pokeElemOff

Write a value to a memory area regarded as an array of values of the same kind. The following equality holds:
pokeElemOff addr idx x =
poke (addr `plusPtr` (idx * sizeOf x)) x
Write a value to a memory area regarded as an array of values of the same kind. The following equality holds:
pokeElemOff addr idx x = 
poke (addr `plusPtr` (idx * sizeOf x)) x