https://github.com/lambdacasserole/sugarsnap
Super generic and reusable shunting and parsing library.
https://github.com/lambdacasserole/sugarsnap
dijkstra expression infix-notation parser reverse-polish-notation shunting-yard-algorithm
Last synced: about 1 year ago
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Super generic and reusable shunting and parsing library.
- Host: GitHub
- URL: https://github.com/lambdacasserole/sugarsnap
- Owner: lambdacasserole
- License: mit
- Created: 2019-12-31T11:01:46.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2020-01-18T00:07:53.000Z (over 6 years ago)
- Last Synced: 2025-02-12T20:17:21.771Z (over 1 year ago)
- Topics: dijkstra, expression, infix-notation, parser, reverse-polish-notation, shunting-yard-algorithm
- Language: Java
- Size: 37.1 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Sugarsnap
Super generic and reusable shunting and parsing library.
## Overview
This library implements Dijkstra's [Shunting-yard algorithm](https://en.wikipedia.org/wiki/Shunting-yard_algorithm) in Java, with generics to permit the type-safe attachment of arbitrary objects to symbols.
The algorithm functions to convert mathematical expressions written in [infix notation](https://en.wikipedia.org/wiki/Infix_notation) to [reverse Polish notation (RPN)](https://en.wikipedia.org/wiki/Reverse_Polish_notation) for easy evaluation using a stack machine. Sugarsnap currenty supports:
* Functions
* Operator precedence
* Left/right operator associativity
* Parenthesised expressions
There is currently no support for:
* Function composition
* Variadic functions
* Postfix unary operators (e.g. factorial "!")
Mismatched brackets etc. will throw exceptions, which can be caught and handled.
## Usage
The purpose of this library is to convert infix notation to RPN. That is to say, it does not contain a tokeniser. Once you've wrangled your string into a list of tokens, here's a quick demonstration of what you need to do:
```java
// Expression: 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3
// Expression given as list of symbols with strings attached.
List> input = new LinkedList>(Arrays.asList(
new ShuntingYardNumber("3"), // A number.
// An operator, with precedence 2 and left associativity.
new ShuntingYardOperator("+", 2, true),
new ShuntingYardNumber("4"),
new ShuntingYardOperator("*", 3, true),
new ShuntingYardNumber("2"),
new ShuntingYardOperator("/", 3, true),
new ShuntingYardLeftParen("("), // An opening parenthesis.
new ShuntingYardNumber("1"),
new ShuntingYardOperator("-", 2, true),
new ShuntingYardNumber("5"),
new ShuntingYardRightParen(")"), // A closing parenthesis.
// Precedence 4 exponentiation operator with right associativity.
new ShuntingYardOperator("^", 4, false),
new ShuntingYardNumber("2"),
new ShuntingYardOperator("^", 4, false),
new ShuntingYardNumber("3")));
// Parse expression.
ShuntingYardParser parser = new ShuntingYardParser();
try {
List> output = parser.parse(input);
// Resulting list looks like this (as a string): "342*15-23^^/+"
// Do what you need to do with result...
} catch (ShuntingYardParserException e) {
// Exception encountered while parsing expression.
e.printStackTrace();
}
```