Philiprehberger.ExpressionEvaluator

Safe mathematical expression parser and evaluator with variables, custom functions, and operator precedence.

Installation

dotnet add package Philiprehberger.ExpressionEvaluator

Usage

using Philiprehberger.ExpressionEvaluator;

double result = Evaluator.Eval("2 + 3 * 4");
// result = 14

Simple Evaluation

using Philiprehberger.ExpressionEvaluator;

Evaluator.Eval("10 / 2 + 1");   // 6
Evaluator.Eval("2 ^ 10");        // 1024
Evaluator.Eval("10 % 3");        // 1
Evaluator.Eval("-5 + 3");        // -2

Variables

using Philiprehberger.ExpressionEvaluator;

var variables = new Dictionary<string, double>
{
    ["x"] = 3,
    ["y"] = 4
};

double result = Evaluator.Eval("sqrt(x^2 + y^2)", variables);
// result = 5

Comparison Operators

using Philiprehberger.ExpressionEvaluator;

Evaluator.Eval("3 > 2");    // 1 (true)
Evaluator.Eval("3 < 2");    // 0 (false)
Evaluator.Eval("5 >= 5");   // 1
Evaluator.Eval("4 <= 3");   // 0
Evaluator.Eval("5 == 5");   // 1
Evaluator.Eval("5 != 3");   // 1

Conditional Expressions

using Philiprehberger.ExpressionEvaluator;

var vars = new Dictionary<string, double> { ["x"] = -5 };

Evaluator.Eval("x > 0 ? x : -x", vars);   // 5 (absolute value via ternary)
Evaluator.Eval("1 > 2 ? 100 : 200");       // 200

Custom Functions

using Philiprehberger.ExpressionEvaluator;

var evaluator = new Evaluator();
evaluator.RegisterFunction("clamp", 3, args =>
    Math.Max(args[1], Math.Min(args[2], args[0])));

evaluator.Evaluate("clamp(15, 0, 10)");  // 10
evaluator.Evaluate("clamp(-5, 0, 10)");  // 0

Built-in Functions

using Philiprehberger.ExpressionEvaluator;

Evaluator.Eval("abs(-42)");           // 42
Evaluator.Eval("min(10, 20)");        // 10
Evaluator.Eval("max(10, 20)");        // 20
Evaluator.Eval("round(3.7)");         // 4
Evaluator.Eval("ceil(2.1)");          // 3
Evaluator.Eval("floor(2.9)");         // 2
Evaluator.Eval("sin(pi / 2)");        // 1
Evaluator.Eval("log(e)");             // 1
Evaluator.Eval("pow(2, 10)");         // 1024
Evaluator.Eval("log10(100)");         // 2

Compiled Expressions

using Philiprehberger.ExpressionEvaluator;

var formula = Evaluator.CompileStatic("x^2 + 2*x + 1");

double r1 = formula(new Dictionary<string, double> { ["x"] = 3 });  // 16
double r2 = formula(new Dictionary<string, double> { ["x"] = 5 });  // 36

API

Evaluator (static methods)

Method	Description
Eval(string expression, IDictionary<string, double>? variables = null)	Parses and evaluates an expression, returning the result
CompileStatic(string expression)	Compiles an expression into a reusable delegate

Evaluator (instance methods)

Method	Description
RegisterFunction(string name, Func<double[], double> function)	Registers a custom function by name
RegisterFunction(string name, int arity, Func<double[], double> function)	Registers a custom function with arity validation
Evaluate(string expression, IDictionary<string, double>? variables = null)	Evaluates an expression with access to registered custom functions
Compile(string expression)	Compiles an expression with access to registered custom functions

Comparison Operators

Operator	Description
>	Greater than (returns 1.0 or 0.0)
<	Less than
>=	Greater than or equal
<=	Less than or equal
==	Equal
!=	Not equal

Conditional Expression

Syntax	Description
condition ? trueExpr : falseExpr	Evaluates trueExpr if condition is non-zero, falseExpr otherwise

Built-in Functions

Function	Description
abs(x)	Absolute value
min(x, y)	Minimum of two values
max(x, y)	Maximum of two values
sqrt(x)	Square root
round(x)	Round to nearest integer
ceil(x)	Round up to nearest integer
floor(x)	Round down to nearest integer
sin(x)	Sine (radians)
cos(x)	Cosine (radians)
tan(x)	Tangent (radians)
asin(x)	Inverse sine
acos(x)	Inverse cosine
atan(x)	Inverse tangent
atan2(y, x)	Two-argument inverse tangent
log(x)	Natural logarithm
log10(x)	Base-10 logarithm
exp(x)	Exponential (e^x)
pow(x, y)	Power (x^y)
sign(x)	Sign (-1, 0, or 1)
truncate(x)	Truncate toward zero
pi	Constant 3.14159...
e	Constant 2.71828...

Development

dotnet build src/Philiprehberger.ExpressionEvaluator.csproj --configuration Release

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License

MIT