Guides

These guides describe the design and intention behind the APIs included in the Algorithms library. For further reading, see the announcement on swift.org and the official documentation.

Contents

Combinations / permutations

• combinations(ofCount:): Combinations of particular sizes of the elements in a collection.
• permutations(ofCount:): Permutations of a particular size of the elements in a collection, or of the full collection.
• uniquePermutations(ofCount:): Permutations of a collection's elements, skipping any duplicate permutations.

Mutating algorithms

• rotate(toStartAt:), rotate(subrange:toStartAt:): In-place rotation of elements.
• stablePartition(by:), stablePartition(subrange:by:): A partition that preserves the relative order of the resulting prefix and suffix.

Combining collections

• chain(_:_:): Concatenates two collections with the same element type.
• cycled(), cycled(times:): Repeats the elements of a collection forever or a set number of times.
• joined(by:): Concatenate sequences of sequences, using an element or sequence as a separator, or using a closure to generate each separator.
• product(_:_:): Iterates over all the pairs of two collections; equivalent to nested for-in loops.

Subsetting operations

• compacted(): Drops the nils from a sequence or collection, unwrapping the remaining elements.
• partitioned(by:): Returns the elements in a sequence or collection that do and do not match a given predicate.
• randomSample(count:), randomSample(count:using:): Randomly selects a specific number of elements from a collection.
• randomStableSample(count:), randomStableSample(count:using:): Randomly selects a specific number of elements from a collection, preserving their original relative order.
• striding(by:): Returns every nth element of a collection.
• suffix(while:): Returns the suffix of a collection where all element pass a given predicate.
• trimmingPrefix(while:), trimmingSuffix(while), trimming(while:): Returns a slice by trimming elements from a collection's start, end, or both. The mutating trim... methods trim a collection in place.
• uniqued(), uniqued(on:): The unique elements of a collection, preserving their order.
• minAndMax(), minAndMax(by:): Returns the smallest and largest elements of a sequence.

Partial sorting

• min(count:), max(count:), min(count:sortedBy:), max(count:sortedBy:): Returns the smallest or largest elements of a collection, sorted by a predicate.

Other useful operations

• adjacentPairs(): Lazily iterates over tuples of adjacent elements.
• chunked(by:), chunked(on:), chunks(ofCount:): Eager and lazy operations that break a collection into chunks based on either a binary predicate or when the result of a projection changes or chunks of a given count.
• firstNonNil(_:): Returns the first non-nil result from transforming a sequence's elements.
• grouped(by:): Group up elements using the given closure, returning a Dictionary of those groups, keyed by the results of the closure.
• indexed(): Iterate over tuples of a collection's indices and elements.
• interspersed(with:): Place a value between every two elements of a sequence.
• keyed(by:), keyed(by:resolvingConflictsBy:): Returns a Dictionary that associates elements of a sequence with the keys returned by the given closure.
• partitioningIndex(where:): Returns the starting index of the partition of a collection that matches a predicate.
• reductions(_:), reductions(_:_:): Returns all the intermediate states of reducing the elements of a sequence or collection.
• split(maxSplits:omittingEmptySubsequences:whereSeparator), split(separator:maxSplits:omittingEmptySubsequences): Lazy versions of the Standard Library's eager operations that split sequences and collections into subsequences separated by the specified separator element.
• windows(ofCount:): Breaks a collection into overlapping subsequences where elements are slices from the original collection.