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instance method
Enumerator::Lazy#enum_for
(::Symbol method, *untyped, **untyped) ?{ (?) -> ::Integer } -> ::Enumerator[untyped, untyped]
() ?{ () -> ::Integer } -> ::Enumerator[E, self]
lzy.enum_for(method = :each, *args) → lazy_enum
lzy.enum_for(method = :each, *args) {|*args| block } → lazy_enum
enumerator.c
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static VALUE
lazy_to_enum(int argc, VALUE *argv, VALUE self)
{
VALUE lazy, meth = sym_each, super_meth;
if (argc > 0) {
--argc;
meth = rb_to_symbol(*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;
}
Alias of #to_enum
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:
Example
# 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]