Method: Enumerator::Lazy#enum_for

Defined in:
enumerator.c

#to_enum(method = :each, *args) ⇒ Object #enum_for(method = :each, *args) ⇒ Object #to_enum(method = :each, *args) {|*args| ... } ⇒ Object #enum_for(method = :each, *args) {|*args| ... } ⇒ Object

Similar to Object#to_enum, except it returns a lazy enumerator. This makes it easy to define Enumerable methods that will naturally remain lazy if called from a lazy enumerator.

For example, continuing from the example in Object#to_enum:

# See Object#to_enum for the definition of repeat
r = 1..Float::INFINITY
r.repeat(2).first(5) # => [1, 1, 2, 2, 3]
r.repeat(2).class # => Enumerator
r.repeat(2).map{|n| n ** 2}.first(5) # => endless loop!
# works naturally on lazy enumerator:
r.lazy.repeat(2).class # => Enumerator::Lazy
r.lazy.repeat(2).map{|n| n ** 2}.first(5) # => [1, 1, 4, 4, 9]

Overloads:

  • #to_enum(method = :each, *args) {|*args| ... } ⇒ Object

    Yields:

    • (*args)
  • #enum_for(method = :each, *args) {|*args| ... } ⇒ Object

    Yields:

    • (*args) 


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# File 'enumerator.c', line 1974

static VALUE
lazy_to_enum(int argc, VALUE *argv, VALUE self)
{
    VALUE lazy, meth = sym_each, super_meth;

    if (argc > 0) {
        --argc;
        meth = *argv++;
    }
    if (RTEST((super_meth = rb_hash_aref(lazy_use_super_method, meth)))) {
        meth = super_meth;
    }
    lazy = lazy_to_enum_i(self, meth, argc, argv, 0, rb_keyword_given_p());
    if (rb_block_given_p()) {
        RB_OBJ_WRITE(lazy, &enumerator_ptr(lazy)->size, rb_block_proc());
    }
    return lazy;
}