Feature #6684
Object#do
Status:
Rejected
Priority:
Normal
Assignee:

Target version:

Description
=begin
#Object#do
This is my first post.
初めての投稿です。よろしくお願いします。
Let me propose a new method Object#do
.
次のような実装のObject#do
を提案します。
class Object def do(*args, &blk) yield(self, *args) end end
do
encapsulate a sequencial procedure into a block. It makes some temporal variables to be block local and enhance code readability. I might say that do
is an Object#tap with block result, or is Array#map for one item.
do
はオブジェクトに対する一連の処理をブロック内に閉じ込めます。それによって、一時変数のブロック内への局所化、コードの可読性向上を実現します。結果を返すObject#tap、単項版Array#mapと見ることができます。
##Usage
# calculate average and standard deviation for list # # without `do` scores = [56, 87, 49, 75, 90, 63, 65] scores.inject(:+) / scores.size # => 69 avg = scores.inject(:+) / scores.size sigmas = scores.map { n (avg  n)**2 } sd = Math.sqrt(sigmas.inject(:+) / scores.size) # => 14.247806848775006 # with `do` avg = [56, 87, 49, 75, 90, 63, 65].do { s s.inject(:+) / s.size } # => 69 sd = scores.do { s avg = s.inject(:+) / s.size sigmas = s.map { n (avg  n)**2 } Math.sqrt(sigmas.inject(:+) / s.size) } sd # => 14.247806848775006 # create a hash from a set of lists # # without `do` h = Hash[ [:a, :b, :c].zip([1, 2, 3]) ] # => {:a=>1, :b=>2, :c=>3} # with `do` h = [:a, :b, :c].zip([1,2,3]).do { arr Hash[arr] } # => {:a=>1, :b=>2, :c=>3} # sum of array using recursion # # without `do` def sum(lst, mem=0) return mem if lst.empty? sum(lst.drop(1), mem+lst.first) end sum [*1..5], 5 # => 20 # or def sum(lst, mem=0) return mem if lst.empty? fst, *tail = lst sum(tail, mem+fst) end # with `do` def sum(lst, mem=0) return mem if lst.empty? lst.do { fst, *tail sum(tail, mem+fst) } end sum2 [*1..5], 5 # => 20
BasicObject#instance_eval works for the above, but it not appropriate for them.
同様の目的はBasicObject#instance_evalでも実現できますが、この種の一般的演算には適さないと考えます。
Thank you for your consideration.
=end
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