* [ruby-core:99042] [Ruby master Feature#17006] Let `Kernel#Hash` take a block to provide the default value
@ 2020-07-03 8:09 sawadatsuyoshi
2020-07-04 7:36 ` [ruby-core:99050] " nobu
2020-07-04 7:51 ` [ruby-core:99051] " sawadatsuyoshi
0 siblings, 2 replies; 3+ messages in thread
From: sawadatsuyoshi @ 2020-07-03 8:09 UTC (permalink / raw
To: ruby-core
Issue #17006 has been reported by sawa (Tsuyoshi Sawada).
----------------------------------------
Feature #17006: Let `Kernel#Hash` take a block to provide the default value
https://bugs.ruby-lang.org/issues/17006
* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
Sometimes, we need to create a hash that has explicit key-value pairs as well as a default value, but there has not been a way to do that at once. The most naive way is to do like this:
```ruby
h = {a: 1, b: 2}
h.default_proc = ->(k, v){raise "Unknown key #{k}"}
h # => ...
```
A more sophisticated way is this:
```ruby
Hash.new{|k, v| raise "Unknown key #{k}"}.merge({a: 1, b: 2})
```
But that is still not short enough, and it also looks backwards, i.e., we usually want to specify the explicit key-value pairs before the default value.
My proposal is to allow `Kernel#Hash` to take a block that provides the default value in the same way as the block of `Hash.new`:
```ruby
Hash({a: 1, b: 2}){|k, v| raise "Unknown key #{k}"}
```
--
https://bugs.ruby-lang.org/
^ permalink raw reply [flat|nested] 3+ messages in thread
* [ruby-core:99050] [Ruby master Feature#17006] Let `Kernel#Hash` take a block to provide the default value
2020-07-03 8:09 [ruby-core:99042] [Ruby master Feature#17006] Let `Kernel#Hash` take a block to provide the default value sawadatsuyoshi
@ 2020-07-04 7:36 ` nobu
2020-07-04 7:51 ` [ruby-core:99051] " sawadatsuyoshi
1 sibling, 0 replies; 3+ messages in thread
From: nobu @ 2020-07-04 7:36 UTC (permalink / raw
To: ruby-core
Issue #17006 has been updated by nobu (Nobuyoshi Nakada).
The description mentions the default value first, but the proposal will solve the default proc only.
----------------------------------------
Feature #17006: Let `Kernel#Hash` take a block to provide the default value
https://bugs.ruby-lang.org/issues/17006#change-86424
* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
Sometimes, we need to create a hash that has explicit key-value pairs as well as a default value, but there has not been a way to do that at once. The most naive way is to do like this:
```ruby
h = {a: 1, b: 2}
h.default_proc = ->(h, k){raise "Unknown key #{k}"}
h # => ...
```
A more sophisticated way is this:
```ruby
Hash.new{|h, k| raise "Unknown key #{k}"}.merge({a: 1, b: 2})
```
But that is still not short enough, and it also looks backwards, i.e., we usually want to specify the explicit key-value pairs before the default value.
My proposal is to allow `Kernel#Hash` to take a block that provides the default value in the same way as the block of `Hash.new`:
```ruby
Hash({a: 1, b: 2}){|h, k| raise "Unknown key #{k}"}
```
--
https://bugs.ruby-lang.org/
^ permalink raw reply [flat|nested] 3+ messages in thread
* [ruby-core:99051] [Ruby master Feature#17006] Let `Kernel#Hash` take a block to provide the default value
2020-07-03 8:09 [ruby-core:99042] [Ruby master Feature#17006] Let `Kernel#Hash` take a block to provide the default value sawadatsuyoshi
2020-07-04 7:36 ` [ruby-core:99050] " nobu
@ 2020-07-04 7:51 ` sawadatsuyoshi
1 sibling, 0 replies; 3+ messages in thread
From: sawadatsuyoshi @ 2020-07-04 7:51 UTC (permalink / raw
To: ruby-core
Issue #17006 has been updated by sawa (Tsuyoshi Sawada).
nobu (Nobuyoshi Nakada) wrote in #note-2:
> The description mentions the default value first, but the proposal will solve the default proc only.
Default value is a special (static) case of default proc, so I think having the latter would be enough:
```ruby
Hash({a: 1, b: 2}){0}
```
If there is concern for efficiency, at least for strings, we can turn on the frozen string mode.
```ruby
# frozen_string_literal: true
Hash({1 => "a", 2 => "b"}){"c"}
```
----------------------------------------
Feature #17006: Let `Kernel#Hash` take a block to provide the default value
https://bugs.ruby-lang.org/issues/17006#change-86425
* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
Sometimes, we need to create a hash that has explicit key-value pairs as well as a default value, but there has not been a way to do that at once. The most naive way is to do like this:
```ruby
h = {a: 1, b: 2}
h.default_proc = ->(h, k){raise "Unknown key #{k}"}
h # => ...
```
A more sophisticated way is this:
```ruby
Hash.new{|h, k| raise "Unknown key #{k}"}.merge({a: 1, b: 2})
```
But that is still not short enough, and it also looks backwards, i.e., we usually want to specify the explicit key-value pairs before the default value.
My proposal is to allow `Kernel#Hash` to take a block that provides the default value in the same way as the block of `Hash.new`:
```ruby
Hash({a: 1, b: 2}){|h, k| raise "Unknown key #{k}"}
```
--
https://bugs.ruby-lang.org/
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-07-04 7:51 ` [ruby-core:99051] " sawadatsuyoshi
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