Class Choice2<A,B>
- java.lang.Object
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- com.jnape.palatable.lambda.adt.choice.Choice2<A,B>
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- Type Parameters:
A
- the first possible typeB
- the second possible type
- All Implemented Interfaces:
CoProduct2<A,B,Choice2<A,B>>
,Applicative<B,Choice2<A,?>>
,Bifunctor<A,B,Choice2<?,?>>
,BoundedBifunctor<A,B,java.lang.Object,java.lang.Object,Choice2<?,?>>
,Functor<B,Choice2<A,?>>
,Monad<B,Choice2<A,?>>
,MonadRec<B,Choice2<A,?>>
,Traversable<B,Choice2<A,?>>
- Direct Known Subclasses:
Choice2._A
,Choice2._B
public abstract class Choice2<A,B> extends java.lang.Object implements CoProduct2<A,B,Choice2<A,B>>, MonadRec<B,Choice2<A,?>>, Bifunctor<A,B,Choice2<?,?>>, Traversable<B,Choice2<A,?>>
Canonical ADT representation ofCoProduct2
. UnlikeEither
, there is no concept of "success" or "failure", so the domain of reasonable function semantics is more limited.
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Nested Class Summary
Nested Classes Modifier and Type Class Description private static class
Choice2._A<A,B>
private static class
Choice2._B<A,B>
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Constructor Summary
Constructors Modifier Constructor Description private
Choice2()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static <A,B>
Choice2<A,B>a(A a)
Static factory method for wrapping a value of typeA
in aChoice2
.static <A,B>
Choice2<A,B>b(B b)
Static factory method for wrapping a value of typeB
in aChoice2
.<C,D>
Choice2<C,D>biMap(Fn1<? super A,? extends C> lFn, Fn1<? super B,? extends D> rFn)
Dually map covariantly over both the left and right parameters.<C> Choice2<C,B>
biMapL(Fn1<? super A,? extends C> fn)
Covariantly map over the left parameter.<C> Choice2<A,C>
biMapR(Fn1<? super B,? extends C> fn)
Covariantly map over the right parameter.<C> Choice2<A,C>
discardL(Applicative<C,Choice2<A,?>> appB)
Sequence both thisApplicative
andappB
, discarding thisApplicative's
result and returningappB
.<C> Choice2<A,B>
discardR(Applicative<C,Choice2<A,?>> appB)
Sequence both thisApplicative
andappB
, discardingappB's
result and returning thisApplicative
.<C> Choice3<A,B,C>
diverge()
Diverge this coproduct by introducing another possible type that it could represent.<C> Choice2<A,C>
flatMap(Fn1<? super B,? extends Monad<C,Choice2<A,?>>> f)
Chain dependent computations that may continue or short-circuit based on previous results.<C> Choice2<A,C>
fmap(Fn1<? super B,? extends C> fn)
Covariantly transmute this functor's parameter using the given mapping function.Choice2<B,A>
invert()
Swap the type parameters.<C> Lazy<Choice2<A,C>>
lazyZip(Lazy<? extends Applicative<Fn1<? super B,? extends C>,Choice2<A,?>>> lazyAppFn)
Given alazy
instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.Tuple2<Maybe<A>,Maybe<B>>
project()
Specialize this choice's projection to aTuple2
.<C> Choice2<A,C>
pure(C c)
Lift the valueb
into this applicative functor.static <A> Pure<Choice2<A,?>>
pureChoice()
<C> Choice2<A,C>
trampolineM(Fn1<? super B,? extends MonadRec<RecursiveResult<B,C>,Choice2<A,?>>> fn)
Given some operation yielding aRecursiveResult
inside thisMonadRec
, internally trampoline the operation until it yields atermination
instruction.<C,App extends Applicative<?,App>,TravB extends Traversable<C,Choice2<A,?>>,AppTrav extends Applicative<TravB,App>>
AppTravtraverse(Fn1<? super B,? extends Applicative<C,App>> fn, Fn1<? super TravB,? extends AppTrav> pure)
Applyfn
to each element of this traversable from left to right, and collapse the results into a single resulting applicative, potentially with the assistance of the applicative's pure function.<C> Choice2<A,C>
zip(Applicative<Fn1<? super B,? extends C>,Choice2<A,?>> appFn)
Given another instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.-
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface com.jnape.palatable.lambda.adt.coproduct.CoProduct2
embed, match, projectA, projectB
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Method Detail
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project
public Tuple2<Maybe<A>,Maybe<B>> project()
Specialize this choice's projection to aTuple2
.
