Seq

1 min read

Import: import system.collections;

Read the usage guide for examples and common tasks. This reference lists the public declarations for this part of the library. See Reading API signatures for parameter and result notation.

Seq

A repeatable query sequence whose filters and transformations run during traversal.

public class Seq<T>: Iterable<T>

iterator

Creates an independent cursor. Closing it also closes every upstream cursor.

public borrow fun iterator(): Iterator<T>

filter

Lazily keeps the elements for which p returns true.

public fun filter(borrow p: fun(T): bool): Seq<T>

take

Lazily keeps at most n elements; nonpositive counts produce an empty sequence.

public fun take(n: int): Seq<T>

skip

Lazily skips the first n elements; nonpositive counts skip nothing.

public fun skip(n: int): Seq<T>

to_list

Collects the surviving elements into a fresh list.

public fun to_list(): List<T>

count

Counts the surviving elements without building a list.

public fun count(): int

distinct

Lazily removes duplicates while preserving first-seen order.

public fun distinct(): Seq<T>

sort_by

Immediately collects and sorts the sequence with cmp.

public fun sort_by(borrow cmp: fun(T, T): int): Seq<T>

flat_map

Lazily maps each element to a list and visits each result in order.

public fun flat_map<U>(borrow f: fun(T): List<U>): Seq<U>

map

Lazily transforms each element through f.

public fun map<U>(borrow f: fun(T): U): Seq<U>

reduce

Combines elements in order, starting with init; returns init when empty.

public fun reduce<A>(init: A, borrow f: fun(A, T): A): A

collect_set

Collects the elements into a new set, removing duplicates.

public fun collect_set(): Set<T>

min

Returns the smallest element by compare, or None when empty.

public fun min(): Option<T> where T: Comparable<T>

max

Returns the largest element by compare, or None when empty.

public fun max(): Option<T> where T: Comparable<T>