Expecting one more argument to ‘RedeemerType’

Question

My code is here

marketConstraints :: Market -> TxConstraints (RedeemerType -> ScriptContext -> Bool) (DatumType, ())
marketConstraints market = mustValidateIn (to $ scriptAddress market)

I am not sure how to do to correct this errors.

src/MarketState.hs:58:87: error:
   • Expecting one more argument to ‘RedeemerType’
      Expected a type, but ‘RedeemerType’ has kind ‘* -> *’
    • In the first argument of ‘TxConstraints’, namely
        ‘(RedeemerType -> ScriptContext -> Bool)’
      In the type signature:
        marketConstraints :: Market
                             -> TxConstraints (RedeemerType
                                               -> ScriptContext -> Bool) (DatumType, ())
   |
58 | marketConstraints :: Market -> TxConstraints (RedeemerType -> ScriptContext -> Bool) (DatumType, ())
   |                                               ^^^^^^^^^^^^

src/MarketState.hs:58:87: error:
    • Expecting one more argument to ‘DatumType’
      Expected a type, but ‘DatumType’ has kind ‘* -> *’
    • In the second argument of ‘TxConstraints’, namely
        ‘(DatumType, ())’
      In the type signature:
        marketConstraints :: Market
                             -> TxConstraints (RedeemerType
                                               -> ScriptContext -> Bool) (DatumType, ())

Answer 1

This is entirely related to Haskell. The kind of (->) is * -> * -> * thus in your type signature, both left-hand & right-hand side of -> must have kind * but some of your parameters such as RedeemerType & DatumType are higher kinded. If you are new to all this "kind" jargon, I would suggest this blog post on it.