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Add Trampoline.suspend(final F0<Trampoline<A>> a).
1 parent 9b1651b commit d3d876c

6 files changed

Lines changed: 22 additions & 13 deletions

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‎core/src/main/java/fj/control/Trampoline.java‎

Lines changed: 14 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -46,7 +46,7 @@ public <R> R fold(final F<Normal<A>, R> n,
4646
// The monadic bind constructs a new Codense whose subcomputation is still `sub`, and Kleisli-composes the
4747
// continuations.
4848
public <B> Trampoline<B> bind(final F<A, Trampoline<B>> f) {
49-
return codense(sub, o -> suspend(P.lazy(() -> cont.f(o).bind(f))));
49+
return codense(sub, o -> suspend(() -> cont.f(o).bind(f)));
5050
}
5151

5252
// The resumption of a Codense is the resumption of its subcomputation. If that computation is done, its result
@@ -126,6 +126,16 @@ public static <A> Trampoline<A> pure(final A a) {
126126
return new Pure<>(a);
127127
}
128128

129+
/**
130+
* Suspends the given computation in a thunk.
131+
*
132+
* @param a A trampoline suspended in a thunk.
133+
* @return A trampoline whose next step runs the given thunk.
134+
*/
135+
public static <A> Trampoline<A> suspend(final F0<Trampoline<A>> a) {
136+
return new Suspend<>(P.lazy(a));
137+
}
138+
129139
/**
130140
* Suspends the given computation in a thunk.
131141
*
@@ -136,6 +146,7 @@ public static <A> Trampoline<A> suspend(final P1<Trampoline<A>> a) {
136146
return new Suspend<>(a);
137147
}
138148

149+
139150
/**
140151
* @return The first-class version of `suspend`.
141152
*/
@@ -255,15 +266,15 @@ public final <B, C> Trampoline<C> zipWith(final Trampoline<B> b, final F2<A, B,
255266
final Either<P1<Trampoline<B>>, B> eb = b.resume();
256267
for (final P1<Trampoline<A>> x : ea.left()) {
257268
for (final P1<Trampoline<B>> y : eb.left()) {
258-
return suspend(x.bind(y, F2Functions.curry((ta, tb) -> suspend(P.lazy(() -> ta.zipWith(tb, f))))));
269+
return suspend(x.bind(y, F2Functions.curry((ta, tb) -> suspend(() -> ta.zipWith(tb, f)))));
259270
}
260271
for (final B y : eb.right()) {
261272
return suspend(x.map(ta -> ta.map(F2Functions.f(F2Functions.flip(f), y))));
262273
}
263274
}
264275
for (final A x : ea.right()) {
265276
for (final B y : eb.right()) {
266-
return suspend(P.lazy(() -> pure(f.f(x, y))));
277+
return suspend(() -> pure(f.f(x, y)));
267278
}
268279
for (final P1<Trampoline<B>> y : eb.left()) {
269280
return suspend(y.map(liftM2(F2Functions.curry(f)).f(pure(x))));

‎core/src/main/java/fj/data/DList.java‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -126,6 +126,6 @@ public DList<A> append(DList<A> other) {
126126
}
127127

128128
private static <A,B,C> F<A,Trampoline<C>> kleisliTrampCompose(F<B,Trampoline<C>> bc, F<A,Trampoline<B>> ab) {
129-
return (A a) -> ab.f(a).bind((B b) -> Trampoline.suspend(P.lazy(() -> bc.f(b))));
129+
return (A a) -> ab.f(a).bind((B b) -> Trampoline.suspend(() -> bc.f(b)));
130130
}
131131
}

‎core/src/main/java/fj/data/Eval.java‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -204,7 +204,7 @@ private static final class PureTrampolineEval<A> extends TrampolineEval<A> {
204204

