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/*
Copyright 2012-2022 Udo Klimaschewski
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.ezylang.evalex.parser;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import lombok.Value;
/**
* Expressions are parsed into an abstract syntax tree (AST). The tree has one root node and each
* node has zero or more children (parameters), depending on the operation. A leaf node is a
* numerical or string constant that has no more children (parameters). Other nodes define
* operators, functions and special operations like array index and structure separation.
*
* The tree is evaluated from bottom (leafs) to top, in a recursive way, until the root node is
* evaluated, which then holds the result of the complete expression.
*
*
To be able to visualize the tree, a toJSON method is provided. The produced JSON
* string can be used to visualize the tree. OE.g. with this online tool:
*
*
Online JSON to Tree Diagram Converter
*/
@Value
public class ASTNode {
/** The children od the tree. */
List parameters;
/** The token associated with this tree node. */
Token token;
public ASTNode(Token token, ASTNode... parameters) {
this.token = token;
this.parameters = Arrays.asList(parameters);
}
/**
* Produces a JSON string representation of this node ad all its children.
*
* @return A JSON string of the tree structure starting at this node.
*/
public String toJSON() {
if (parameters.isEmpty()) {
return String.format(
"{" + "\"type\":\"%s\",\"value\":\"%s\"}", token.getType(), token.getValue());
} else {
String childrenJson =
parameters.stream().map(ASTNode::toJSON).collect(Collectors.joining(","));
return String.format(
"{" + "\"type\":\"%s\",\"value\":\"%s\",\"children\":[%s]}",
token.getType(), token.getValue(), childrenJson);
}
}
}