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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 <T> The type contained in the tree.
*
* @param tre The tree to outline.
* @param leafMarker The path to mark nodes with.
*
* @return The list of marked paths. */
public static <T> ListEx<ListEx<T>> outlineTree(Tree<T> tre, Predicate<T> leafMarker) {
ListEx<ListEx<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(Tree<T> subtree, LinkedList<T> path,
Predicate<T> leafMarker, ListEx<ListEx<T>> paths) {
if (subtree.getChildrenCount() == 0 && leafMarker.test(subtree.getHead())) {
/* We're at a matching leaf node. Add it. */
ListEx<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> Tree<ContainedType> substitute(
Tree<ContainedType> tree,
Predicate<ContainedType> marker,
Function<ContainedType, Tree<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> Tree<ContainedType> substitute(
Tree<ContainedType> tree,
MapEx<ContainedType, Tree<ContainedType>> environment) {
return substitute(
tree,
environment::containsKey,
(element) -> environment.get(element).get());
}
}
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