# Math Expression Evaluator in .NET

Overview

MathEvaluator is a .NET library that allows you to evaluate and compile any mathematical expressions from a string dynamically.

Features

• Supports different mathematical contexts, such as scientific, programming, and other custom contexts.
• Evaluates to double, boolean, or decimal.
• Compiles a math expression string into executable code and produces a delegate that represents the math expression.
• Provides variable support within math expressions.
• Extensible with custom functions and operators.
• Fast and comprehensive. More than 1300 tests are passed, including complex math expressions (for example, -3^4sin(-π/2) or sin-3/cos1).

Articles

Evaluating Boolean logical expressions.

Compilation of a Math Expression into a delegate.

Installation

dotnet add package MathEvaluator

Alternatively, you can install the package using the NuGet Package Manager Console:

Install-Package MathEvaluator

Perfomance

This math expression evaluator is designed for exceptional performance by leveraging modern .NET features and best practices, which is why it targets .NET Standard 2.1 or higher.

This high-performance evaluator stands out due to its use of ReadOnlySpan<char>, and avoidance of regular expressions. These design choices collectively ensure minimal memory allocation, fast parsing, and efficient execution.

The evaluator uses recursive method calls to handle mathematical operations based on operator precedence and rules, an operator with highest precedence is evaluating first. This approach avoids the overhead associated with stack or queue data structures.

The evaluator uses a prefix tree, also known as a trie (pronounced "try"), for efficient searching of variables, operators, and functions by their keys (names) when providing a specific mathematical context or adding custom variables, operators, and functions is required.

Let's compare, for example, performance of calculating the mathematical expression:

22888.32 * 30 / 323.34 / .5 - -1 / (2 + 22888.32) * 4 - 6

Below are the results of the comparison with the NCalc library:

NOTE: NCalc includes built-in caching, enabled by default in recent versions. While this can improve benchmark performance, in real-world scenarios, caching may increase memory usage and is not effective if the evaluation results depend on variable values. In such cases, compilation is a better alternative.

Compilation

Added in version 2.0.0

By using compilation, you can convert any mathematical expression string into a delegate, such as Func\<T, TResult> or Func\, which significantly improves performance when evaluating the expression. However, since compilation takes time, it is beneficial to compile the expression beforehand if you plan to evaluate it multiple times, especially for 200 or more iterations. Refer to the benchmarks for detailed performance insights.

How to use

Examples of using string extentions:

"22888.32 * 30 / 323.34 / .5 - -1 / (2 + 22888.32) * 4 - 6".Evaluate();

"22888.32 * 30 / 323.34 / .5 - -1 / (2 + 22888.32) * 4 - 6".EvaluateDecimal();

"$22,888.32 * 30 / 323.34 / .5 - - 1 / (2 + $22,888.32) * 4 - 6".Evaluate(null, new CultureInfo("en-US"));

"22’888.32 CHF * 30 / 323.34 / .5 - - 1 / (2 + 22’888.32 CHF) * 4 - 6".EvaluateDecimal(null, new CultureInfo("de-CH"));

"ln(1/-0.5 + √(1/(0.5^2) + 1))".Evaluate(new ScientificMathContext());

"ln(1/-0,5 + √(1/(0,5^2) + 1))".Evaluate(new ScientificMathContext(), new CultureInfo("fr"));

"ln(1/-0.5 + √(1/(0.5^2) + 1))".EvaluateDecimal(new DecimalScientificMathContext());

"ln(1/-0,5 + √(1/(0,5^2) + 1))".EvaluateDecimal(new DecimalScientificMathContext(), new CultureInfo("fr"));

"4 % 3".Evaluate(new ProgrammingMathContext());

"4 mod 3".EvaluateDecimal(new DecimalScientificMathContext());

"4 <> 4 OR 5.4 = 5.4 AND NOT 0 < 1 XOR 1.0 - 1.95 * 2 >= -12.9 + 0.1 / 0.01".EvaluateBoolean(new ProgrammingMathContext());

"¬⊥∧⊤∨¬⊤⇒¬⊤".EvaluateBoolean(new ScientificMathContext());

