[ruby-core:90798] [Ruby trunk Bug#15483] Proc or Method combination with Symbol

[ruby-core:90798] [Ruby trunk Bug#15483] Proc or Method combination with Symbol

[aycabta]

Issue #15483 has been reported by aycabta (aycabta .).

----------------------------------------
Bug #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483

* Author: aycabta (aycabta .)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
In [Feature #6284](is titled "Add composition for procs"), 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/

[ruby-core:90804] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[shevegen]

Issue #15483 has been updated by shevegen (Robert A. Heiler).


I am biased so I do not want to digress from this thread too much while explaining my bias. However had,
I still want to state a few things:

- In regards to Symbol, this is a language design decision, how Symbols are to be used. I think we can
have valid arguments for both main variants, e. g. to keep Symbols simple, or to allow more flexibility.
Personally I'd rather prefer them simple, largely because I don't feel most proposals for change make
them better and most definitely not prettier; but I have no real problem either way here.

Still, in regards to proposals allowing for more flexibility of Symbols, this leads me to:

- **Syntax consideration**. To me personally the proposed syntax is not very elegant.

In particular:

    .map(&(&:to_i >> &:chr))

Is really not pretty. We use '& three' times there; and the new >>. It does not really feel consistent
with other parts of ruby in my opinion, syntax-wise alone. I have less of a problem with a single & but
I also dislike that I have to look carefully, e. g to distinguish between a** .map(&:)** versus a **.map(&)**
variant. Do we really want to have to look for & now carefully and a : or no :, on top of it? The second
variant also packs a lot more information into the method-call, which makes it a bit hard to see what
is going on to me, e. g. **.map(&(&:to_i >> :chr.to_proc)))**. And the >> which I am also not a big fan of,
but as said in the beginning, I am biased already, so my comments will be biased as well.

- Another issue I have, and this is more general, that I do not really see the massive benefit. This is not
solely confined to the proposal here, and is obviously subject to  personal opinion/evaluation and how
you use ruby ("more than one way to use ruby", too), but more generally about some other related
proposals too, where I am not really sure if the change is needed or provides a lot of really useful
things that we need.

I understand it if the goal is more flexibility in what we can do; for example, I think I also stated before
that I am in agreement with proposals to allow arguments to methods given rather than solely be able
to use e. g.  .map(&:method SOME WAY FOR ARGUMENTS HERE). The major problem I have with most
of these proposals I have seen so far is syntax-wise. We do not have that many characters while staying
in ASCII land, but the core of ruby is very elegant and quite simple, syntax-wise (for me). Several of the
proposals in the last ~3 years or so, are, to me, syntax-wise, not really elegant. Syntax is not everything
but if I have to stare at code a lot then I'd rather look at good syntax than bad one.

Anyway, I'll close my comment here.

----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-75978

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90930] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[manga.osyo]

Issue #15483 has been updated by osyo (manga osyo).


I am thinking like this.

NOTE: Here we define it as follows.

* functional object
  * defined `#call` (and `#<<` `#>>`) object
  * e.g. `Proc` `Method`
* blockable object
  * defined `#to_proc` object
  * e.g. `Symbol` `Hash`


## Current

* `Proc#<<` and `Proc#>>` arguments is functional object
  * call `#call`.
* `Proc#<<` and `Proc#>>` is not call `#to_proc`
* `Proc#<<` and `Proc#>>` is not accept block argument


## Composite function in Ruby

* Composite function is functional object and functional object
* `functional object >> functional object # => OK
* `functional object >> other object` # => NG
* `other object >> functional object` # => NG


## `Symbol` is functional object

* `Symbol` is blockable object
* `Symbol` is not functional object
* Handling `Symbol` with compositing functions is incorrect
* What about other blockable objects?
  * e.g. `Hash`
  * `Hash` is functional object?


## `Proc#<<` is call `#to_proc` ?

* It should be explicitly converted to `Proc` (functional object) with` # to_proc`
  * `proc << :hoge` => NG: `:hoge` is not `Proc`
  * `proc << :hoge.to_proc` => OK : Explicitly convert `:hoge` to `Proc`
* Same as not handling `"42"` as a `Integer`
  * `1 + "42"` =>  NG : `"42"` is not `Integer`
  * `1 + "42".to_i` => OK : Explicitly convert `"42"` to `Proc`


## Proposal1 : `Symbol` to functional object

* define `Symbol#>>` `Symbol#<<` `Symbol#call`
* What about other blockable objects?
  * `Hash` is functional object?
* Is it really necessary for `Symbol` ?
* Is `Symbol` really a "functinal object" ?

```ruby
# Symbol to functional object
class Symbol
	def call(*args, &block)
		to_proc.call(*args, &block)
	end

	def <<(other)
		to_proc << other
	end

	def >>(other)
		to_proc >> other
	end
end

p %w{72 101 108 108 111}.map(&(:to_i >> :chr))
# => ["H", "e", "l", "l", "o"]
```


