I try to create a monad:
datatype result a x =
Ok of a
| Err of x
fun mreturn [a] [x] (r : a) : result a x = Ok r
fun mbind [a] [b] [x] (r : result a x) (f : a -> result b x) : result b x =
case r of
Ok r => f r
| Err x => Err x
val result_monad = mkMonad
{
Return = @@mreturn,
Bind = @@mbind
}
I think the error message tries to tell me that x is not defined enough. Is
there a way to fix this? When I remove x from result, it compiles.
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