From 843329de434bb334d90927c4d22345373a388530 Mon Sep 17 00:00:00 2001
From: bculkin2442 <bjculkin@mix.wvu.edu>
Date: Tue, 2 Jul 2019 18:05:22 -0400
Subject: Rename package root

The package root is now bjc, not io.github.bculkin2442.
---
 src/main/java/bjc/funcdata/theory/Bifunctor.java | 176 +++++++++++++++++++++++
 src/main/java/bjc/funcdata/theory/Functor.java   |  43 ++++++
 2 files changed, 219 insertions(+)
 create mode 100644 src/main/java/bjc/funcdata/theory/Bifunctor.java
 create mode 100644 src/main/java/bjc/funcdata/theory/Functor.java

(limited to 'src/main/java/bjc/funcdata/theory')

diff --git a/src/main/java/bjc/funcdata/theory/Bifunctor.java b/src/main/java/bjc/funcdata/theory/Bifunctor.java
new file mode 100644
index 0000000..b576a2b
--- /dev/null
+++ b/src/main/java/bjc/funcdata/theory/Bifunctor.java
@@ -0,0 +1,176 @@
+package bjc.funcdata.theory;
+
+import java.util.function.Function;
+
+/**
+ * A functor over a pair of heterogeneous types.
+ *
+ * @author ben
+ *
+ * @param <LeftType>
+ *        The type stored on the 'left' of the pair.
+ *
+ * @param <RightType>
+ *        The type stored on the 'right' of the pair.
+ */
+public interface Bifunctor<LeftType, RightType> {
+	/**
+	 * Alias for functor mapping.
+	 *
+	 * @author EVE
+	 *
+	 * @param <OldLeft>
+	 *        The old left type.
+	 *
+	 * @param <OldRight>
+	 *        The old right type.
+	 *
+	 * @param <NewLeft>
+	 *        The new left type.
+	 *
+	 * @param <NewRight>
+	 *        The new right type.
+	 */
+	public interface BifunctorMap<OldLeft, OldRight, NewLeft, NewRight>
+			extends Function<Bifunctor<OldLeft, OldRight>, Bifunctor<NewLeft, NewRight>> {
+		/*
+		 * Alias
+		 */
+	}
+
+	/**
+	 * Alias for left functor mapping.
+	 *
+	 * @author EVE
+	 *
+	 * @param <OldLeft>
+	 *        The old left type.
+	 *
+	 * @param <OldRight>
+	 *        The old right type.
+	 *
+	 * @param <NewLeft>
+	 *        The new left type.
+	 */
+	public interface LeftBifunctorMap<OldLeft, OldRight, NewLeft>
+			extends BifunctorMap<OldLeft, OldRight, NewLeft, OldRight> {
+		/*
+		 * Alias
+		 */
+	}
+
+	/**
+	 * Alias for right functor mapping.
+	 *
+	 * @author EVE
+	 *
+	 * @param <OldLeft>
+	 *        The old left type.
+	 *
+	 * @param <OldRight>
+	 *        The old right type.
+	 *
+	 * @param <NewRight>
+	 *        The new right type.
+	 */
+	public interface RightBifunctorMap<OldLeft, OldRight, NewRight>
+			extends BifunctorMap<OldLeft, OldRight, OldLeft, NewRight> {
+		/*
+		 * Alias
+		 */
+	}
+
+	/**
+	 * Lift a pair of functions to a single function that maps over both
+	 * parts of a pair.
+	 *
+	 * @param <OldLeft>
+	 *        The old left type of the pair.
+	 *
+	 * @param <OldRight>
+	 *        The old right type of the pair.
+	 *
+	 * @param <NewLeft>
+	 *        The new left type of the pair.
+	 *
+	 * @param <NewRight>
+	 *        The new right type of the pair.
+	 *
+	 * @param leftFunc
+	 *        The function that maps over the left of the pair.
+	 *
+	 * @param rightFunc
+	 *        The function that maps over the right of the pair.
+	 *
+	 * @return A function that maps over both parts of the pair.
+	 */
+	public default <OldLeft, OldRight, NewLeft, NewRight> BifunctorMap<OldLeft, OldRight, NewLeft, NewRight> bimap(
+			final Function<OldLeft, NewLeft> leftFunc, final Function<OldRight, NewRight> rightFunc) {
+		final BifunctorMap<OldLeft, OldRight, NewLeft, NewRight> bimappedFunc = (argPair) -> {
