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Add Enumerator::Lazy docs.

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* explanation of the class concept, with examples;
  * docs for all class methods (most of them just say "Like Enumerable#<methodname>, but chains operation to be lazy-evaluated.", but I believe they are useful this way because now have proper call-sequences and link to corresponding Enumerable's explanations)
  * simplified example for ::new to emphasize the main concept
  * Enumerable#lazy docs are slightly lightened and linked to this class for more in-depth explanations.

  [Misc #15529][ruby-core:91046]

  Co-authored-by: zverok <zverok.offline@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67320 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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hsbt 2019-03-20 23:32:11 +00:00
parent e8e1f72d8f
commit f2ea705d68
1 changed files with 221 additions and 26 deletions
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247
enumerator.c
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@ -1593,6 +1593,57 @@ lazy_generator_init(VALUE enumerator, VALUE procs)
return generator;
}
/*
* Document-class: Enumerator::Lazy
* Enumerator::Lazy is a special type of Enumerator, that allows constructing
* chains of operations without evaluating them immediately, and evaluating
* values on as-needed basis. In order to do so it redefines most of Enumerable
* methods so that they just construct another lazy enumerator.
*
* Enumerator::Lazy can be constructed from any Enumerable with Enumerable#lazy
* method.
*
*
* lazy = (1..Float::INFINITY).lazy.select(&:odd?).drop(10).take_while { |i| i < 30 }
* # => #<Enumerator::Lazy: #<Enumerator::Lazy: #<Enumerator::Lazy: #<Enumerator::Lazy: 1..Infinity>:select>:drop(10)>:take_while>
*
* The real enumeration is performed when any of non-redefined Enumerable methods
* is called, like Enumerable#first on Enumerable#to_a (the latter is aliased as
* #force for more semantical code):
*
* lazy.first(2)
* #=> [21, 23]
*
* lazy.force
* #=> [21, 23, 25, 27, 29]
*
* Note that most of Enumerable methods that could be called with or without block,
* on Enumerator::Lazy will always require block:
*
* [1, 2, 3].map #=> #<Enumerator: [1, 2, 3]:map>
* [1, 2, 3].lazy.map # ArgumentError: tried to call lazy map without a block
*
* This class allows idiomatic calculations on long or infinite sequence, as well
* as chaining of calculations without constructing intermediate arrays.
*
* Example of working with slowly calculated sequence:
*
* require 'open-uri'
*
* # This will fetch all URLs before selecting
* # necessary data
* URLS.map { |u| JSON.parse(open(u).read) }.
* select { |data| data.key?('stats') }.
* first(5)
*
* # This will fetch URLs one-by-one, only till
* # there is enough data to satisfy the condition
* URLS.lazy.map { |u| JSON.parse(open(u).read) }.
* select { |data| data.key?('stats') }.
* first(5)
*
*/
/*
* call-seq:
* Lazy.new(obj, size=nil) { |yielder, *values| ... }
@ -1600,26 +1651,17 @@ lazy_generator_init(VALUE enumerator, VALUE procs)
* 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:
* For example, to create a "filter+map" enumerator:
*
* module Enumerable
* def filter_map(&block)
* map(&block).compact
* def filter_map(sequence)
* Lazy.new(sequence) do |yielder, *values|
* result = yield *values
* yielder << result if result
* 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]
* filter_map(1..Float::INFINITY) {|i| i*i if i.even?}.first(5)
* #=> [4, 16, 36, 64, 100]
*/
static VALUE
lazy_initialize(int argc, VALUE *argv, VALUE self)
@ -1724,11 +1766,9 @@ lazy_add_method(VALUE obj, int argc, VALUE *argv, VALUE args, VALUE memo,
* call-seq:
* e.lazy -> lazy_enumerator
*
* Returns a lazy enumerator, whose methods map/collect,
* flat_map/collect_concat, select/find_all, reject, grep, grep_v, zip, take,
* take_while, drop, and drop_while enumerate values only on an
* as-needed basis. However, if a block is given to zip, values
* are enumerated immediately.
