Re: A very half-baked idea: setting local variables

On Mon, Jul 8, 2013 at 11:06 PM, Hal Fulton <[e-mail]> wrote:

> I'm sure this nonexistent feature is not in great demand, but there have
> been different times that I (and other people) have wanted it.
>
> This is not a "really serious" proposal, but I wanted to see what other
> people's comments were about lengthy multiple assignments and
> how to deal with them.
>
> Sometimes I wish I had an alternative way to do assignment.
>
> Example:
>
>   foo, bar, baz, alpha, beta, gamma, fred, bill, joey = *values
>
> In a case like that, my eye has to scan a long way to the right
> before finding the equal sign and grasping that this is a multiple
> assignment.
>
> I like this better:
>
>   vars = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey]
>   assign values, vars
>
> Note that this wouldn't be a method call (like alias_method) but
> a keyword (like alias) unless "binding of caller" was permitted...
> which is another thing I've wanted but I suppose will never
> happen.
>
> Comments, questions, projectiles?
>

At the moment there is no other way I am aware of to introduce local
variables _at runtime_.  While you can do things like eval("foo = 123") the
remaining code won't be using the local variable.

$ ruby -e 'b=binding;eval("x=10", b);puts x'
-e:1:in `<main>': undefined local variable or method `x' for main:Object
(NameError)
$ ruby -e 'b=binding;eval("x=10", b);eval("puts x", b)'
10


How about

data = {}
[:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill,
:joey].each_with_index do |s,i|
  data[s] = values[i]
end

puts data[:baz]

or even

data = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill,
:joey].each_with_index.each_with_object {} do |(s,i), d|
  d[s] = values[i]
end

?

Cheers

robert

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