Examples of using an instance of the MathExpression class:

new MathExpression("22888.32 * 30 / 323.34 / .5 - -1 / (2 + 22888.32) * 4 - 6").Evaluate();

new MathExpression("22888.32 * 30 / 323.34 / .5 - -1 / (2 + 22888.32) * 4 - 6").EvaluateDecimal();

new MathExpression("$22,888.32 * 30 / 323.34 / .5 - - 1 / (2 + $22,888.32) * 4 - 6", null, new CultureInfo("en-US")).Evaluate();

new MathExpression("22’888.32 CHF * 30 / 323.34 / .5 - - 1 / (2 + 22’888.32 CHF) * 4 - 6", null, new CultureInfo("de-CH")).EvaluateDecimal();

new MathExpression("ln(1/-0.5 + √(1/(0.5^2) + 1))", new ScientificMathContext()).Evaluate();

new MathExpression("ln(1/-0,5 + √(1/(0,5^2) + 1))", new ScientificMathContext(), new CultureInfo("fr")).Evaluate();

new MathExpression("ln(1/-0.5 + √(1/(0.5^2) + 1))", new DecimalScientificMathContext()).EvaluateDecimal();

new MathExpression("ln(1/-0,5 + √(1/(0,5^2) + 1))", new DecimalScientificMathContext(), new CultureInfo("fr")).EvaluateDecimal();

new MathExpression("4 % 3", new ProgrammingMathContext()).Evaluate();

new MathExpression("4 mod 3", new DecimalScientificMathContext()).EvaluateDecimal();

new MathExpression("4 <> 4 OR 5.4 = 5.4 AND NOT 0 < 1 XOR 1.0 - 1.95 * 2 >= -12.9 + 0.1 / 0.01", new ProgrammingMathContext()).EvaluateBoolean();

new MathExpression("¬⊥∧⊤∨¬⊤⇒¬⊤", new ScientificMathContext()).EvaluateBoolean();

Examples of passing custom variables and functions as parameters:

var x1 = 0.5;
var x2 = -0.5;
var sqrt = Math.Sqrt;
Func<double, double> ln = Math.Log;

var value1 = "ln(1/-x1 + sqrt(1/(x2*x2) + 1))"
    .Evaluate(new { x1, x2, sqrt, ln });

var parameters = new MathParameters();
parameters.BindVariable(0.5, "x1");
parameters.BindVariable(-0.5, "x2");
parameters.BindFunction(Math.Sqrt);
parameters.BindFunction(d => Math.Log(d), "ln");

var value2 = "ln(1/-x1 + Math.Sqrt(1/(x2*x2) + 1))"
    .Evaluate(parameters);

Example of using custom context:

var context = new MathContext();
context.BindFunction(Math.Sqrt);
context.BindFunction(d => Math.Log(d), "ln");

"ln(1/-x1 + Math.Sqrt(1/(x2*x2) + 1))"
    .Evaluate(new { x1 = 0.5, x2 = -0.5 }, context);

Examples of compilation:

Func<decimal> fn1 = "22’888.32 CHF * 30 / 323.34 / .5 - - 1 / (2 + 22’888.32 CHF) * 4 - 6"
    .CompileDecimal(null, new CultureInfo("de-CH"));

var value1 = fn1();

var fn2 = "ln(1/x1 + √(1/(x2*x2) + 1))"
    .Compile(new { x1 = 0.0, x2 = 0.0 }, new ScientificMathContext());

var value2 = fn2(new { x1 = -0.5, x2 = 0.5 });

Supported math functions, operators, and constants

When no mathematical context is specified:

Programming Math Context (using ProgrammingMathContext class):

Scientific Math Context (using ScientificMathContext class):

How to evaluate C# math string expression

DotNetStandartMathContext is the .NET Standart 2.1 programming math context supports all constants and functions provided by the System.Math class, and supports equlity, comparision, logical boolean operators.

Example of evaluating C# expression:

"-2 * Math.Log(1/0.5f + Math.Sqrt(1/Math.Pow(0.5d, 2) + 1L))".Evaluate(new DotNetStandartMathContext());

NOTE: More math functions could be added to the math expression evaluator based on user needs.

Contributing

Contributions are welcome! Please fork the repository and submit pull requests for any enhancements or bug fixes. If you enjoy my work and find it valuable, please consider becoming my sponsor on GitHub. Your support will enable me to share more open-source code. Together, we can make a positive impact in the developer community!

License

This project is licensed under the Apache License, Version 2.0 - see the LICENSE file for details.

Contact

If you have any questions or suggestions, feel free to open an issue or contact me directly.