Ord

  • Ord type contains types, the values of which can be ordered.

  • Ord contain functions (>) - gt, (<) - lt, (>=) - gte, (<=) - lte, given any two values of a given Ord type, you can determine whether one be greater than the other.

  • Ord is almost identical to Setoid’s equals, the only difference is that, this time, we return a boolean to indicate whether this <= that, rather than this == that. Using only gt, lt, gte, lte and equals (because every Ord is a Setoid), we can derive all the things we might want:

Graphic

graph LR; A[Setoid] --> B(Ord)

Example

import { equals } from 'ramda'

// Greater than. The OPPOSITE of lte.
// gt :: Ord a => a -> a -> Boolean
const gt = (x, y) => {
  return !lte(x, y)
}

// Greater than or equal.
// gte :: Ord a => a -> a -> Boolean
const gte = (x, y) => {
  return gt(x, y) || equals(x)(y)
}

// Less than. The OPPOSITE of gt!
// lt :: Ord a => a -> a -> Boolean
const lt = (x, y) => {
  return !gte(x, y)
}

// Less than or equal. The OPPOSITE of gte!
// lte :: Ord a => a -> a -> Boolean
const lte = (x, y) => {
  return x <= y
}

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