contrast2 0.2.0+1

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  • Example
  • Installing
  • Versions
  • new55

contrast2

Build Status

Utilities for comparing (and contrast2ing) dart values:

  • Comparator combinators (by/compound/reverse/lexicographic/nullsFirst/nullsLast)
  • Comparison operator mixin (Quantity)(<, <=, ==, >, >=)
  • Find extrema of Comparables and Iterables (min/max/minOf/maxOf)
  • Test and obtain clamped comparables (clamp/between)
  • Test and obtain sorted iterables (sorted/isOrdered/isStrictlyOrdered)

#Example


import 'package:contrast2/contrast2.dart';
import 'dart:math' as math;

main() {
  
  // Easily define comparison operators (see Point class below).
  assert(Point.ZERO < Point.UNIT);
  assert(Point.UNIT >= Point.ZERO);
  assert(Point.ZERO == new Point(0, 0));

  // Find extrema of arbitrary comparables.
  // (dart:math's min/max only work with numbers)
  assert(min(Point.ZERO, Point.UNIT) == Point.ZERO);
  assert(max(Point.ZERO, Point.UNIT) == Point.UNIT);
  assert(clamp(new Point(1, 2), Point.ZERO, Point.UNIT) == Point.UNIT);
  assert(between(new Point(0.5, 0.5), Point.ZERO, Point.UNIT));
  
  // Find extrema of iterables.
  var points = [Point.UNIT, new Point(1, 2), Point.ZERO, new Point(0, 1)];
  assert(minOf(points) == Point.ZERO);
  assert(maxOf(points) == new Point(1, 2));
  
  // Sort into a new List easily ( vs. iterable.toList()..sort() ).
  var sortedPoints = sorted(points);
  
  // Check ordering of iterables.
  assert(isOrdered(sortedPoints));
  assert(isStrictlyOrdered(sortedPoints));

  // Define comparators using combinator helpers...
  
  // By key function
  var byMagnitude = by((point) => point.magnitude);
  assert(max(Point.ZERO, new Point(-1, -1), 
      compare: byMagnitude) == new Point(-1, -1));
  
  // Compound
  assert(max(Point.ZERO, new Point(-1, -1), 
      compare: compound([byMagnitude, Comparable.compare])) == new Point(-1, -1));
  
  // Reversed
  assert(max(Point.ZERO, Point.UNIT, compare: reverse()) == Point.ZERO);

  // Lexicographic
  assert(min([Point.ZERO, Point.UNIT], [Point.ZERO, new Point(2, 2)], 
      compare: lexicographic()).last == Point.UNIT);
  
  // Null safe
  var maybePoints = [Point.UNIT, null, Point.ZERO, null];
  assert(sorted(maybePoints, compare: nullsFirst()).first == null);
  assert(sorted(maybePoints, compare: nullsLast()).last == null);
}

// Mixin `Comparable`-based comparison operators with `Quantity`.
class Point extends Object with Quantity<Point> {
  
  static Point ZERO = new Point(0, 0);
  static Point UNIT = new Point(1, 1);
  
  final num x, y;
  
  num get magnitude => math.sqrt(x*x + y*y);
  
  Point(this.x, this.y);
  
  // Use comparator combinators`compound` and `by`.
  static final _comparator = compound([by((p) => p.x), by((p) => p.y)]);
  
  int compareTo(Point other) => _comparator(this, other);
  
  toString() => '($x, $y)';
}

example/example.dart

import 'package:contrast2/contrast2.dart';
import 'dart:math' as math;

main() {
  // Easily define comparison operators (see Point class below).
  assert(Point.ZERO < Point.UNIT);
  assert(Point.UNIT >= Point.ZERO);
  assert(Point.ZERO == new Point(0, 0));

