21 replies

The Importance of Hash Implementation for Equal in TypeScript

why does

Equal

Equal

require a

Hash

Hash

implementation?

if (isEqual(self) && isEqual(that)) {
  return Hash.hash(self) === Hash.hash(that) && self[symbol](that)
}

if (isEqual(self) && isEqual(that)) {
  return Hash.hash(self) === Hash.hash(that) && self[symbol](that)
}

why is just

self[symbol](that)

self[symbol](that)

not enough?
I understand that if that type implements

Hash

Hash

, the hashes should be the same if the objects are equal
But I could see a situation where you want to implement

Equal

Equal

for a type, but it is not necessary to implement

Hash

Hash