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  • enumerator.c
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Enumerator::Lazy

Public Class Methods

new(obj, size=nil) { |yielder, *values| ... } click to toggle source

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 method filter_map in both lazy and non-lazy fashions:

module Enumerable
  def filter_map(&block)
    map(&block).compact
  end
end

class Enumerator::Lazy
  def filter_map
    Lazy.new(self) do |yielder, *values|
      result = yield *values
      yielder << result if result
    end
  end
end

(1..Float::INFINITY).lazy.filter_map{|i| i*i if i.even?}.first(5)
    # => [4, 16, 36, 64, 100]
 
               static VALUE
lazy_initialize(int argc, VALUE *argv, VALUE self)
{
    VALUE obj, size = Qnil;
    VALUE generator;

    rb_check_arity(argc, 1, 2);
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy new without a block");
    }
    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);
    rb_ivar_set(self, id_receiver, obj);

    return self;
}
            

Public Instance Methods

chunk(*args) click to toggle source
 
               static VALUE
lazy_super(int argc, VALUE *argv, VALUE lazy)
{
    return enumerable_lazy(rb_call_super(argc, argv));
}
            
collect() click to toggle source
 
               static VALUE
lazy_map(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy map without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_map_func, 0),
                           Qnil, lazy_receiver_size);
}
            
flat_map { |obj| block } → a_lazy_enumerator click to toggle source

Returns a new lazy enumerator with the concatenated results of running block once for every element in lazy.

["foo", "bar"].lazy.flat_map {|i| i.each_char.lazy}.force
#=> ["f", "o", "o", "b", "a", "r"]

A value x returned by block is decomposed if either of the following conditions is true:

a) <i>x</i> responds to both each and force, which means that
   <i>x</i> is a lazy enumerator.
b) <i>x</i> is an array or responds to to_ary.

Otherwise, x is contained as-is in the return value.

[{a:1}, {b:2}].lazy.flat_map {|i| i}.force
#=> [{:a=>1}, {:b=>2}]
 
               static VALUE
lazy_flat_map(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy flat_map without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_flat_map_func, 0),
                           Qnil, 0);
}
            
drop(p1) click to toggle source
 
               static VALUE
lazy_drop(VALUE obj, VALUE n)
{
    long len = NUM2LONG(n);

    if (len < 0) {
        rb_raise(rb_eArgError, "attempt to drop negative size");
    }
    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_drop_func, n),
                           rb_ary_new3(1, n), lazy_drop_size);
}
            
drop_while() click to toggle source
 
               static VALUE
lazy_drop_while(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy drop_while without a block");
    }
    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_drop_while_func, 0),
                           Qnil, 0);
}
            
enum_for(method = :each, *args) → lazy_enum click to toggle source
enum_for(method = :each, *args){|*args| block} → lazy_enum

Similar to Kernel#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 Kernel#to_enum:

# See Kernel#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]
 
               static VALUE
lazy_to_enum(int argc, VALUE *argv, VALUE self)
{
    VALUE lazy, meth = sym_each;

    if (argc > 0) {
        --argc;
        meth = *argv++;
    }
    lazy = lazy_to_enum_i(self, meth, argc, argv, 0);
    if (rb_block_given_p()) {
        enumerator_ptr(lazy)->size = rb_block_proc();
    }
    return lazy;
}
            
find_all() click to toggle source
 
               static VALUE
lazy_select(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy select without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_select_func, 0),
                           Qnil, 0);
}
            
flat_map { |obj| block } → a_lazy_enumerator click to toggle source

Returns a new lazy enumerator with the concatenated results of running block once for every element in lazy.

["foo", "bar"].lazy.flat_map {|i| i.each_char.lazy}.force
#=> ["f", "o", "o", "b", "a", "r"]

A value x returned by block is decomposed if either of the following conditions is true:

a) <i>x</i> responds to both each and force, which means that
   <i>x</i> is a lazy enumerator.
b) <i>x</i> is an array or responds to to_ary.

Otherwise, x is contained as-is in the return value.

[{a:1}, {b:2}].lazy.flat_map {|i| i}.force
#=> [{:a=>1}, {:b=>2}]
 
               static VALUE
lazy_flat_map(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy flat_map without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_flat_map_func, 0),
                           Qnil, 0);
}
            
grep(p1) click to toggle source
 
               static VALUE
lazy_grep(VALUE obj, VALUE pattern)
{
    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         rb_block_given_p() ?
                                         lazy_grep_iter : lazy_grep_func,
                                         pattern),
                           rb_ary_new3(1, pattern), 0);
}
            
lazy() click to toggle source
 
               static VALUE
lazy_lazy(VALUE obj)
{
    return obj;
}
            
map() click to toggle source
 
               static VALUE
lazy_map(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy map without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_map_func, 0),
                           Qnil, lazy_receiver_size);
}
            
reject() click to toggle source
 
               static VALUE
lazy_reject(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy reject without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_reject_func, 0),
                           Qnil, 0);
}
            
select() click to toggle source
 
               static VALUE
lazy_select(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy select without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_select_func, 0),
                           Qnil, 0);
}
            
slice_before(*args) click to toggle source
 
               static VALUE
lazy_super(int argc, VALUE *argv, VALUE lazy)
{
    return enumerable_lazy(rb_call_super(argc, argv));
}
            
take(p1) click to toggle source
 
               static VALUE
lazy_take(VALUE obj, VALUE n)
{
    long len = NUM2LONG(n);
    VALUE lazy;

    if (len < 0) {
        rb_raise(rb_eArgError, "attempt to take negative size");
    }
    if (len == 0) {
        VALUE len = INT2NUM(0);
        lazy = lazy_to_enum_i(obj, sym_cycle, 1, &len, 0);
    }
    else {
        lazy = rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_take_func, n);
    }
    return lazy_set_method(lazy, rb_ary_new3(1, n), lazy_take_size);
}
            
take_while() click to toggle source
 
               static VALUE
lazy_take_while(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy take_while without a block");
    }
    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_take_while_func, 0),
                           Qnil, 0);
}
            
to_enum(method = :each, *args) → lazy_enum click to toggle source
to_enum(method = :each, *args) {|*args| block} → lazy_enum

Similar to Kernel#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 Kernel#to_enum:

# See Kernel#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]
 
               static VALUE
lazy_to_enum(int argc, VALUE *argv, VALUE self)
{
    VALUE lazy, meth = sym_each;

    if (argc > 0) {
        --argc;
        meth = *argv++;
    }
    lazy = lazy_to_enum_i(self, meth, argc, argv, 0);
    if (rb_block_given_p()) {
        enumerator_ptr(lazy)->size = rb_block_proc();
    }
    return lazy;
}
            
zip(*args) click to toggle source
 
               static VALUE
lazy_zip(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary, v;
    long i;
    rb_block_call_func *func = lazy_zip_arrays_func;

    if (rb_block_given_p()) {
        return rb_call_super(argc, argv);
    }

    ary = rb_ary_new2(argc);
    for (i = 0; i < argc; i++) {
        v = rb_check_array_type(argv[i]);
        if (NIL_P(v)) {
            for (; i < argc; i++) {
                if (!rb_respond_to(argv[i], id_each)) {
                    rb_raise(rb_eTypeError, "wrong argument type %s (must respond to :each)",
                        rb_obj_classname(argv[i]));
                }
            }
            ary = rb_ary_new4(argc, argv);
            func = lazy_zip_func;
            break;
        }
        rb_ary_push(ary, v);
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         func, ary),
                           ary, lazy_receiver_size);
}
            

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