| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| ComposedContinuation.java | 100% | 100% | 100% | 100% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.recur; | |
| 36 | ||
| 37 | import edu.rice.cs.plt.lambda.Lambda; | |
| 38 | ||
| 39 | /** | |
| 40 | * A continuation defined in terms of two other continuations, where the second is parameterized | |
| 41 | * by the result of the first. This class is essential to correctly handling general recursion. | |
| 42 | * Its {@link #step} and {@link #compose} methods are defined so that iterative computation | |
| 43 | * does not require "drilling down" to an unbounded depth in order to locate and perform the | |
| 44 | * next evaluation step. | |
| 45 | */ | |
| 46 | public class ComposedContinuation<T, R> extends PendingContinuation<R> { | |
| 47 | ||
| 48 | private final Continuation<? extends T> _first; | |
| 49 | private final Lambda<? super T, ? extends Continuation<? extends R>> _rest; | |
| 50 | ||
| 51 | 4101 | public ComposedContinuation(Continuation<? extends T> first, |
| 52 | Lambda<? super T, ? extends Continuation<? extends R>> rest) { | |
| 53 | 4101 | _first = first; |
| 54 | 4101 | _rest = rest; |
| 55 | } | |
| 56 | ||
| 57 | /** | |
| 58 | * If {@code first} is resolved, apply {@code rest} to compute the second. Otherwise, | |
| 59 | * invoke {@code first.step()}, and then "push" {@code rest} into the result by invoking | |
| 60 | * {@code compose()}. | |
| 61 | */ | |
| 62 | 2571 | public Continuation<? extends R> step() { |
| 63 | 1549 | if (_first.isResolved()) { return _rest.value(_first.value()); } |
| 64 | 1022 | else { return _first.step().compose(_rest); } |
| 65 | } | |
| 66 | ||
| 67 | /** | |
| 68 | * Create a new {@code ComposedContinuation} with the same {@code first}, but with a {@code rest} | |
| 69 | * that will compose {@code c} onto the result of this object's {@code rest} function. | |
| 70 | * (Note that the default behavior -- nesting this object in another {@code ComposedContinuation} | |
| 71 | * with {@code c} as its {@code rest} -- results in continuations whose {@code step()} methods | |
| 72 | * are invoked recursively to an unbounded depth.) | |
| 73 | */ | |
| 74 | 1530 | public <S> Continuation<S> compose(final Lambda<? super R, ? extends Continuation<? extends S>> c) { |
| 75 | 1530 | return new ComposedContinuation<T, S>(_first, new Lambda<T, Continuation<? extends S>>() { |
| 76 | 1530 | public Continuation<? extends S> value(T arg) { |
| 77 | 1530 | return _rest.value(arg).compose(c); |
| 78 | } | |
| 79 | }); | |
| 80 | } | |
| 81 | ||
| 82 | } |
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