math_parser 1.2.0

Process math expressions, convert them to machine-readable form, and calculate them.

Math Parser for Dart

Process math expressions, convert them to machine-readable form, and calculate them.

Math Tree

The library provides a family of MathNode classes, most of them have subnodes that are being calculated recursively.

There are such types of MathNode:

• MathFunction (and MathFunctionWithTwoArguments subclass)
• MathValue
• MathOperator

All the child classes names begin with the family they belong to.

Evaluation

You can evaluate a MathNode and its subnodes recursively by calling MathNode.calc(MathVariableValues values) and passing custom variable values.

Example: Calculate x + 3, where x = 5.

MathOperatorAddition(
    MathVariable('x'),
    const MathValue(3),
).calc(MathVariableValues.x(5));

Parsing String to MathNode

The library can parse general mathematical expressions strings and return them as a machine-readable MathNode using MathNodeExpression.fromString method.

• Set isMinusNegativeFunction to true to interpret minus operator as a sum of two values, right of which will be negative: X - Y turns to X + (-Y)
• Set isImplicitMultiplication to false to disable implicit multiplication

Parse priority:

1. Parentheses () []
2. Variables: e, pi (π) and custom ones. x is being interpreted as a var by default, but you can override this behavior with the variableNames parameter. You can rewrite e and pi by defining it in variableNames and mentioning it during the calc call. First character must be a letter, others - letters, digits, or underscore. Letters may be latin or Greek, both lower or capital case. You can't use built-in function names like sin, cos, etc. Variable names are case-sensitive
3. Functions (case-sensitive):
   • sin, cos, tan (tg), cot (ctg)
   • sqrt (√) (interpreted as power of 1/2), complex numbers not supported
   • ln (base=E), lg (base=2), log[base](x)
   • asin (arcsin), acos (arccos), atan (arctg), acot (arcctg)
4. Unary minus (-) at the beginning of a block
5. Power (x^y)
6. Implicit multiplication (two MathNodes put near without operator between)
7. Division (/) & Multiplication (*)
8. Subtraction (-) & Addition (+)

MathNode fromString(
    /// The expression to convert
    String expression, {

    /// Converts all X - Y to X + (-Y)
    bool isMinusNegativeFunction = false,

    /// Allows skipping the multiplication (*) operator
    bool isImplicitMultiplication = true,

    /// Expressions which should be marked as variables
    Set<String> variableNames = const {'x'},
  });

Example for parsing a string and evaluating it with x = 20 and y = 5:

final expression = MathNodeExpression.fromString(
  '(2x)^(e^3 + 4) + y',
).calc(
  MathVariableValues({'x': 20, 'y': 5}),
);

More complicated work with variables is shown off in example.

Other Features

Numerical methods for Definite Integrals

You can calculate a given node as a definite integral using the MathNodeDefiniteIntegral extension. All methods have the same interface:

num definiteIntegralByLeftRectangles(
    /// Precision
    int n,
    num lowerLimit,
    num upperLimit,
);