Thorbjørn Lindeijer
8f54dc5f76
Adds a new `any` method to the Sequence class that tests whether any element in the sequence passes the given predicate function, returning true on the first match or false if none match. Includes documentation, core library source update, and three new test files covering basic functionality, non-boolean return values, and non-function argument error handling.
2.4 KiB
^title Sequence Class ^category core
An abstract base class for any iterable object. Any class that implements the core iterator protocol can extend this to get a number of helpful methods.
all(predicate)
Tests whether all the elements in the sequence pass the predicate.
Iterates over the sequence, passing each element to the function predicate.
If its return value evaluates to false, stops iterating and returns false.
Otherwise, returns true.
:::dart
[1, 2, 3].all {|n| n > 2} // False.
[1, 2, 3].all {|n| n < 4} // True.
any(predicate)
Tests whether any element in the sequence passes the predicate.
Iterates over the sequence, passing each element to the function predicate.
If its return value evaluates to true, stops iterating and returns true.
Otherwise, returns false.
:::dart
[1, 2, 3].any {|n| n < 1} // False.
[1, 2, 3].any {|n| n > 2} // True.
join(sep)
Returns a string representation of the list. The string representations of the
elements in the list is concatenated with intervening occurrences of sep.
It is a runtime error if sep is not a string.
join
Calls join with the empty string as the separator.
map(transformation)
Creates a new list by applying transformation to each element in the
sequence.
Iterates over the sequence, passing each element to the function
transformation. Generates a new list from the result of each of those calls.
:::dart
[1, 2, 3].map {|n| n * 2} // [2, 4, 6].
reduce(function)
Reduces the sequence down to a single value. function is a function that takes two arguments, the accumulator and sequence item and returns the new accumulator value. The accumulator is initialized from the first item in the sequence. Then, the function is invoked on each remaining item in the sequence, iteratively updating the accumulator.
It is a runtime error to call this on an empty sequence.
reduce(seed, function)
Similar to above, but uses seed for the initial value of the accumulator. If the sequence is empty, returns seed.
where(predicate)
Produces a new list containing only the elements in the sequence that pass the
predicate.
Iterates over the sequence, passing each element to the function predicate.
If it returns true, adds the element to the result list.
(1..10).where {|n| n % 2 == 1} // [1, 3, 5, 7, 9].