Safe Haskell | None |
---|---|
Language | Haskell2010 |
Effect
Interpretations
runFixpoint :: (forall x. Sem r x -> x) -> Sem (Fixpoint ': r) a -> Sem r a Source #
Run a Fixpoint
effect purely.
Note: This is subject to the same traps as MonadFix
instances for
monads with failure: this will throw an exception if you try to recursively use
the result of a failed computation in an action whose effect may be observed
even though the computation failed.
For example, the following program will throw an exception upon evaluating the
final state:
bad :: (Int, Either () Int)
bad =
Int 1
. run
. runFixpoint
run
. runLazyState
runError
$ mdo
put
a
a <- throw
()
return a
@
runFixpoint
also operates under the assumption that any effectful
state which can't be inspected using Inspector
can't contain any
values. This is true for all interpreters featured in this package,
and is presumably always true for any properly implemented interpreter.
runFixpoint
may throw an exception if it is used together with an
interpreter that uses weave
improperly.
If runFixpoint
throws an exception for you, and it can't
be due to any of the above, then open an issue over at the
GitHub repository for polysemy.
runFixpointM :: (MonadFix m, Member (Embed m) r) => (forall x. Sem r x -> m x) -> Sem (Fixpoint ': r) a -> Sem r a Source #
Run a Fixpoint
effect in terms of an underlying MonadFix
instance.
Note: runFixpointM
is subject to the same caveats as runFixpoint
.