class method
Enumerator::Lazy.new
[out Elem, out Return = void] (?::Integer arg0) { (::Enumerator::Yielder arg0) -> Return } -> ::Enumerator::Lazy[Elem, Return]
Lazy.new(obj, size=nil) { |yielder, *values| block }
enumerator.c
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static VALUE
lazy_initialize(int argc, VALUE *argv, VALUE self)
{
VALUE obj, size = Qnil;
VALUE generator;
rb_check_arity(argc, 1, 2);
LAZY_NEED_BLOCK(new);
obj = argv[0];
if (argc > 1) {
size = argv[1];
}
generator = generator_allocate(rb_cGenerator);
rb_block_call(generator, id_initialize, 0, 0, lazy_init_block_i, obj);
enumerator_init(self, generator, sym_each, 0, 0, 0, size, 0);
rb_ivar_set(self, id_receiver, obj);
return self;
}
Creates a new Lazy enumerator. When the enumerator is actually enumerated (e.g. by calling force), obj will be enumerated and each value passed to the given block. The block can yield values back using yielder. For example, to create a “filter+map” enumerator:
Example
def filter_map(sequence) Lazy.new(sequence) do |yielder, *values| result = yield *values yielder << result if result end end filter_map(1..Float::INFINITY) {|i| i*i if i.even?}.first(5) #=> [4, 16, 36, 64, 100]