M - the MonadRec instanceA - the carrier typepublic final class SafeT<M extends MonadRec<?,M>,A> extends Object implements MonadT<M,A,SafeT<M,?>,SafeT<?,?>>
monad transformer that can safely interpret deeply nested left- or right-associated
binds for any MonadRec.
Example:
Times.<Fn1<Integer, Integer>>times(100_000, f -> f.fmap(x -> x + 1), id()).apply(0); // stack-overflow
Times.<SafeT<Fn1<Integer, ?>, Integer>>times(100_000, f -> f.fmap(x -> x + 1), safeT(id()))
.<Fn1<Integer, Integer>>runSafeT()
.apply(0); // 100_000
Inspired by Phil Freeman's paper Stack Safety for Free.
| Modifier and Type | Method and Description |
|---|---|
<B> SafeT<M,B> |
discardL(Applicative<B,SafeT<M,?>> appB)
Sequence both this
Applicative and appB, discarding this Applicative's
result and returning appB. |
<B> SafeT<M,A> |
discardR(Applicative<B,SafeT<M,?>> appB)
Sequence both this
Applicative and appB, discarding appB's result and
returning this Applicative. |
<B> SafeT<M,B> |
flatMap(Fn1<? super A,? extends Monad<B,SafeT<M,?>>> f)
Chain dependent computations that may continue or short-circuit based on previous results.
|
<B> SafeT<M,B> |
fmap(Fn1<? super A,? extends B> fn)
Covariantly transmute this functor's parameter using the given mapping function.
|
<B> Lazy<SafeT<M,B>> |
lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,SafeT<M,?>>> lazyAppFn)
Given a
lazy instance of this applicative over a mapping function, "zip" the two instances together
using whatever application semantics the current applicative supports. |
<B,N extends MonadRec<?,N>> |
lift(MonadRec<B,N> nb)
|
static Lift<SafeT<?,?>> |
liftSafeT()
|
<B> SafeT<M,B> |
pure(B b)
Lift the value
b into this applicative functor. |
static <M extends MonadRec<?,M>> |
pureSafeT(Pure<M> pureM)
|
<MA extends MonadRec<A,M>> |
runSafeT()
Recover the full structure of the embedded
Monad in a stack-safe way. |
static <M extends MonadRec<?,M>,A> |
safeT(MonadRec<A,M> ma)
|
<B> SafeT<M,B> |
trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,SafeT<M,?>>> bounce)
Given some operation yielding a
RecursiveResult inside this MonadRec, internally trampoline the
operation until it yields a termination instruction. |
<B> SafeT<M,B> |
zip(Applicative<Fn1<? super A,? extends B>,SafeT<M,?>> appFn)
Given another instance of this applicative over a mapping function, "zip" the two instances together using
whatever application semantics the current applicative supports.
|
public <MA extends MonadRec<A,M>> MA runSafeT()
Monad in a stack-safe way.MA - the witnessed target typeMonadpublic <B> SafeT<M,B> fmap(Fn1<? super A,? extends B> fn)
fmap in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>fmap in interface Functor<A,SafeT<M extends MonadRec<?,M>,?>>fmap in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>fmap in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>fmap in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the new parameter typefn - the mapping functionpublic <B,N extends MonadRec<?,N>> SafeT<N,B> lift(MonadRec<B,N> nb)
lift in interface MonadBase<M extends MonadRec<?,M>,A,SafeT<?,?>>lift in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the MonadRec carrier typeN - the argument MonadRec witnessnb - the argument MonadRecMonadBasepublic <B> SafeT<M,B> flatMap(Fn1<? super A,? extends Monad<B,SafeT<M,?>>> f)
flatMap in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>flatMap in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>flatMap in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the resulting monad parameter typef - the dependent computation over Apublic <B> SafeT<M,B> zip(Applicative<Fn1<? super A,? extends B>,SafeT<M,?>> appFn)
zip in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>zip in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>zip in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>zip in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the resulting applicative parameter typeappFn - the other applicative instancepublic <B> Lazy<SafeT<M,B>> lazyZip(Lazy<? extends Applicative<Fn1<? super A,? extends B>,SafeT<M,?>>> lazyAppFn)
lazy instance of this applicative over a mapping function, "zip" the two instances together
using whatever application semantics the current applicative supports. This is useful for applicatives that
support lazy evaluation and early termination.lazyZip in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>lazyZip in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>lazyZip in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>lazyZip in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the resulting applicative parameter typelazyAppFn - the lazy other applicative instanceMaybe,
Eitherpublic <B> SafeT<M,B> discardL(Applicative<B,SafeT<M,?>> appB)
Applicative and appB, discarding this Applicative's
result and returning appB. This is generally useful for sequentially performing side-effects.discardL in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>discardL in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>discardL in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>discardL in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the type of the returned Applicative's parameterappB - the other Applicativepublic <B> SafeT<M,A> discardR(Applicative<B,SafeT<M,?>> appB)
Applicative and appB, discarding appB's result and
returning this Applicative. This is generally useful for sequentially performing side-effects.discardR in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>discardR in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>discardR in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>discardR in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the type of appB's parameterappB - the other Applicativepublic <B> SafeT<M,B> pure(B b)
b into this applicative functor.pure in interface Applicative<A,SafeT<M extends MonadRec<?,M>,?>>pure in interface Monad<A,SafeT<M extends MonadRec<?,M>,?>>pure in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>pure in interface MonadT<M extends MonadRec<?,M>,A,SafeT<M extends MonadRec<?,M>,?>,SafeT<?,?>>B - the type of the returned applicative's parameterb - the valuepublic <B> SafeT<M,B> trampolineM(Fn1<? super A,? extends MonadRec<RecursiveResult<A,B>,SafeT<M,?>>> bounce)
RecursiveResult inside this MonadRec, internally trampoline the
operation until it yields a termination instruction.
Stack-safety depends on implementations guaranteeing that the growth of the call stack is a constant factor independent of the number of invocations of the operation. For various examples of how this can be achieved in stereotypical circumstances, see the referenced types.
trampolineM in interface MonadRec<A,SafeT<M extends MonadRec<?,M>,?>>B - the ultimate resulting carrier typebounce - the function to internally trampolineMonadRecfor a basic implementation,
for a {@link CoProduct2 coproduct} implementation,
for an implementation leveraging an already stack-safe {@link Monad#flatMap(Fn1)},
for a {@link MonadT monad transformer} implementation