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diverge
public final <C> Choice3<A,B,C> diverge()
Diverge this coproduct by introducing another possible type that it could represent. As no morphisms can be provided mapping current types to the new type, this operation merely acts as a convenience method to allow the use of a more convergent coproduct with a more divergent one; that is, if aCoProduct3<String, Integer, Boolean>
is expected, aCoProduct2<String, Integer>
should suffice.Generally, we use inheritance to make this a non-issue; however, with coproducts of differing magnitudes, we cannot guarantee variance compatibility in one direction conveniently at construction time, and in the other direction, at all. A
CoProduct2
could not be aCoProduct3
without specifying all type parameters that are possible for aCoProduct3
- more specifically, the third possible type - which is not necessarily known at construction time, or even useful if never used in the context of aCoProduct3
. The inverse inheritance relationship -CoProduct3
<CoProduct2
- is inherently unsound, as aCoProduct3
cannot correctly implementCoProduct2.match(com.jnape.palatable.lambda.functions.Fn1<? super A, ? extends R>, com.jnape.palatable.lambda.functions.Fn1<? super B, ? extends R>)
, given that the third typeC
is always possible.For this reason, there is a
diverge
method supported between allCoProduct
types of single magnitude difference.- Specified by:
diverge
in interfaceCoProduct2<A,B,Choice2<A,B>>
- Type Parameters:
C
- the additional possible type of this coproduct- Returns:
- a
CoProduct3
<A, B, C>
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fmap
public final <C> Choice2<A,C> fmap(Fn1<? super B,? extends C> fn)
Covariantly transmute this functor's parameter using the given mapping function. Generally this method is specialized to return an instance of the class implementing Functor.- Specified by:
fmap
in interfaceApplicative<A,B>
- Specified by:
fmap
in interfaceFunctor<A,B>
- Specified by:
fmap
in interfaceMonad<A,B>
- Specified by:
fmap
in interfaceMonadRec<A,B>
- Specified by:
fmap
in interfaceTraversable<A,B>
- Type Parameters:
C
- the new parameter type- Parameters:
fn
- the mapping function- Returns:
- a functor over B (the new parameter type)
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biMapL
public final <C> Choice2<C,B> biMapL(Fn1<? super A,? extends C> fn)
Covariantly map over the left parameter.- Specified by:
biMapL
in interfaceBifunctor<A,B,Choice2<?,?>>
- Specified by:
biMapL
in interfaceBoundedBifunctor<A,B,java.lang.Object,java.lang.Object,Choice2<?,?>>
- Type Parameters:
C
- the new left parameter type- Parameters:
fn
- the mapping function- Returns:
- a bifunctor over C (the new left parameter) and B (the same right parameter)
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biMapR
public final <C> Choice2<A,C> biMapR(Fn1<? super B,? extends C> fn)
Covariantly map over the right parameter. For all bifunctors that are also functors, it should hold thatbiMapR(f) == fmap(f)
.- Specified by:
biMapR
in interfaceBifunctor<A,B,Choice2<?,?>>
- Specified by:
biMapR
in interfaceBoundedBifunctor<A,B,java.lang.Object,java.lang.Object,Choice2<?,?>>
- Type Parameters:
C
- the new right parameter type- Parameters:
fn
- the mapping function- Returns:
- a bifunctor over A (the same left parameter) and C (the new right parameter)
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biMap
public final <C,D> Choice2<C,D> biMap(Fn1<? super A,? extends C> lFn, Fn1<? super B,? extends D> rFn)
Dually map covariantly over both the left and right parameters. This is isomorphic tobiMapL(lFn).biMapR(rFn)
.- Specified by:
biMap
in interfaceBifunctor<A,B,Choice2<?,?>>
- Specified by:
biMap
in interfaceBoundedBifunctor<A,B,java.lang.Object,java.lang.Object,Choice2<?,?>>
- Type Parameters:
C
- the new left parameter typeD
- the new right parameter type- Parameters:
lFn
- the left parameter mapping functionrFn
- the right parameter mapping function- Returns:
- a bifunctor over C (the new left parameter type) and D (the new right parameter type)
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zip
public <C> Choice2<A,C> zip(Applicative<Fn1<? super B,? extends C>,Choice2<A,?>> appFn)
Given another instance of this applicative over a mapping function, "zip" the two instances together using whatever application semantics the current applicative supports.
