eval_ex

A Dart port of https://github.com/uklimaschewski/EvalEx.
EvalEx supports mathematical and boolean expression evaluation, using arbitrary precision. EvalEx supports functions, variables, and operators and additionally makes it very easy to add your own custom functions or operators.

EvalEx uses decimal to support arbitrary precision arithmetic.
View package on pub.dev.

Basic example

void main() {
  Expression exp = Expression("2 ^ 4 + 8");
  print(exp.eval().toString()); // 24

  // With a variable
  exp = Expression("a ^ b + c");
  // Variables may contain alphanumeric characters, and "_". This can be changed
  // by using setVariableCharacters(..) and setFirstVariableCharacters(..) (what chars variable are allowed to start with).
  exp.setStringVariable("a", "2");
  exp.setStringVariable("b", "4");
  exp.setStringVariable("c", "8");
  print(exp.eval().toString()); // 24

  // With a function
  exp = Expression("MAX(-7,8)");
  print(exp.eval().toString()); // 8

  // Boolean logic
  exp = Expression("1>0 && 5 == 5");
  print(exp.eval().toString()); // 1

  exp = Expression("1>0 && 5 == 4");
  print(exp.eval().toString()); // 0

  // Adding a custom operator

  Expression exp = Expression('23 custom_operator 20');
  exp.addOperator(OperatorImpl("custom_operator", Expression.operatorPrecedenceAdditive, true,
      fEval: (v1, v2) {
    return v1 + v2;
  }));
  print(exp.eval()); // 43

  // Adding a custom function

  exp = Expression('cube(4) + 2');
  exp.addFunc(FunctionImpl("cube", 1, booleanFunction: false, fEval: (params) {
   num n = pow(params.first.toDouble(),3);
   return Decimal.parse(n.toString());
  }));
  print(exp.eval()) // 66

  // Custom function for returning the difference between two numbers

  exp = Expression('difference(4,2)');
  exp.addFunc(FunctionImpl("difference", 2, booleanFunction: false, fEval: (params) {
   return (params[0]-params[1]).abs();
  }));
  print(exp.eval()); // 2
}

Built-in functions and operators

Operators

Trigonometry

Standard, degrees

Inverse arc functions, degrees

Standard, radians

Inverse arc functions, radians

Standard, gradians

Inverse arc functions, gradians

Standard, hyperbolic

Inverse arc, hyperbolic

Converters

More

Adding custom functions, operators, and variables

You can also define your custom functions, operators, and variables in built_ins.dart

Differences from https://github.com/uklimaschewski/EvalEx.

• The SQRT function is currently limited to 64-bit precision
• Built in operators/functions/variables are instead defined in built_ins.dart