[#108552] [Ruby master Bug#18782] Race conditions in autoload when loading the same feature with multiple threads. — "ioquatix (Samuel Williams)" <noreply@...>
Issue #18782 has been reported by ioquatix (Samuel Williams).
11 messages
2022/05/14
[ruby-core:108541] [Ruby master Feature#17316] On memoization
From:
"joel@... (Joel Drapper)" <noreply@...>
Date:
2022-05-13 11:32:06 UTC
List:
ruby-core #108541
Issue #17316 has been updated by joel@drapper.me (Joel Drapper).
I've been experimenting with memoization by passing a block to `attr_reader` / `attr_accessor`, e.g.
```ruby
attr_reader(:foo) { something_slow }
```
or
```ruby
attr_reader :foo do
something_slow
end
```
I prototyped this in Ruby to get a feel for what it's like to use. https://gist.github.com/joeldrapper/7e35f2f5f906344195c121801ddd28d4
----------------------------------------
Feature #17316: On memoization
https://bugs.ruby-lang.org/issues/17316#change-97585
* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
I have seen so many attempts to memoize a value in the form:
```ruby
@foo ||= some_heavy_calculation(...)
```
improperly, i.e., even when the value can potentially be falsy. This practice is wide spread, and since in most cases memoization is about efficiency and it would not be critical if it does not work correctly, people do not seem to care so much about correcting the wrong usage.
In such case, the correct form would be:
```ruby
unless instance_variable_defined?(:@foo)
@foo = some_heavy_calculation(...)
end
```
but this looks too long, and perhaps that is keeping people away from using it.
What about allowing `Kernel#instance_variable_set` to take a block instead of the second argument, in which case the assignment should be done only when the instance variable is not defined?
```ruby
instance_variable_set(:@foo){some_heavy_calculation(...)}
```
Or, if that does not look right or seems to depart from the original usage of `instance_variable_set`, then what about having a new method?
```ruby
memoize(:foo){some_heavy_calculation(...)}
```
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