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lazyZip
public <C> Lazy<Choice2<A,C>> lazyZip(Lazy<? extends Applicative<Fn1<? super B,? extends C>,Choice2<A,?>>> lazyAppFn)
Given alazy
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.- Specified by:
lazyZip
in interfaceApplicative<A,B>
- Specified by:
lazyZip
in interfaceMonad<A,B>
- Specified by:
lazyZip
in interfaceMonadRec<A,B>
- Type Parameters:
C
- the resulting applicative parameter type- Parameters:
lazyAppFn
- the lazy other applicative instance- Returns:
- the mapped applicative
- See Also:
Maybe
,Either
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discardL
public <C> Choice2<A,C> discardL(Applicative<C,Choice2<A,?>> appB)
Sequence both thisApplicative
andappB
, discarding thisApplicative's
result and returningappB
. This is generally useful for sequentially performing side-effects.
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discardR
public <C> Choice2<A,B> discardR(Applicative<C,Choice2<A,?>> appB)
Sequence both thisApplicative
andappB
, discardingappB's
result and returning thisApplicative
. This is generally useful for sequentially performing side-effects.
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flatMap
public final <C> Choice2<A,C> flatMap(Fn1<? super B,? extends Monad<C,Choice2<A,?>>> f)
Chain dependent computations that may continue or short-circuit based on previous results.
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trampolineM
public <C> Choice2<A,C> trampolineM(Fn1<? super B,? extends MonadRec<RecursiveResult<B,C>,Choice2<A,?>>> fn)
Given some operation yielding aRecursiveResult
inside thisMonadRec
, internally trampoline the operation until it yields atermination
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.
- Specified by:
trampolineM
in interfaceMonadRec<A,B>
- Type Parameters:
C
- the ultimate resulting carrier type- Parameters:
fn
- the function to internally trampoline- Returns:
- the trampolined
MonadRec
- See Also:
for a basic implementation
,for a implementation
,for an implementation leveraging an already stack-safe
,for a implementation
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traverse
public <C,App extends Applicative<?,App>,TravB extends Traversable<C,Choice2<A,?>>,AppTrav extends Applicative<TravB,App>> AppTrav traverse(Fn1<? super B,? extends Applicative<C,App>> fn, Fn1<? super TravB,? extends AppTrav> pure)
Applyfn
to each element of this traversable from left to right, and collapse the results into a single resulting applicative, potentially with the assistance of the applicative's pure function.- Specified by:
traverse
in interfaceTraversable<A,B>
- Type Parameters:
C
- the resulting element typeApp
- the result applicative typeTravB
- this Traversable instance over BAppTrav
- the full inferred resulting type from the traversal- Parameters:
fn
- the function to applypure
- the applicative pure function- Returns:
- the traversed Traversable, wrapped inside an applicative
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a
public static <A,B> Choice2<A,B> a(A a)
Static factory method for wrapping a value of typeA
in aChoice2
.- Type Parameters:
A
- the first possible typeB
- the second possible type- Parameters:
a
- the value- Returns:
- the wrapped value as a
Choice2
<A, B>
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b
public static <A,B> Choice2<A,B> b(B b)
Static factory method for wrapping a value of typeB
in aChoice2
.- Type Parameters:
A
- the first possible typeB
- the second possible type- Parameters:
b
- the value- Returns:
- the wrapped value as a
Choice2
<A, B>
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