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package bjc.dicelang.ast;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import bjc.dicelang.IDiceExpression;
import bjc.dicelang.ast.nodes.DiceASTType;
import bjc.dicelang.ast.nodes.IDiceASTNode;
import bjc.dicelang.ast.nodes.LiteralDiceNode;
import bjc.dicelang.ast.nodes.OperatorDiceNode;
import static bjc.dicelang.ast.nodes.DiceASTType.*;
import bjc.utils.parserutils.AST;
/**
* Optimize an AST
*
* @author ben
*
*/
public class DiceASTOptimizer {
private static final class ArithmeticOperationCollapser
implements BinaryOperator<AST<IDiceASTNode>> {
private IDiceASTNode type;
private BiFunction<Integer, Integer, Integer> valueCollapser;
private boolean doSwap;
public ArithmeticOperationCollapser(IDiceASTNode type,
BiFunction<Integer, Integer, Integer> valueCollapser,
boolean doSwap) {
this.type = type;
this.valueCollapser = valueCollapser;
this.doSwap = doSwap;
}
@Override
public AST<IDiceASTNode> apply(AST<IDiceASTNode> leftAST,
AST<IDiceASTNode> rightAST) {
boolean isLeftConstant =
DiceASTOptimizer.checkNodeType(leftAST, LITERAL)
&& DiceASTOptimizer.isNodeConstant(leftAST);
boolean isRightConstant =
DiceASTOptimizer.checkNodeType(rightAST, LITERAL)
&& DiceASTOptimizer.isNodeConstant(leftAST);
if (isLeftConstant) {
if (isRightConstant) {
int combinedValue = valueCollapser.apply(
getNodeValue(leftAST), getNodeValue(rightAST));
return new AST<>(new LiteralDiceNode(combinedValue));
}
if (doSwap) {
return new AST<>(type, rightAST, leftAST);
}
}
return new AST<>(type, leftAST, rightAST);
}
}
private static Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>>
buildConstantCollapsers() {
Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>> operatorCollapsers =
new HashMap<>();
operatorCollapsers.put(OperatorDiceNode.ADD,
new ArithmeticOperationCollapser(OperatorDiceNode.ADD,
(leftVal, rightVal) -> leftVal + rightVal, true));
operatorCollapsers.put(OperatorDiceNode.SUBTRACT,
new ArithmeticOperationCollapser(OperatorDiceNode.SUBTRACT,
(leftVal, rightVal) -> leftVal - rightVal, false));
operatorCollapsers.put(OperatorDiceNode.DIVIDE,
new ArithmeticOperationCollapser(OperatorDiceNode.DIVIDE,
(leftVal, rightVal) -> leftVal / rightVal, false));
operatorCollapsers.put(OperatorDiceNode.MULTIPLY,
new ArithmeticOperationCollapser(OperatorDiceNode.MULTIPLY,
(leftVal, rightVal) -> leftVal * rightVal, true));
return null;
}
private static AST<IDiceASTNode> collapseLeaf(IDiceASTNode leaf) {
// Can't optimize a simple reference
if (leaf.getType() == VARIABLE) {
return new AST<>(leaf);
} else if (leaf.getType() == LITERAL) {
LiteralDiceNode node = (LiteralDiceNode) leaf;
return new AST<>(optimizeLiteral(node, node.toExpression()));
} else {
throw new UnsupportedOperationException(
"Found leaf operator. This isn't supported");
}
}
private static IDiceASTNode optimizeLiteral(LiteralDiceNode node,
IDiceExpression leaf) {
if (leaf.canOptimize()) {
return new LiteralDiceNode(Integer.toString(leaf.optimize()));
} else {
return node;
}
}
private static AST<IDiceASTNode> finishTree(AST<IDiceASTNode> tree) {
return tree;
}
/**
* Optimize a tree of expressions into a simpler form
*
* @param tree
* The tree to optimize
* @return The optimized tree
*/
public static AST<IDiceASTNode> optimizeTree(AST<IDiceASTNode> tree) {
AST<IDiceASTNode> astWithFoldedConstants =
tree.collapse(DiceASTOptimizer::collapseLeaf,
buildConstantCollapsers()::get,
DiceASTOptimizer::finishTree);
return astWithFoldedConstants;
}
private static boolean checkNodeType(AST<IDiceASTNode> ast,
DiceASTType type) {
return ast.applyToHead((node) -> node.getType()) == type;
}
private static boolean isNodeConstant(AST<IDiceASTNode> ast) {
return ast.applyToHead(
(node) -> ((LiteralDiceNode) node).isConstant());
}
private static int getNodeValue(AST<IDiceASTNode> ast) {
return ast.applyToHead(
(node) -> ((LiteralDiceNode) node).toConstant());
}
}
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