primop TryTakeMVarOp "tryTakeMVar#" GenPrimOp
MVar# s a -> State# s -> (# State# s, Int#, a #)
{If {\tt MVar\#} is empty, immediately return with integer 0 and value undefined.
Otherwise, return with integer 1 and contents of {\tt MVar\#}, and set {\tt MVar\#} empty.}
with
primop TryTakeMVarOp "tryTakeMVar#" GenPrimOp
MVar# s a -> State# s -> (# State# s, Int#, a #)
{If {\tt MVar\#} is empty, immediately return with integer 0 and value undefined.
Otherwise, return with integer 1 and contents of {\tt MVar\#}, and set {\tt MVar\#} empty.}
with