## Proposal2 : `Symbol` to functional object

* `Proc#<<(other)` to `Proc#<<(other, &block)`
* Prioritize `other` ?

```ruby
class Proc
	prepend Module.new {
		def <<(other = nil, &block)
			# other or block?
			super(other || block)
		end

		def >>(other = nil, &block)
			# other or block?
			super(other || block)
		end
	}
end

# :to_i convert to Proc
# must be `.>>`
p %w{72 101 108 108 111}.map(&(:to_i.to_proc.>> &:chr))
# => ["H", "e", "l", "l", "o"]
```


## Proposal3 : Define syntax sugar for `#to_proc`

* For example, define `#to_proc` to `@~`.
  * or other Unary operator
  * `@+` `@-` `@!` `&` ?
* Do not change current specifications
* I think this is good

```ruby
# Add ~@
class Object
	# ~ is to_proc
	# ~ or other unary operator?
	def ~@
		to_proc
	end
end

# Use Symbol#to_proc
p %w{72 101 108 108 111}.map(&(:to_i.to_proc >> :chr.to_proc))

# alias ~ is to_proc
p %w{72 101 108 108 111}.map(&~:to_i >> ~:chr)
```

Thank you :)

[Japanese](https://gist.github.com/osyo-manga/1725a4a670aac54452eca92269a3822b)


----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76128

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90936] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[nobu]

Issue #15483 has been updated by nobu (Nobuyoshi Nakada).


Why not using refinements?

```ruby
# symbol/functionalized.rb
module Symbol::Functionalized
  refine(Symbol) do
    def call(*args, &block)
      to_proc.call(*args, &block)
    end

    def <<(other = (b = true), &block)
      to_proc << (b ? block : other.to_proc)
    end

    def >>(other = (b = true), &block)
      to_proc >> (b ? block : other.to_proc)
    end
  end
end
```

```ruby
require 'symbol/functionalized'
using Symbol::Functionalized

p %w{72 101 108 108 111}.map(&:to_i >> :chr) #=> ["H", "e", "l", "l", "o"]
```


----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76134

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90938] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[manga.osyo]

Issue #15483 has been updated by osyo (manga osyo).


hi, nobu :)

> 引用
Why not using refinements?

It is example code.
Also, `Symbol#call` is not called in `Proc#<<`.

```ruby
# Error: undefined method `call' for :chr:Symbol (NoMethodError)
p %w{72 101 108 108 111}.map(&proc { |s| s.to_i } >> :chr) #=> ["H", "e", "l", "l", "o"]
```


----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76138

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90939] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[nobu]

Issue #15483 has been updated by nobu (Nobuyoshi Nakada).


```ruby
# symbol/functionalized.rb
module Symbol::Functionalized
  refine(Symbol) do
    def call(*args, &block)
      to_proc.call(*args, &block)
    end

    def <<(other = (b = true), &block)
      to_proc << (b ? block : other.to_proc)
    end

    def >>(other = (b = true), &block)
      to_proc >> (b ? block : other.to_proc)
    end
  end

  refine(Proc) do
    def <<(other)
      super(other.to_proc)
    end

    def >>(other)
      super(other.to_proc)
    end
  end
end
```

----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76139

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90944] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[nobu]

Issue #15483 has been updated by nobu (Nobuyoshi Nakada).


I made [function-composite](https://rubygems.org/gems/function-composite) gem.

----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76146

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90945] [Ruby trunk Feature#15483] Proc or Method combination with Symbol

[manga.osyo]

Issue #15483 has been updated by osyo (manga osyo).


I think it will not work in the following cases.

```ruby
# NG: Error undefined method `call' for :chr:Symbol (NoMethodError)
p (30.method(:+) >> :chr).call 42


h = { Alice: 30, Bob: 60, Cris: 90 }

# OK
p (:to_sym >> h).call "Alice"
# => 30

# NG
p (h << :to_sym).call "Bob"
```

Would you like to add `Method#>>` and `Hash#>>`, or other object `#>>` definitions?
I do not think that is good.
I think it is necessary to clearly separate "functional object"(e.g. `Proc`, `Method`) and "blockable object"(e.g. `Symbol`, `Hash`).
I think that it should handle only `functional object` in the composite function.


----------------------------------------
Feature #15483: Proc or Method combination with Symbol
https://bugs.ruby-lang.org/issues/15483#change-76147

* Author: aycabta (aycabta .)
* Status: Open
* 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/

[ruby-core:90968] [Ruby trunk Feature#15483][Rejected] Proc or Method combination with Symbol

[matz]

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/