  // Find extrema of arbitrary comparables.
  // (dart:math's min/max only work with numbers)
  assert(min(Point.ZERO, Point.UNIT) == Point.ZERO);
  assert(max(Point.ZERO, Point.UNIT) == Point.UNIT);
  assert(clamp(new Point(1, 2), Point.ZERO, Point.UNIT) == Point.UNIT);
  assert(between(new Point(0.5, 0.5), Point.ZERO, Point.UNIT));

  // Find extrema of iterables.
  var points = [Point.UNIT, new Point(1, 2), Point.ZERO, new Point(0, 1)];
  assert(minOf(points) == Point.ZERO);
  assert(maxOf(points) == new Point(1, 2));

  // Sort into a new List easily ( vs. iterable.toList()..sort() ).
  var sortedPoints = sorted(points);

  // Check ordering of iterables.
  assert(isOrdered(sortedPoints));
  assert(isStrictlyOrdered(sortedPoints));

  // Define comparators using combinator helpers...

  // By key function
  var byMagnitude = by((point) => point.magnitude);
  assert(max(Point.ZERO, new Point(-1, -1), compare: byMagnitude) ==
      new Point(-1, -1));

  // Compound
  assert(max(Point.ZERO, new Point(-1, -1),
          compare: compound([byMagnitude, Comparable.compare])) ==
      new Point(-1, -1));

  // Reversed
  assert(max(Point.ZERO, Point.UNIT, compare: reverse()) == Point.ZERO);

  // Lexicographic
  // assert(min([Point.ZERO, Point.UNIT], [Point.ZERO, new Point(2, 2)],
  //     compare: lexicographic()).last == Point.UNIT);

  // Null safe
  var maybePoints = [Point.UNIT, null, Point.ZERO, null];
  assert(sorted(maybePoints, compare: nullsFirst()).first == null);
  assert(sorted(maybePoints, compare: nullsLast()).last == null);
}

// Mixin `Comparable`-based comparison operators with `Quantity`.
class Point extends Object with Quantity<Point> {
  static Point ZERO = new Point(0, 0);
  static Point UNIT = new Point(1, 1);

  final num x, y;

  num get magnitude => math.sqrt(x * x + y * y);

  Point(this.x, this.y);

  // Use comparator combinators`compound` and `by`.
  static final _comparator = compound([by((p) => p.x), by((p) => p.y)]);

  int compareTo(Point other) => _comparator(this, other);

  toString() => '($x, $y)';
}

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:


dependencies:
  contrast2: ^0.2.0+1

2. Install it

You can install packages from the command line:

with pub:


$ pub get

with Flutter:


$ flutter packages get

Alternatively, your editor might support pub get or flutter packages get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:contrast2/contrast2.dart';
  
Version Uploaded Documentation Archive
0.2.0+1 Sep 3, 2018 Go to the documentation of contrast2 0.2.0+1 Download contrast2 0.2.0+1 archive
0.2.0 Sep 3, 2018 Go to the documentation of contrast2 0.2.0 Download contrast2 0.2.0 archive
Popularity:
Describes how popular the package is relative to other packages. [more]
18
Health:
Code health derived from static analysis. [more]
100
Maintenance:
Reflects how tidy and up-to-date the package is. [more]
80
Overall:
Weighted score of the above. [more]
55
Learn more about scoring.

We analyzed this package on Sep 18, 2018, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.0.0
  • pana: 0.12.3

Platforms

Detected platforms: Flutter, web, other

No platform restriction found in primary library package:contrast2/contrast2.dart.

Issues and suggestions

Maintain CHANGELOG.md.

Changelog entries help clients to follow the progress in your code.

Format lib/contrast2.dart.

Run dartfmt to format lib/contrast2.dart.

Format lib/src/ordered.dart.

Run dartfmt to format lib/src/ordered.dart.

Fix lib/src/quantity.dart.

Analysis of lib/src/quantity.dart reported 1 hint:

line 10 col 17: Always override hashCode if overriding ==.

Dependencies

Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.0.0-dev.60.2 <3.0.0
Dev dependencies
quiver ^2.0.0
test 1.3.0