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https://github.com/devtony101/infix-expression-parser
A dart package to help you parse and evaluate infix mathematical expressions into their prefix and postfix notations.
https://github.com/devtony101/infix-expression-parser
dart dart-library dart-package flutter parser parser-library side-project
Last synced: about 2 months ago
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A dart package to help you parse and evaluate infix mathematical expressions into their prefix and postfix notations.
- Host: GitHub
- URL: https://github.com/devtony101/infix-expression-parser
- Owner: DevTony101
- License: bsd-3-clause
- Created: 2022-01-16T23:46:38.000Z (almost 3 years ago)
- Default Branch: main
- Last Pushed: 2022-01-17T01:47:18.000Z (almost 3 years ago)
- Last Synced: 2024-04-20T13:06:06.139Z (9 months ago)
- Topics: dart, dart-library, dart-package, flutter, parser, parser-library, side-project
- Language: Dart
- Homepage:
- Size: 25.4 KB
- Stars: 2
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
[](https://github.com/DevTony101/gasteroids/blob/main/LICENSE)
A dart package to help you parse and evaluate infix mathematical expressions into their prefix and postfix notations.
## Features
- Convert an infix expression into its prefix and postfix notations
- Evaluate a mathematical expression
- Support for basic mathematical operations
## Usage
You can use `infix-expression-parser` as a library or as a CLI tool. Below are some examples explaining how to use the package in each case.
### As a library
The package exposes two main classes:
- **InfixExpressionConverter**: Use this class when you have an infix expression and want to convert it either to its postfix or infix notation.
- **ExpressionEvaluator**: Use this class when you already have a postfix or prefix expression and want to evaluate it to a result. Use in combination with `InfixExpressionConverter` to also evaluate infix expressions easily. Note that in order to return a value, you need to provide a **context** in which you give each symbol in the expression a numeric value.
#### Example #1: Converting an infix expression
```dart
import 'package:infix_expression_parser/infix_expression_converter.dart';
void main() {
// Provide an infix expression
const infixExpression = '(a-b+c)*(d+e*f)';
// Create an instance of InfixExpressionConverter
final converter = InfixExpressionConverter(expression: infixExpression);
final postfixExpression = converter.toPostfixNotation();
final prefixExpression = converter.toPrefixNotation();
print(postfixExpression); // ab-c+def*+*
print(prefixExpression); // *+-abc+d*ef
}
```
#### Example #2: Evaluating a postfix expression
```dart
import 'package:infix_expression_parser/expression_evaluator.dart';
void main() {
// Define a context map
const context = {'a': 2, 'b': 3, 'c': 4, 'd': 5};
// Provide a postfix expression
const postfixExpression = 'abc+*d/';
// Use the static method provided by the ExpressionEvaluator class and pass both the expression and the context
final value = ExpressionEvaluator.evaluatePostfix(expression: postfixExpression, context: context);
print(value); // 2.8
}
```
#### Example #3: Evaluating a prefix expression
```dart
import 'package:infix_expression_parser/expression_evaluator.dart';
void main() {
// Define a context map
const context = {'a': 2, 'b': 3, 'c': 4, 'd': 5, 'e': 6};
// Provide a postfix expression
const prefixExpression = '*-a/bc-/ade';
// Use the static method provided by the ExpressionEvaluator class and pass both the expression and the context
final value = ExpressionEvaluator.evaluatePrefix(expression: prefixExpression, context: context);
print(value); // -7.0
}
```
#### Example #4: Evaluating an infix expression
```dart
import 'package:infix_expression_parser/infix_expression_converter.dart';
import 'package:infix_expression_parser/expression_evaluator.dart';
void main() {
// Provide an infix expression
const infixExpression = 'a-b+c-d*e';
// Convert it to either its postfix or prefix notation
final converter = InfixExpressionConverter(expression: infixExpression);
final postfixExpression = converter.toPostfixNotation();
// Define a context map
const context = {'a': 2, 'b': 3, 'c': 4, 'd': 5, 'e': 6};
// Use the static method provided by the ExpressionEvaluator class and pass both the expression and the context
final value = ExpressionEvaluator.evaluatePostfix(expression: postfixExpression, context: context);
print(value); // -27.0
}
```
### As a CLI tool
The package expose a `infix-parser` command explained below:
```bash
A CLI tool for evaluating expressions in prefix or postfix notations or converting infix expressions.
Usage: infix-parser [arguments]
Global options:
-h, --help Print this usage information.
Available commands:
convert Converts an expression to its prefix or postfix notation
Run "infix-parser help " for more information about a command.
```
You can use the `convert` sub-command to parse infix expressions.
#### Example #1: Converting an infix expression to a prefix expression
```bash
pub run infix_expression_parser:main convert '(a-b/c)*(a/d-e)' --prefix
*-a/bc-/ade
```
#### Example #2: Converting an infix expression to a postfix expression
```bash
pub run infix_expression_parser:main convert '(a-b/c)*(a/d-e)' --postfix
abc/-ad/e-*
```
## Future improvements
- A sub-command for evaluating expressions in the command line may come in future iterations of this package
- Support for other mathematical operations, functions and symbols may come come in future iterations of this package