instance method

Array#cycle

(?::int? n) { (Elem) -> void } -> nil

(?::int? n) -> ::Enumerator[Elem, nil]

cycle(count = nil) {|element| ... } → nil

cycle(count = nil) → new_enumerator

static VALUE
rb_ary_cycle(int argc, VALUE *argv, VALUE ary)
{
    long n, i;

    rb_check_arity(argc, 0, 1);

    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_cycle_size);
    if (argc == 0 || NIL_P(argv[0])) {
        n = -1;
    }
    else {
        n = NUM2LONG(argv[0]);
        if (n <= 0) return Qnil;
    }

    while (RARRAY_LEN(ary) > 0 && (n < 0 || 0 < n--)) {
        for (i=0; i<RARRAY_LEN(ary); i++) {
            rb_yield(RARRAY_AREF(ary, i));
        }
    }
    return Qnil;
}

With a block given, may call the block, depending on the value of argument count; count must be an integer-convertible object, or nil.

When count is positive, calls the block with each element, then does so repeatedly, until it has done so count times; returns nil:

Example

output = []
[0, 1].cycle(2) {|element| output.push(element) } # => nil
output # => [0, 1, 0, 1]

When count is zero or negative, does not call the block:

Example

[0, 1].cycle(0) {|element| fail 'Cannot happen' }  # => nil
[0, 1].cycle(-1) {|element| fail 'Cannot happen' } # => nil

When count is nil, cycles forever:

Example

# Prints 0 and 1 forever.
[0, 1].cycle {|element| puts element }
[0, 1].cycle(nil) {|element| puts element }

With no block given, returns a new Enumerator.

Related: see Methods for Iterating.

See also #count #delete #concat #delete_at also in 4.1 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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