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flip commutative exprs for stack efficiency

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2021-01-23 18:36:03 +01:00
parent 4f9c4364e5
commit 60452b3713
1 changed files with 25 additions and 0 deletions
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25
src/main/java/parser/ast/ASTBalancer.java
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@ -10,6 +10,7 @@ public final class ASTBalancer {
private static final Map<String, Integer> priority;
private static final Set<String> unary;
private static final Set<String> commutative;
//!: Operatorpräzedenz
// 0 - Unary: -, +, !
@ -36,6 +37,8 @@ public final class ASTBalancer {
Map.entry("OR", 6));
unary = Set.of("NOT", "ADD", "SUB");
commutative = Set.of("ADD", "MUL", "EQUAL", "NOT_EQUAL", "AND", "OR");
}
private ASTBalancer() {}
@ -44,6 +47,7 @@ public final class ASTBalancer {
flip(tree);
leftPrecedence(tree);
operatorPrecedence(tree);
flipCommutativeExpr(tree);
log(tree.toString());
log("-".repeat(100));
@ -65,6 +69,27 @@ public final class ASTBalancer {
Collections.reverse(root.getChildren());
}
public static void flipCommutativeExpr(AST tree) {
log("Flipping commutative expressions for stack efficiency");
flipCommutativeExpr(tree.getRoot());
}
private static void flipCommutativeExpr(ASTNode root) {
for (ASTNode child : root.getChildren()) {
flipCommutativeExpr(child);
}
if ("expr".equals(root.getName()) && commutative.contains(root.getValue())) {
if (root.getChildren().size() == 2 && root.getChildren().get(0).size() < root.getChildren().get(1).size()) {
// Make the bigger subtree the left one
log("Flipping " + root.getName() + ": " + root.getValue() + " for stack efficiency.");
log(root.toString());
Collections.reverse(root.getChildren());
}
}
}
// Führt Linksrotationen durch
// Es werden EXPR-Nodes (2 Childs, 1 davon EXPR, Kein Wert) solange wie möglich linksrotiert
public static void leftPrecedence(AST tree) {