

true

The not-equals != operator can be used to check if two values are not equal.

1 + 4 != 14

true

Definition

Equality in Pointless obeys the following rules:

• Values of different types are never equal.

  "0" == 0
  true == 1

  false
  false
  

• true, false, and none are equal to themselves.

  true == true
  false == false
  none == none

  true
  true
  true
  

• Numbers are equal if they have the same value.

  1e2 == 100.0
  42 == 7

  true
  false
  

• Strings are equal if they contain the same characters in the same order.

  "hello" == "hello"
  "Hello!" == "hello?"

  true
  false
  

• Lists are equal if they contain the same elements in the same order.

  ["a", "b", "c"] == ["a", "b", "c"]
  ["a", "b", "c"] == ["a", "c", "b"]

  true
  false
  

• Sets are equal if they contain the same values, regardless of order.

  Set.of([0, 1]) == Set.of([1, 0])
  Set.of([0, 1]) == Set.of([2, 1, 0])

  true
  false
  

• Objects are equal if they contain the same key-value pairs, regardless of order.

  { city: "Boston", state: "MA" } == { state: "MA", city: "Boston" }
  { county: "Suffolk", state: "MA" } == { city: "Boston", state: "MA" }

  true
  false
  

• Tables are equal if their row lists (lists whose elements are row objects) are equal. Equivalently, tables are equal if their column objects (objects whose keys are column names and whose values are lists of each column's values) are equal.

  t1 = Table.of([{ state: "CA", rank: 1 }, { state: "TX", rank: 2 }])
  t2 = Table.of({ state: ["CA", "TX"], rank: [1, 2] })
  t1 == t2
  
  t3 = Table.of({ state: ["CA", "TX"], rank: [1, 2] })
  t4 = Table.of({ state: ["TX", "CA"], ranking: [1, 2] })
  t3 == t4

  true
  false
  

• A function is equal to itself. Two functions which do different things are not equal. Two functions which do the same thing may or may not be equal.

  fn inc(n)
    n + 1
  end
  
  inc == inc
  
  inc == fn(n) n * 3 end
  
  fn(n) n * 3 end == fn(n) n * 3 end -- May or may not be equal

  true
  false
  false
  

• A ref is only ever equal to itself. Two different refs are not equal, even if they contain the same value.

  ref = Ref.of(0)
  ref == ref
  ref == Ref.of(0)

  true
  false
  

• Equality is defined recursively for data structures. Values inside these structures are compared using these same rules.