blob: ad148f89d84cf675b45ad173d1f603cdcfe3ce7e (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.indexinglanguage.expressions;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;
/**
* @author Simon Thoresen Hult
*/
public class MathResolver {
private final List<Item> items = new LinkedList<>();
public void push(ArithmeticExpression.Operator op, Expression exp) {
if (items.isEmpty() && op != ArithmeticExpression.Operator.ADD)
throw new IllegalArgumentException("First item in an arithmetic operation must be an addition, not " + op);
items.add(new Item(op, exp));
}
public Expression resolve() {
Deque<Item> stack = new ArrayDeque<>();
stack.push(items.remove(0));
while (!items.isEmpty()) {
Item item = items.remove(0);
while (stack.size() > 1 && stack.peek().op.precedes(item.op)) {
pop(stack);
}
stack.push(item);
}
while (stack.size() > 1) {
pop(stack);
}
return stack.pop().exp;
}
private void pop(Deque<Item> stack) {
Item rhs = stack.pop();
Item lhs = stack.peek();
lhs.exp = new ArithmeticExpression(lhs.exp, rhs.op, rhs.exp);
}
private static class Item {
final ArithmeticExpression.Operator op;
Expression exp;
Item(ArithmeticExpression.Operator op, Expression exp) {
this.op = Objects.requireNonNull(op);
this.exp = exp;
}
}
}
|
