From: matz@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:90968] [Ruby trunk Feature#15483][Rejected] Proc or Method combination with Symbol
Date: Thu, 10 Jan 2019 05:38:00 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-76176.20190110053757.a4a120168c66339e@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-15483.20181229104018@ruby-lang.org
Issue #15483 has been updated by matz (Yukihiro Matsumoto).
Status changed from Open to Rejected
I feel the expression `ary.map(&(:to_i << :chr))` is far less readable than `ary.map{|x|x.to_i.chr}`.
And the latter is faster and can take arguments NOW e.g. `ary.map{|x|x.to_i(16).chr}`.
Given these superiorities, this proposal does not sound attractive.
Matz.
p.s.
And this can lead to the default block parameter like `it`.
----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76176
* Author: aycabta (aycabta .)
* Status: Rejected
* Priority: Normal
* Assignee:
* Target version:
----------------------------------------
In [Feature #6284], Matz said
> We need more discussion if we would add combination methods to the Symbol class.
Right, let's get started to discuss.
For your information, recent a few months I'm discussing this with @osyo .
## This is a discussion of "design"
I understand that all features of this issue have both merits and demerits, but I guess that language design is most important. All features of this issue related to each other.
## Abstract
At present, you can use `Proc#>>` or `Proc#<<` with `Symbol#to_proc`.
```ruby
%w{72 101 108 108 111}.map(&(:to_i.to_proc >> :chr.to_proc))
# => ["H", "e", "l", "l", "o"]
```
This is convenient but methods that take block can take a proc with `&` syntax sugar instead of `#to_proc` by right, like `[1, 2, 3].map(&:to_s)`. So `Symbol#to_proc` looks like too long for `Proc#>>` or `Proc#<<`. Therefore, you need new syntax sugar.
## Receiver
### `Symbol#>>` and `Symbol#<<`
`Symbol#>>` and `Symbol#<<` will be considered, but this means that `Symbol` is treated as `Proc` partially. The `[1, 2, 3].map(&:to_s)` treats `Symbol` as `Proc` partially too, but it's with pre-positioned `&`.
```ruby
%w{72 101 108 108 111}.map(&(:to_i >> :chr.to_proc))
# => ["H", "e", "l", "l", "o"]
```
I can't come up with other ideas for the `Symbol` receiver.
### New `&:symbol_name` syntax sugar for `:symbol_name.to_proc`
```ruby
%w{72 101 108 108 111}.map(&(&:to_i >> :chr.to_proc)))
# => ["H", "e", "l", "l", "o"]
```
## Argument
### Calls `#to_proc` by `Proc#>>` or `Proc#<<` internally as a duck typing
```ruby
%w{72 101 108 108 111}.map(&(:to_i.to_proc >> :chr))
# => ["H", "e", "l", "l", "o"]
```
In this case, `Proc#>>`(`:to_i.to_proc >>`) calls `Symbol#to_proc`(for `:chr`) inside.
This is useful to use with `Hash#to_proc`:
```ruby
h = { Alice: 30, Bob: 60, Cris: 90 }
%w{Alice Bob Cris}.map(&(:to_sym.to_proc >> h))
# => [30, 60, 90]
```
### `Proc#>>` and `Proc#<<` take block as an argument
```ruby
%w{72 101 108 108 111}.map(&(:to_i.to_proc >> &:chr))
```
## Combination of receiver and argument
`Symbol#>>` and calling `#to_proc` internally:
```ruby
%w{72 101 108 108 111}.map(&(:to_i >> :chr))
# => ["H", "e", "l", "l", "o"]
```
`&:symbol_name` syntax sugar for `:symbol_name.to_proc` and `Symbol#>>` and taking block:
```ruby
%w{72 101 108 108 111}.map(&(&:to_i >> &:chr))
# => ["H", "e", "l", "l", "o"]
```
--
https://bugs.ruby-lang.org/
prev parent reply other threads:[~2019-01-10 5:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-15483.20181229104018@ruby-lang.org>
2018-12-29 10:40 ` [ruby-core:90798] [Ruby trunk Bug#15483] Proc or Method combination with Symbol aycabta
2018-12-29 12:19 ` [ruby-core:90804] [Ruby trunk Feature#15483] " shevegen
2019-01-08 14:47 ` [ruby-core:90930] " manga.osyo
2019-01-09 5:40 ` [ruby-core:90936] " nobu
2019-01-09 6:48 ` [ruby-core:90938] " manga.osyo
2019-01-09 7:18 ` [ruby-core:90939] " nobu
2019-01-09 10:27 ` [ruby-core:90944] " nobu
2019-01-09 12:37 ` [ruby-core:90945] " manga.osyo
2019-01-10 5:38 ` matz [this message]
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