Feature #15286
closedProposal: Add Kernel.#expand(*args)
Description
This is a suggestion for Hash shorthand.
Kernel.#expand(*args)
is expand local variable
and method
to Hash.
*args
is method or local variable names.
Example¶
def meth
"meth"
end
a, b, c = 1, 2, 3
# #expand args is local variable or method names
# Expand to { a: a, b: b: meth: meth }
p expand(:a, :b, :meth)
# => {:a=>1, :b=>2, :meth=>"meth"}
# Error: `expand': undefined method `hoge' for main:Object (NoMethodError)
p expand(:hoge)
What can be expanded,
- local variable
- method
and, If there are duplicate names, prioritize local variable.
def meth
"meth"
end
meth = 42
p expand(:meth)
# => {:meth=>42}
pull request: https://github.com/ruby/ruby/pull/2006
Updated by shevegen (Robert A. Heiler) almost 6 years ago
I think one possible question in regards to the suggestion here is whether the above method may be useful
on its own, even without a shorthand syntax for Hash. (This is really just a question; I personally am
not having any strong pro/con opinion.)
I also understand that using a method is different compared to the other two proposals. For example,
{ a }
{ a: a}
and
{x, y}
{x: x, y: y}
is different to:
meth = 42
p expand(:meth) # => {:meth=>42}
So using a method is different to the other two proposals (in the two older
issue request, by Ignatius and Shugo Maeda). Perhaps one or more use cases
could be described for a new method to be useful even without the hash
shorthand notation? I can not think of a good one right now but perhaps others
have some ideas.
Updated by osyo (manga osyo) almost 6 years ago
Thanks for comment, shevegen.
Kernel.#expand
can be used as follows.
names = [:a, :b, :meth]
# expand(:a, :b, :meth)
expand(*names)
# => {:a=>1, :b=>2, :meth=>"meth"}
# ???
{ *names }
Updated by nobu (Nobuyoshi Nakada) almost 6 years ago
Interesting feature, but I don't think the name Kernel#expand
is acceptable.
Maybe an instance method of Binding
?
And I think it should raise a NameError
instead of a NoMethodError
on invalid names.
Updated by nobu (Nobuyoshi Nakada) almost 6 years ago
And, what do you expect for keywords, e.g., __FILE__
, __LINE__
, self
, super
, and etc?
Updated by osyo (manga osyo) almost 6 years ago
Thanks nobu :)
Interesting feature, but I don't think the name Kernel#expand is acceptable.
Yes, I looking for a more good name.
Are there any good names?
Maybe an instance method of Binding?
Yes..., but binding.expand(:a, :b, :c)
is long...
Kernel.#expand
got the idea from Kernel.#local_variables
.
And I think it should raise a NameError instead of a NoMethodError on invalid names.
OK, I try :)
And, what do you expect for keywords, e.g., FILE, LINE, self, super, and etc?
Yes, I think it is necessary to discuss what to "expand".
This is a simple implementation with methods and local variables
Updated by matz (Yukihiro Matsumoto) almost 6 years ago
- Related to Feature #15236: add support for hash shorthand added
Updated by matz (Yukihiro Matsumoto) almost 6 years ago
- Status changed from Open to Rejected
I am against the idea for some reasons:
- I don't think
expand
is the right name for the behavior - meta-programming is too much for this half-baked substitute for #15236
Regarding #15236, we are waiting for the time when our recognition changed to accept the JS behavior. Currently, we (at least me) recognize {a,b,c}
as a literal for a set, not a shorthand for {a:a,b:b,c:c}
. I am neutral. I don't want Ruby to follow every JS behavior.
Matz.
Updated by osyo (manga osyo) almost 6 years ago
OK, Thank you, matz :)