Symbols.purs

-- This is similar to StringEscapes except we are performing the same tests
-- with Symbols (at the type level).

module Symbols where

import Prelude
import Effect.Console (log)
import Prim.Symbol (class Append)
import Type.Data.Symbol (reflectSymbol)
import Type.Data.Symbol (append) as Symbol
import Test.Assert (assert')
import Type.Proxy (Proxy(..))

highS :: Proxy "\xd834"
highS = Proxy

lowS :: Proxy "\xdf06"
lowS = Proxy

loneSurrogates :: Boolean
loneSurrogates = reflectSymbol (Symbol.append highS lowS) == "\x1d306"

outOfOrderSurrogates :: Boolean
outOfOrderSurrogates = reflectSymbol (Symbol.append lowS highS) == "\xdf06\xd834"

notReplacing :: Boolean
notReplacing = reflectSymbol lowS /= "\xfffd"

main = do
  assert' "lone surrogates may be combined into a surrogate pair" loneSurrogates
  assert' "lone surrogates may be combined out of order to remain lone surrogates" outOfOrderSurrogates
  assert' "lone surrogates are not replaced with the Unicode replacement character U+FFFD" notReplacing
  log "Done"