* Returns an Enumerator::Lazy, which redefines most of Enumerable
* methods to postpone enumeration and enumerate values only on an
* as-needed basis.
*
* === Example
*
@ -1774,11 +1814,11 @@ lazy_to_enum_i(VALUE obj, VALUE meth, int argc, const VALUE *argv, rb_enumerator
* lzy.to_enum(method = :each, *args) {|*args| block} -> lazy_enum
* lzy.enum_for(method = :each, *args){|*args| block} -> lazy_enum
*
* Similar to Kernel#to_enum, except it returns a lazy enumerator.
* 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 Kernel#to_enum:
* For example, continuing from the example in Object#to_enum:
*
* # See Kernel#to_enum for the definition of repeat
* r = 1..Float::INFINITY
@ -1846,6 +1886,19 @@ static const lazyenum_funcs lazy_map_funcs = {
lazy_map_proc, lazy_map_size,
};
/*
* call-seq:
* lazy.collect { |obj| block } -> lazy_enumerator
* lazy.map { |obj| block } -> lazy_enumerator
*
* Like Enumerable#map, but chains operation to be lazy-evaluated.
*
* (1..Float::INFINITY).lazy.map {|i| i**2 }
* #=> #<Enumerator::Lazy: #<Enumerator::Lazy: 1..Infinity>:map>
* (1..Float::INFINITY).lazy.map {|i| i**2 }.first(3)
* #=> [1, 4, 9]
*/
static VALUE
lazy_map(VALUE obj)
{
@ -1922,9 +1975,9 @@ lazy_flat_map_proc(RB_BLOCK_CALL_FUNC_ARGLIST(val, m))
* A value <i>x</i> returned by <i>block</i> 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.
* * 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, <i>x</i> is contained as-is in the return value.
*
@ -1955,6 +2008,14 @@ static const lazyenum_funcs lazy_select_funcs = {
lazy_select_proc, 0,
};
/*
* call-seq:
* lazy.find_all { |obj| block } -> lazy_enumerator
* lazy.select { |obj| block } -> lazy_enumerator
* lazy.filter { |obj| block } -> lazy_enumerator
*
* Like Enumerable#select, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_select(VALUE obj)
{
@ -1977,6 +2038,13 @@ static const lazyenum_funcs lazy_reject_funcs = {
lazy_reject_proc, 0,
};
/*
* call-seq:
* lazy.reject { |obj| block } -> lazy_enumerator
*
* Like Enumerable#reject, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_reject(VALUE obj)
{
@ -2018,6 +2086,14 @@ static const lazyenum_funcs lazy_grep_funcs = {
lazy_grep_proc, 0,
};
/*
* call-seq:
* lazy.grep(pattern) -> lazy_enumerator
* lazy.grep(pattern) { |obj| block } -> lazy_enumerator
*
* Like Enumerable#grep, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_grep(VALUE obj, VALUE pattern)
{
@ -2057,6 +2133,14 @@ static const lazyenum_funcs lazy_grep_v_funcs = {
lazy_grep_v_proc, 0,
};
/*
* call-seq:
* lazy.grep_v(pattern) -> lazy_enumerator
* lazy.grep_v(pattern) { |obj| block } -> lazy_enumerator
*
* Like Enumerable#grep_v, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_grep_v(VALUE obj, VALUE pattern)
{
@ -2129,6 +2213,14 @@ lazy_zip_func(RB_BLOCK_CALL_FUNC_ARGLIST(val, zip_args))
return Qnil;
}
/*
* call-seq:
* lazy.zip(arg, ...) -> lazy_enumerator
* lazy.zip(arg, ...) { |arr| block } -> nil
*
* Like Enumerable#zip, but chains operation to be lazy-evaluated.
* However, if a block is given to zip, values are enumerated immediately.
