christoph/lecture-compilers
1
Fork 0
Code Actions Activity

fix operator-precedence

Browse Source
This commit is contained in:
ChUrl
2020-12-14 15:04:52 +01:00
parent 63903f6955
commit bf6e2256d8
1 changed files with 60 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
src/main/java/parser/ast/ASTBalancer.java
View File

@ -1,13 +1,47 @@
package parser.ast;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import static util.Logger.log;
public final class ASTBalancer {
private static final Map<String, Integer> priority;
// 0 - Unary: -, +, !
// 1 - Multiplicative: *, /, %
// 2 - Additive: +, -
// 3 - Comparative: <, <=, >, >=
// 4 - Equality: ==, !=
// 5 - Logical AND: &&
// 6 - Logical OR: ||
static {
priority = new HashMap<>();
priority.put("NOT", 0);
priority.put("MUL", 1);
priority.put("DIV", 1);
priority.put("MOD", 1);
priority.put("ADD", 2);
priority.put("SUB", 2);
priority.put("LESS", 3);
priority.put("LESS_EQUAL", 3);
priority.put("GREATER", 3);
priority.put("GREATER_EQUAL", 3);
priority.put("EQUAL", 4);
priority.put("NOT_EQUAL", 4);
priority.put("AND", 5);
priority.put("OR", 6);
}
private ASTBalancer() {}
public static void balance(AST tree) {
@ -84,7 +118,7 @@ public final class ASTBalancer {
private static ASTNode getExpr(ASTNode root) {
for (ASTNode child : root.getChildren()) {
if (child.getName().equals("EXPR")) {
if ("EXPR".equals(child.getName())) {
return child;
}
}
@ -96,48 +130,47 @@ public final class ASTBalancer {
return root.getChildren().size() == 1;
}
// 0 - Unary: -, +, !
// 1 - Multiplicative: *, /, %
// 2 - Additive: +, -
// 3 - Comparative: <, <=, >, >=
// 4 - Equality: ==, !=
// 5 - Logical AND: &&
// 6 - Logical OR: ||
public static void operatorPrecedence(AST tree) {
log("Right-rotating expressions for operator-precedence");
operatorPrecedence(tree.getRoot());
boolean changed;
do {
changed = operatorPrecedence(tree.getRoot());
} while (changed);
}
public static void operatorPrecedence(ASTNode root) {
public static boolean operatorPrecedence(ASTNode root) {
boolean changed = false;
for (ASTNode child : root.getChildren()) {
operatorPrecedence(child);
changed = changed || operatorPrecedence(child);
if (preceding(root, child)) {
simpleRightRotate(root);
changed = true;
}
}
if (preceding(root)) {
simpleRightRotate(root);
}
return changed;
}
private static boolean preceding(ASTNode root) {
ASTNode op = getExpr(root);
if (op == null || !root.getName().equals("EXPR") || root.getValue().isEmpty()) {
private static boolean preceding(ASTNode parent, ASTNode child) {
if (!"EXPR".equals(parent.getName()) || parent.getValue().isEmpty()
|| !"EXPR".equals(child.getName()) || child.getValue().isEmpty()) {
return false;
}
Collection<String> arithHigh = Arrays.asList("MUL", "DIV", "MOD");
Collection<String> arithLow = Arrays.asList("ADD", "SUB");
Collection<String> logHigh = Arrays.asList("AND");
Collection<String> logLow = Arrays.asList("OR");
return (arithHigh.contains(root.getValue()) && arithLow.contains(op.getValue()))
|| (logHigh.contains(root.getValue()) && logLow.contains(op.getValue()));
// Less equals higher
return priority.get(parent.getValue()) < priority.get(child.getValue());
}
private static void simpleRightRotate(ASTNode root) {
ASTNode left = root.getChildren().get(0);
ASTNode right = root.getChildren().get(1);
log("Right-Rotating " + root.getName() + ": " + root.getValue());
ASTNode insertRight = new ASTNode(root.getName());
insertRight.setValue(root.getValue());
insertRight.setChildren(left.getChildren().get(1), right);