205205
@Override
206206
protected final Trampoline<A> trampoline() {
207-
return Trampoline.suspend(P.lazy(() -> Trampoline.pure(start.value())));
207+
return Trampoline.suspend(() -> Trampoline.pure(start.value()));
208208
}
209209
}
210210

@@ -219,7 +219,7 @@ private static final class BindTrampolineEval<A, B> extends TrampolineEval<B> {
219219

220220
@Override
221221
protected final Trampoline<B> trampoline() {
222-
return Trampoline.suspend(P.lazy(() -> next.trampoline().bind(v -> f.f(v).asTrampoline().trampoline())));
222+
return Trampoline.suspend(() -> next.trampoline().bind(v -> f.f(v).asTrampoline().trampoline()));
223223
}
224224
}
225225

@@ -232,7 +232,7 @@ private static final class DeferEval<A> extends TrampolineEval<A> {
232232

233233
@Override
234234
protected final Trampoline<A> trampoline() {
235-
return Trampoline.suspend(P.lazy(() -> memo._1().asTrampoline().trampoline()));
235+
return Trampoline.suspend(() -> memo._1().asTrampoline().trampoline());
236236
}
237237
}
238238
}

‎core/src/main/java/fj/data/List.java‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -736,7 +736,7 @@ public final <B> B foldRight(final F2<A, B, B> f, final B b) {
736736
* @return A Trampoline containing the final result after the right-fold reduction.
737737
*/
738738
public final <B> Trampoline<B> foldRightC(final F2<A, B, B> f, final B b) {
739-
return Trampoline.suspend(P.lazy(() -> isEmpty() ? Trampoline.pure(b) : tail().foldRightC(f, b).map(F2Functions.f(f, head()))));
739+
return Trampoline.suspend(() -> isEmpty() ? Trampoline.pure(b) : tail().foldRightC(f, b).map(F2Functions.f(f, head())));
740740
}
741741

742742
/**

‎core/src/main/java/fj/data/State.java‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,6 @@
55
import fj.Unit;
66
import fj.control.Trampoline;
77

8-
import static fj.P.lazy;
98
import static fj.P.p;
109
import static fj.control.Trampoline.suspend;
1110
import static fj.data.List.cons;
@@ -75,7 +74,7 @@ public static <S, A, B> State<S, List<B>> traverse(List<A> list, F<A, State<S, B
7574
}
7675

7776
private static <S, A> State<S, A> suspended(F<S, Trampoline<P2<S, A>>> runF) {
78-
return new State<>(s -> suspend(lazy(() -> runF.f(s))));
77+
return new State<>(s -> suspend(() -> runF.f(s)));
7978
}
8079

8180
private final F<S, Trampoline<P2<S, A>>> runF;

‎quickcheck/src/main/java/fj/test/Gen.java‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@
1616
import static fj.Function.flip;
1717
import static fj.Monoid.intAdditionMonoid;
1818
import static fj.Ord.intOrd;
19-
import static fj.P.lazy;
2019
import static fj.P2.__1;
2120
import static fj.control.Trampoline.pure;
2221
import static fj.control.Trampoline.suspend;
@@ -551,15 +550,15 @@ final class Tramp {
551550

552551
// Picks elements in constant stack space
553552
private Trampoline<List<A>> tramp(List<A> remainAs, int remainN, int remainALength) {
554-
return suspend(lazy(() ->
553+
return suspend(() ->
555554
(remainN == 0) ?
556555
// We have picked N elements; stop
557556
pure(nil()) :
558557
// For M remaining elements of which N will be picked, pick remainAs.head() with probability N/M
559558
(r.choose(0, remainALength - 1) < remainN) ?
560559
tramp(remainAs.tail(), remainN - 1, remainALength - 1)
561560
.map(pickedTail -> cons(remainAs.head(), pickedTail)) :
562-
tramp(remainAs.tail(), remainN, remainALength - 1)));
561+
tramp(remainAs.tail(), remainN, remainALength - 1));
563562
}
564563

565564
}

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