https://github.com/lucastavaresa/eval.cs

Mathematical expressions evaluator in csharp
https://github.com/lucastavaresa/eval.cs

c-sharp csharp csharp-library dotnet dotnet6 dotnet7 evaluator expression-evaluator expression-parser

Last synced: 28 days ago
JSON representation

Mathematical expressions evaluator in csharp

• Host: GitHub
• URL: https://github.com/lucastavaresa/eval.cs
• Owner: LucasTavaresA
• License: lgpl-3.0
• Created: 2023-04-20T23:11:50.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2024-08-14T04:54:15.000Z (5 months ago)
• Last Synced: 2024-08-14T19:35:24.571Z (5 months ago)
• Topics: c-sharp, csharp, csharp-library, dotnet, dotnet6, dotnet7, evaluator, expression-evaluator, expression-parser
• Language: C#
• Homepage: https://www.nuget.org/packages/Eval.cs
• Size: 143 KB
• Stars: 2
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

Awesome Lists containing this project

README

        
# Eval.cs

Mathematical expressions evaluator that supports math and enumerable functions, using only `System`,

from the lexer to the parser with no bizarre regex.

## Install

```console

dotnet add package Eval.cs

```

## Usage

```csharp

using System;

using Eval;

// csharp prefixes can be omitted and lower cased

Console.WriteLine(Evaluator.Evaluate("-2 + pi - Ceiling(3.2)"));

// Everything is called like functions

Console.WriteLine(Evaluator.Evaluate("IEnumerable.Average(2, 3, 5)"));

Console.WriteLine(Evaluator.Evaluate("pow(-average(2, 3, 5), -5)"));

Console.WriteLine(Evaluator.Evaluate("19e-11 /- 12");

Console.WriteLine(Evaluator.Evaluate("last(4, last(1, 2), 5)");

Console.WriteLine(Evaluator.Evaluate("921.315 * -20.93 % 34.567");

Console.WriteLine(Evaluator.Evaluate(" 9>>3  /+ 1.2");

```

## Exceptions

There are two custom exceptions, catch the rest as general exceptions that have a message

### InvalidExpressionException

Means that the passed string is not a valid expression

| Type     | Property  | Description                                                                            |

|:--------:|:---------:|:---------------------------------------------------------------------------------------|

| `string` | `Src`     | the expression                                                                         |

| `int`    | `Offset`  | the offset before the error, specialy useful for pointing where the error has happened |

| `int`    | `Length`  | the length of the wrong value or function                                              |

| `string` | `Message` | the cause of the exception, eg: "Closing unexsistent paren"                            |

### ArgumentAmountException

Means that the wrong of arguments was passed to a function

| Type     | Property   | Description                                                                        |

|:--------:|:----------:|:-----------------------------------------------------------------------------------|

| `string` | `Src`      | same as InvalidExpressionException                                                 |

| `int`    | `Offset`   | same as InvalidExpressionException                                                 |

| `int`    | `Length`   | same as InvalidExpressionException                                                 |

| `string` | `Message`  | the message:  $"`Function`() expects `Expected` arguments but received `Received`" |

| `string` | `Function` | name of the failed function                                                        |

| `int`    | `Expected` | expected amount of arguments                                                       |

| `int`    | `Received` | received amount of arguments                                                       |

### UnexpectedEvaluationException

Should not happen unless there is a logical problem with this evaluator

Throw like an general Exception that has a message

### Example

A text based exception

```console

pow() expects 2 arguments but received 3

Math.Pow(1, 2, 3) - 4

^~~~~~~~~~~~~~~~^

```

```csharp

using Eval;

using System;

static string ErrorMsg(string message, string src, int offset, int length)

{

    if (length < 1)

    {

        return $"{message}";

    }

    var marker = new string(' ', offset);

    if (length == 1)

    {

        marker += "^";

    }

    else if (length == 2)

    {

        marker += "^^";

    }

    else if (length > 2)

    {

        marker += $"^{new('~', length - 2)}^";

    }

    return $"{message}\n{src}\n{marker}";

}

try

{

    var result = Evaluator.Evaluate("Math.Pow(1, 2, 3) - 4");

}

catch (Exception e)

{

    Console.WriteLine(

        e switch

        {

            InvalidExpressionException ie => ErrorMsg(ie.Message, ie.Src, ie.Offset, ie.Length),

            ArgumentAmountException ae => ErrorMsg(ae.Message, ae.Src, ae.Offset, ae.Length),

            _ => e.Message

        }

    );

}

```

## [ExprGen](./ExprGen/Program.cs)

Generates simple math expressions, does not generate functions and parens.

## [EvalTest](./EvalTest/Program.cs)

Code to test the lexer, evaluation and exceptions.