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Eval.cs

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Eval.cs

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

0.11.0
NuGet
Version published
Maintainers
1
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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

dotnet add package Eval.cs

Usage

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

TypePropertyDescription
stringSrcthe expression
intOffsetthe offset before the error, specialy useful for pointing where the error has happened
intLengththe length of the wrong value or function
stringMessagethe cause of the exception, eg: "Closing unexsistent paren"

ArgumentAmountException

Means that the wrong of arguments was passed to a function

TypePropertyDescription
stringSrcsame as InvalidExpressionException
intOffsetsame as InvalidExpressionException
intLengthsame as InvalidExpressionException
stringMessagethe message: $"Function() expects Expected arguments but received Received"
stringFunctionname of the failed function
intExpectedexpected amount of arguments
intReceivedreceived 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

pow() expects 2 arguments but received 3
Math.Pow(1, 2, 3) - 4
^~~~~~~~~~~~~~~~^
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

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

EvalTest

Code to test the lexer, evaluation and exceptions.

Keywords

evaluator

FAQs

Package last updated on 19 Sep 2024

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