Feature #16102
Updated by sawa (Tsuyoshi Sawada) over 5 years ago
Since symbols have a `to_proc` method, it is natural to expect that they would appear in a method chain like:
```ruby
:some_symbol.to_proc.call(...)
```
In fact, I have use cases like this:
```ruby
arrays = [["a", "b"], ["c"], ["d", "e"]]
hashes = [{"a" => 1}, {"b" => 2, "c" => 3}, {"d" => 4, "e" => 5}]
:product.to_proc.(*arrays) # => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]
:zip.to_proc.(*arrays) # => [["a", "c", "d"], ["b", nil, "e"]]
:union.to_proc.(*arrays) # => ["a", "b", "c", "d", "e"]
:merge.to_proc.(*hashes) # => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}
```
I request `Symbol#call` to be defined, which would implicitly call `to_proc` on the receiver and then the conventional `Proc#call` on the result. Then, I can do:
```ruby
:product.(*arrays) # => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]
:zip.(*arrays) # => [["a", "c", "d"], ["b", nil, "e"]]
:union.(*arrays) # => ["a", "b", "c", "d", "e"]
:merge.(*hashes) # => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}
```
This would solve what proposals #6499, #7444, #8970, #11262 aim to do.
Notice that proposals #12115 and #15301 ask for `Symbol#call`, but they ask for different things (a method that returns a proc), and are irrelevant to the current proposal.