+			final LeftBifunctorMap<OldLeft, OldRight, NewLeft> leftMapper = argPair.fmapLeft(leftFunc);
+
+			final Bifunctor<NewLeft, OldRight> leftMappedFunctor = leftMapper.apply(argPair);
+			final RightBifunctorMap<NewLeft, OldRight, NewRight> rightMapper = leftMappedFunctor
+					.fmapRight(rightFunc);
+
+			return rightMapper.apply(leftMappedFunctor);
+		};
+
+		return bimappedFunc;
+	}
+
+	/**
+	 * Lift a function to operate over the left part of this pair.
+	 *
+	 * @param <OldLeft>
+	 *        The old left type of the pair.
+	 *
+	 * @param <OldRight>
+	 *        The old right type of the pair.
+	 *
+	 * @param <NewLeft>
+	 *        The new left type of the pair.
+	 *
+	 * @param func
+	 *        The function to lift to work over the left side of the pair.
+	 *
+	 * @return The function lifted to work over the left side of bifunctors.
+	 */
+	public <OldLeft, OldRight, NewLeft> LeftBifunctorMap<OldLeft, OldRight, NewLeft> fmapLeft(
+			Function<OldLeft, NewLeft> func);
+
+	/**
+	 * Lift a function to operate over the right part of this pair.
+	 *
+	 * @param <OldLeft>
+	 *        The old left type of the pair.
+	 *
+	 * @param <OldRight>
+	 *        The old right type of the pair.
+	 *
+	 * @param <NewRight>
+	 *        The new right type of the pair.
+	 *
+	 * @param func
+	 *        The function to lift to work over the right side of the pair.
+	 *
+	 * @return The function lifted to work over the right side of
+	 *         bifunctors.
+	 */
+	public <OldLeft, OldRight, NewRight> RightBifunctorMap<OldLeft, OldRight, NewRight> fmapRight(
+			Function<OldRight, NewRight> func);
+
+	/**
+	 * Get the value contained on the left of this bifunctor.
+	 *
+	 * @return The value on the left side of this bifunctor.
+	 */
+	public LeftType getLeft();
+
+	/**
+	 * Get the value contained on the right of this bifunctor.
+	 *
+	 * @return The value on the right of this bifunctor.
+	 */
+	public RightType getRight();
+}
diff --git a/src/main/java/bjc/funcdata/theory/Functor.java b/src/main/java/bjc/funcdata/theory/Functor.java
new file mode 100644
index 0000000..4192bf4
--- /dev/null
+++ b/src/main/java/bjc/funcdata/theory/Functor.java
@@ -0,0 +1,43 @@
+package bjc.funcdata.theory;
+
+import java.util.function.Function;
+
+/**
+ * Represents a container or context some sort usually, but the precise
+ * definition is that it represents exactly what it is defined as.
+ *
+ * @author ben
+ *
+ * @param <ContainedType>
+ *        The value inside the functor.
+ */
+public interface Functor<ContainedType> {
+	/**
+	 * Converts a normal function to operate over values in a functor..
+	 *
+	 * N.B: Even though the type signature implies that you can apply the
+	 * resulting function to any type of functor, it is only safe to call it
+	 * on instances of the type of functor you called fmap on..
+	 *
+	 * @param <ArgType>
+	 *        The argument of the function.
+	 *
+	 * @param <ReturnType>
+	 *        The return type of the function.
+	 *
+	 * @param func
+	 *        The function to convert.
+	 *
+	 * @return The passed in function converted to work over a particular
+	 *         type of functors.
+	 */
+	public <ArgType, ReturnType> Function<Functor<ArgType>, Functor<ReturnType>> fmap(
+			Function<ArgType, ReturnType> func);
+
+	/**
+	 * Retrieve the thing inside this functor.
+	 *
+	 * @return The thing inside this functor.
+	 */
+	public ContainedType getValue();
+}
-- 
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