functionx #

A powerful equation parser and solver for Dart — f(x) for your code.

Features #

• 🧮 Expression Parsing - Support for both explicit and implicit multiplication
• 📊 Variable Extraction - Intelligently extract variables while filtering constants
• 🔢 Expression Evaluation - Multi-mode evaluation (Real, Complex, and Mixed)
• ⚡ Equation Solving - High-precision algebraic and numerical solvers
• 📈 Symbolic Calculus - Fast differentiation and integration
• 🔬 Auto-resolve Constants - Automatic identification of symbols like $c$, $h$, and $k_B$
• 🇬🇷 LaTeX Support - Seamless parsing of Greek letters and complex subscripts

Installation #

Add to your pubspec.yaml:

dependencies:
  functionx: ^1.1.0

Quick Start #

import 'package:functionx/functionx.dart';

void main() {
  // Extract variables from an equation
  final vars = ExpressionParser.extractVariables('y = m*x + b');
  print(vars); // ['b', 'm', 'x', 'y']

  // Evaluate an expression
  final result = Evaluator.evaluate('x^2 + 2*x + 1', {'x': 3});
  print(result); // 16.0

  // Solve an equation
  final solution = Solver.solve(
    'F = m*a',
    {'F': 10, 'm': 2},
    solveFor: 'a',
  );
  print(solution.value); // 5.0

  // Use physical constants
  final c = Constants.speedOfLight;
  print('${c.name}: ${c.value} ${c.unit}'); // Speed of Light: 299792458 m/s

  // Symbolic differentiation
  final derivative = Cas.differentiate('x^2', 'x');
  print(derivative); // '2.0 * x'
}

Expression Syntax #

This parser is designed to be ergonomic, supporting both explicit and implicit (shorthand) notation:

Supported Operators #

Supported Functions #

Mathematical Constants #

Reserved Words & Aliases #

To avoid conflicts with physical constants (like $c$ for the speed of light vs $c$ for a variable), functionx uses a set of reserved ergonomic aliases. These words are protected and will be pre-filled or handled as functions/constants:

• Functions: sin, cos, tan, asin, acos, atan, sqrt, abs, log, ln, exp, pow
• Math Constants: PI, EN, INF, IN (Uppercase required to avoid variable collisions)
• Ergonomic Aliases: SOL, GC, PC, BC, EC, RG, SG, EN, EM/ER, SM/SR, CC, ME, MP, MN, BR, FSC, SBC, LY, RYD, BM, NM, PEM, FC, MFQ, CQ, JC, VK, WIE, C1, C2 (Case-insensitive)

Note: functionx is smart enough to recognize both symbols (like π, ∞, h) and their designated keys. It automatically filters these during variable extraction so they don't appear as "unknowns" in your UI.

API Reference #

ExpressionParser #

// Parse expression or equation
final result = ExpressionParser.parse('y = m*x + b');
print(result.isEquation); // true

// Extract variables
final vars = ExpressionParser.extractVariables('F = m*a');
print(vars); // ['F', 'a', 'm']

Evaluator #

// Evaluate with variables
final result = Evaluator.evaluate('x^2 + y', {'x': 3, 'y': 5});
print(result); // 14.0

// Evaluate numeric expression (no variables)
final result = Evaluator.evaluateNumeric('2 + 3 * 4');
print(result); // 14.0

Solver #

// Solve for unknown variable
final result = Solver.solve(
  '2*x + 5 = 11',
  {'x': null},
);
print(result.value); // 3.0
print(result.steps); // ['...solution steps...']

// Solve physics equation
final result = Solver.solve(
  'F = m*a',
  {'F': 10, 'm': 2},
  solveFor: 'a',
);
print(result.value); // 5.0

Cas (Computer Algebra System) #

// Differentiation
final deriv = Cas.differentiate('x^3', 'x');
print(deriv); // '3.0 * x ^ 2.0'

// Integration
final integral = Cas.integrate('x', 'x');
print(integral); // '0.5*x^2'

// Simplification
final simplified = Cas.simplify('x + x');
print(simplified); // '2.0 * x'

Constants #

A comprehensive collection of physical and mathematical constants.

// Access by property
final c = Constants.speedOfLight;
print(c.value);  // 299792458
print(c.symbol); // c
print(c.unit);   // m/s
print(c.name);   // Speed of Light

// Get by key
final g = Constants.get('GC');
print(g?.value); // 6.6743e-11

// List all constants in a category
final fundamental = Constants.byCategory('fundamental');

// Search constants
final results = Constants.search('mass');

Available Categories

Common Constants

License #

MIT License - see LICENSE for details.