Hash again

Following suit with the main trend, talking Hashes :wink:

I was just thinking about the potential impact on syntax
Right now
    {:a => 1, :a => 2}
returns
  {:a => 2}
in my irb

is this defined right now?
And how ought that be handeled in a HistHash?

My personal feelings are that a duplicate hash keys in a hash literal should
raise an Exception for any kind of Hash.

Cheers
Robert

···

--
Deux choses sont infinies : l'univers et la bêtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

Robert Dober wrote:

Following suit with the main trend, talking Hashes :wink:

I was just thinking about the potential impact on syntax
Right now
   {:a => 1, :a => 2}
returns
{:a => 2}
in my irb

is this defined right now?
And how ought that be handeled in a HistHash?

My personal feelings are that a duplicate hash keys in a hash literal should
raise an Exception for any kind of Hash.

The literal probably "compiles" to something like
  foo = Hash.new
  foo[:a] = 1
  foo[:a] = 2

You might want to put that through irb while tracing the interpreter. So, the latest goes, and it's probably fine enough, considering there's only one kind of Hash literal in Ruby. It's probably also faster since parsing the whole literal ahead-of-time to be able to check for duplicate keys would be messy. And imperfect, since the keys in the hash could be results of method calls, so you could only really check for duplicate literal keys. And if you did, then someone would expect there not to be duplicate keys ever in a HistHash (where I presume the result of adding a new value to a key results in something else than replacing the old value - I'm not familiar with the data structure) constructed with a literal, and shoot himself in the foot sooner or later.

David Vallner