countE method
Returns the number of elements in the enumerable.
Optionally, a condition
can be specified. If so, the total count
will be the number of elements for which the condition
function
returned true
.
If the condition
parameter is omitted and the underlying collection extends
or implements EfficientLengthIterable
, the countE method will call the
length
property of the iterable as an O(1) operation. Otherwise, the
countE function will iterate over every element in the enumerable.
Implementation
int countE([Condition<T> condition]) {
if (condition == null) return this.length;
final iterator = this.iterator;
if (!iterator.moveNext()) return 0;
int count = 0;
do {
if (condition(iterator.current)) count++;
} while (iterator.moveNext());
return count;
}