*/
static VALUE
lazy_zip(int argc, VALUE *argv, VALUE obj)
{
@ -2197,6 +2289,13 @@ static const lazyenum_funcs lazy_take_funcs = {
lazy_take_proc, lazy_take_size,
};
/*
* call-seq:
* lazy.take(n) -> lazy_enumerator
*
* Like Enumerable#take, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_take(VALUE obj, VALUE n)
{
@ -2232,6 +2331,13 @@ static const lazyenum_funcs lazy_take_while_funcs = {
lazy_take_while_proc, 0,
};
/*
* call-seq:
* lazy.take_while { |obj| block } -> lazy_enumerator
*
* Like Enumerable#take_while, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_take_while(VALUE obj)
{
@ -2279,6 +2385,13 @@ static const lazyenum_funcs lazy_drop_funcs = {
lazy_drop_proc, lazy_drop_size,
};
/*
* call-seq:
* lazy.drop(n) -> lazy_enumerator
*
* Like Enumerable#drop, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_drop(VALUE obj, VALUE n)
{
@ -2316,6 +2429,13 @@ static const lazyenum_funcs lazy_drop_while_funcs = {
lazy_drop_while_proc, 0,
};
/*
* call-seq:
* lazy.drop_while { |obj| block } -> lazy_enumerator
*
* Like Enumerable#drop_while, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_drop_while(VALUE obj)
{
@ -2363,6 +2483,14 @@ static const lazyenum_funcs lazy_uniq_funcs = {
lazy_uniq_proc, 0,
};
/*
* call-seq:
* lazy.uniq -> lazy_enumerator
* lazy.uniq { |item| ... } -> lazy_enumerator
*
* Like Enumerable#uniq, but chains operation to be lazy-evaluated.
*/
static VALUE
lazy_uniq(VALUE obj)
{
@ -2371,12 +2499,74 @@ lazy_uniq(VALUE obj)
return lazy_add_method(obj, 0, 0, Qnil, Qnil, funcs);
}
#if 0 /* for RDoc */
/*
* call-seq:
* lazy.chunk { |elt| ... } -> lazy_enumerator
*
* Like Enumerable#chunk, but chains operation to be lazy-evaluated.
*/
static VALUE lazy_chunk(VALUE self)
{
}
/*
* call-seq:
* lazy.chunk_while {|elt_before, elt_after| bool } -> lazy_enumerator
*
* Like Enumerable#chunk_while, but chains operation to be lazy-evaluated.
*/
static VALUE lazy_chunk_while(VALUE self)
{
}
/*
* call-seq:
* lazy.slice_after(pattern) -> lazy_enumerator
* lazy.slice_after { |elt| bool } -> lazy_enumerator
*
* Like Enumerable#slice_after, but chains operation to be lazy-evaluated.
*/
static VALUE lazy_slice_after(VALUE self)
{
}
/*
* call-seq:
* lazy.slice_before(pattern) -> lazy_enumerator
* lazy.slice_before { |elt| bool } -> lazy_enumerator
*
* Like Enumerable#slice_before, but chains operation to be lazy-evaluated.
*/
static VALUE lazy_slice_before(VALUE self)
{
}
/*
* call-seq:
* lazy.slice_when {|elt_before, elt_after| bool } -> lazy_enumerator
*
* Like Enumerable#slice_when, but chains operation to be lazy-evaluated.
*/
static VALUE lazy_slice_when(VALUE self)
{
}
# endif
static VALUE
lazy_super(int argc, VALUE *argv, VALUE lazy)
{
return enumerable_lazy(rb_call_super(argc, argv));
}
/*
* call-seq:
* enum.lazy -> lazy_enumerator
*
* Returns self
*/
static VALUE
lazy_lazy(VALUE obj)
{
@ -3380,6 +3570,11 @@ InitVM_Enumerator(void)
#if 0 /* for RDoc */
rb_define_method(rb_cLazy, "to_a", lazy_to_a, 0);
rb_define_method(rb_cLazy, "chunk", lazy_chunk, 0);
rb_define_method(rb_cLazy, "chunk_while", lazy_chunk_while, 0);
rb_define_method(rb_cLazy, "slice_after", lazy_slice_after, 0);
rb_define_method(rb_cLazy, "slice_before", lazy_slice_before, 0);
rb_define_method(rb_cLazy, "slice_when", lazy_slice_when, 0);
#endif
rb_define_alias(rb_cLazy, "force", "to_a");