Hi, As part of some work I'm doing I need to classify all PrimTyCons by the size of their representation as fields*. I need to classify them into two classes: pointer-sized (or smaller) and larger-than-pointer-sized. I've managed to figure out a bunch of them myself: Pointer-sized: addrPrimTyCon arrayPrimTyCon byteArrayPrimTyCon -- Represented as a pointer to heap object arrayArrayPrimTyCon -- Represented as a pointer to heap object charPrimTyCon doublePrimTyCon -- Only on 64-bit floatPrimTyCon intPrimTyCon int32PrimTyCon int64PrimTyCon -- Only on 64-bit mutableArrayPrimTyCon -- Represented as a pointer to heap object mutableByteArrayPrimTyCon -- Represented as a pointer to heap object mutableArrayArrayPrimTyCon -- Represented as a pointer to heap object wordPrimTyCon word32PrimTyCon word64PrimTyCon -- Only on 64-bit These ones I need help with: bcoPrimTyCon weakPrimTyCon mVarPrimTyCon tVarPrimTyCon mutVarPrimTyCon realWorldTyCon stablePtrPrimTyCon stableNamePrimTyCon statePrimTyCon threadIdPrimTyCon anyTyCon eqPrimTyCon liftedTypeKindTyCon unliftedTypeKindTyCon openTypeKindTyCon constraintKindTyCon superKindTyCon anyKindTyCon I would appreciate any help classifying the bottom half. I will use this to implement -funbox-strict-primitive-fields * For example: while the StgArrWords heap object is a multi-byte object its representation as a field e.g. in data T = C ByteArray# is one pointer (to the StgArrWords heap object). -- Johan