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package bjc.utils.funcutils;
import java.util.LinkedList;
import java.util.function.*;
import bjc.data.*;
import bjc.funcdata.*;
/**
* Implements various utilities for trees.
*
* @author Benjamin Culkin
*/
public class TreeUtils {
/**
* Convert a tree into a list of outline nodes that match a certain path.
*
* @param tre
* The tree to outline.
* @param leafMarker
* The path to mark nodes with.
* @return The list of marked paths.
*/
public static <T> IList<IList<T>> outlineTree(ITree<T> tre, Predicate<T> leafMarker) {
IList<IList<T>> paths = new FunctionalList<>();
LinkedList<T> path = new LinkedList<>();
path.add(tre.getHead());
tre.doForChildren(child -> findPath(child, path, leafMarker, paths));
return paths;
}
/* Find a path in a tree. */
private static <T> void findPath(ITree<T> subtree, LinkedList<T> path,
Predicate<T> leafMarker, IList<IList<T>> paths) {
if (subtree.getChildrenCount() == 0 && leafMarker.test(subtree.getHead())) {
/* We're at a matching leaf node. Add it. */
IList<T> finalPath = new FunctionalList<>();
for (T ePath : path) finalPath.add(ePath);
finalPath.add(subtree.getHead());
paths.add(finalPath);
} else {
/* Check the children of this node. */
path.add(subtree.getHead());
subtree.doForChildren(child -> findPath(child, path, leafMarker, paths));
path.removeLast();
}
}
/**
* Performs 'variable substitution' or something along those lines on a tree.
*
* @param <ContainedType> The type of element contained in the tree.
* @param tree The tree to do expansion in.
* @param marker The function to mark which nodes should be expanded.
* @param expander The function to expand nodes.
* @return A transformed copy of the tree.
*/
public static <ContainedType> ITree<ContainedType> substitute(
ITree<ContainedType> tree,
Predicate<ContainedType> marker,
Function<ContainedType, ITree<ContainedType>> expander) {
tree.topDownTransform((contents) -> {
if (marker.test(contents)) return TopDownTransformResult.TRANSFORM;
else return TopDownTransformResult.PASSTHROUGH;
}, (node) -> {
return expander.apply(node.getHead());
});
return tree;
}
/**
* Performs 'variable substitution' or something along those lines on a tree.
*
* @param <ContainedType> The type of element contained in the tree.
* @param tree The tree to do expansion in.
* @param environment A map which contains the variables to substitute.
* @return A transformed copy of the tree.
*/
public static <ContainedType> ITree<ContainedType> substitute(
ITree<ContainedType> tree,
IMap<ContainedType, ITree<ContainedType>> environment) {
return substitute(tree, environment::containsKey, environment::get);
}
}
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