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Let sumBy accept num/int/double #138

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Mar 27, 2021
Merged

Let sumBy accept num/int/double #138

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13 changes: 5 additions & 8 deletions lib/src/collection/kt_iterable.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -1291,21 +1291,18 @@ extension KtIterableExtensions<T> on KtIterable<T> {
}

/// Returns the sum of all values produced by [selector] function applied to each element in the collection.
int sumBy(int Function(T) selector) {
int sum = 0;
R sumBy<R extends num>(R Function(T) selector) {
var sum = R == double ? 0.0 : 0;
for (final element in iter) {
sum += selector(element);
}
return sum;
return sum as R;
}

/// Returns the sum of all values produced by [selector] function applied to each element in the collection.
@Deprecated("Use sumBy")
double sumByDouble(double Function(T) selector) {
double sum = 0.0;
for (final element in iter) {
sum += selector(element);
}
return sum;
return sumBy(selector);
}

/// Returns a list containing first [n] elements.
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17 changes: 15 additions & 2 deletions test/collection/iterable_extensions_test.dart
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Expand Up @@ -1614,13 +1614,26 @@ void testIterable(KtIterable<T> Function<T>() emptyIterable,
});

group("sumBy", () {
test("double", () {
test("int", () {
expect(iterableOf([1, 2, 3]).sumBy((i) => i * 2), 12);
});

test("factor 1.5", () {
test("double", () {
expect(iterableOf([1, 2, 3]).sumBy((i) => i * 1.5), 9.0);

// ignore: deprecated_member_use_from_same_package
expect(iterableOf([1, 2, 3]).sumByDouble((i) => i * 1.5), 9.0);
});

test("double as num", () {
const num factor = 1.5;
expect(iterableOf([1, 2, 3]).sumBy((i) => i * factor), 9.0);
});

test("double as num", () {
const num factor = 2;
expect(iterableOf([1, 2, 3]).sumBy((i) => i * factor), 12);
});
});

group("take", () {
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