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Add .toCoordinates() method to grid

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Calculates the 2-D array coordinates from the corresponding list index passed in. Relies on grid width to calculate coordinates. Does not check against grid size constraints.
This commit is contained in:
Marty Oehme 2018-08-30 09:52:00 +02:00
parent 6c3fcbe7b0
commit 5a72783d57
2 changed files with 32 additions and 2 deletions
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11
lib/src/Grid.dart
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@ -35,7 +35,7 @@ class Grid<E> extends DelegatingList<E> {
void set(int x, int y, E value) => setElement(x, y, value);
/// Calculate list index from coordinates.
/// Calculate list index from coordinates
///
/// Can be used to get the correct index from coordinates passed in.
/// Will only calculate the index, not take into consideration any grid size
@ -44,5 +44,12 @@ class Grid<E> extends DelegatingList<E> {
? throw RangeError("Coordinates for Grid Indexing must not be negative.")
: y * width + x;
Point<int> toCoords(int index) => Point<int>(index % width, index ~/ width);
/// Calculate coordinates from list index
///
/// Calculates the 2-D array coordinates from the corresponding list index
/// passed in. Relies on grid width to calculate coordinates. Does not check
/// against grid size constraints; use [set] for that (generally recommended).
Point<int> toCoordinates(int index) => (index < 0)
? throw RangeError("Index for Grid Coordinates must not be negative")
: Point<int>(index % width, index ~/ width);
}

23
test/src/grid_test.dart
View file

@ -1,3 +1,5 @@
import 'dart:math';
import 'package:rules_of_living/src/Grid.dart';
import 'package:test/test.dart';
@ -115,4 +117,25 @@ void main() {
expect(sut.get(2, 2), "ready.");
}, tags: const ["happy"]);
});
group("toCoords", () {
Grid sut;
setUp(() {
sut = Grid(3, 3);
});
test("throws RangeError on negative index argument", () {
expect(() => sut.toCoordinates(-1), throwsA(isRangeError));
}, tags: const ["bad"]);
test("calculates correct index for first element", () {
expect(sut.toCoordinates(0), equals(Point(0, 0)));
}, tags: const ["happy"]);
test("calculates correct index for last element", () {
expect(sut.toCoordinates(8), equals(Point(2, 2)));
}, tags: const ["happy"]);
test("calculates correct index for last element on first row", () {
expect(sut.toCoordinates(2), equals(Point(2, 0)));
}, tags: const ["happy"]);
test("calculates correct index for example element", () {
expect(sut.toCoordinates(6), equals(Point(0, 2)));
}, tags: const ["happy"]);
});
}