function_tree 0.2.5

A library for parsing and evaluating numerical functions built from strings.

example/example.dart

import 'package:function_tree/function_tree.dart';
import 'dart:math' show pi;

void main() {
  // FunctionOfX...
  var f = FunctionOfX("abs(sin(x)) + cos(abs(x)) / 2"),
      n = 50,
      xs = List.generate(n + 1, (i) => -pi + i * 2 * pi / n),
      ys = xs.map(f);

  // A rough sketch of the graph of this function over [-π, π].
  ys.map((y) => "|${" " * (y * 50).round()}+").forEach(print);

  // FunctionTree
  var tree = FunctionTree(
      fromExpression: "abs(sin(a) + cos(b))", withVariableNames: ["a", "b"]);

  print("+${"-" * xs.length}+");
  for (var a in xs) {
    print("|${xs.map((b) {
      var value = tree({"a": a, "b": b});
      if (value < 0.5) return " ";
      if (value < 1) return ":";
      if (value < 1.5) return "o";
      return "*";
    }).join()}|");
  }
  print("+${"-" * xs.length}+");
}