[MLton] Is there any "Unsafe.cast" in mlton?

[cuisa@cs.bu.edu]

Hi,

I am using Mlton to compile ML code for experiments. I need a function like 
Unsafe.cast in SML/NJ. Is there such a function in Mlton? I found from 
mlton.org that the Unsafe structure in Mlton is a subset of that in SML/NJ. 
Does it mean there is no cast function in Mlton? If so, is there any solution 
to achieve the same functionality as Unsafe.cast?

Thanks,

Sa Cui