Feature #13122
closedSpecial syntax for Hash#default_proc
Description
The current Hash#default_proc flow usually looks something like this:
my_hash = { key: "value" }
my_hash.default_proc = proc { |h, k| h[k] = "other value" }
This makes the common practice of freezing large constant hashes unwieldy. For example,
this:
MY_HASH = {
key: "value"
}.freeze
needs to become
MY_HASH = {
key: "value"
}
MY_HASH.default_proc = proc { |h, k| h[k] = "other value" }
MY_HASH.freeze
if a default_proc
is used.
I propose a new syntax for setting the default_proc within the hash-declaration itself:
my_hash = {
key: "value"
*: proc { |h, k| h[k] = "other value" }
}
*:
as a hash-key is currently a syntax error, so I think there's space in the language for this. Of course, this should also support rocket-style:
my_hash = {
"key" => "value"
* => proc { |h, k| h[k] = "other value" }
}
(I'm completely open to alternative syntaxes, *
just comes to mind because of wildcarding).
I'm happy to attempt work on this, if this feature is desired. I have experience with MRI's API, but not with writing new syntax (which I assume would go in parse.y), so I'd appreciate the help of someone who's familiar with the intricacies of parse.y.
Best,
William Woodruff