[#66126] Creation/Conversion methods/functions table for Ruby types — SASADA Koichi <ko1@...>
Hi,
5 messages
2014/11/07
[#66248] [ruby-trunk - Feature #10423] [PATCH] opt_str_lit*: avoid literal string allocations — normalperson@...
Issue #10423 has been updated by Eric Wong.
3 messages
2014/11/13
[#66595] [ruby-trunk - Bug #10557] [Open] Block not given when the argument is a string — bartosz@...
Issue #10557 has been reported by Bartosz Kopinski.
3 messages
2014/11/30
[ruby-core:66347] [ruby-trunk - Feature #10498] Make `loop` yield a counter
From:
shortcutter@...
Date:
2014-11-18 14:47:33 UTC
List:
ruby-core #66347
Issue #10498 has been updated by Robert Klemme.
Franck Verrot wrote:
> Hi Robert, thanks for taking time reading the ticket.
You're welcome!
> Robert Klemme wrote:
> > I am actually against this feature. Reason: an infinite loop does not need a counter.
>
> Most examples I can find about it (and use personally when teaching) make use of a counter (all languages). Keeping track of the current iteration can be useful.
"can"!
> > We incur the cost of counting (especially when the figure leaves Fixnum space) on all infinite loops.
>
> I definitely agree . I wasn't able to find a way to fine-tune this based on the block's arity as mentioned previously.
That seems fairly easy:
~~~
def lp(&b)
return to_enum(:lp) unless b
if b.arity == 0
while true
b[]
end
else
i = 0
while true
b[i]
i += 1
end
end
raise "This must never happen"
end
~~~
> On the other hand, you'd need 4,611,686,018,427,387,903 iterations before paying the price of using `BigNum`s, which compared to the code you're having in the block would probably be more expensive than incrementing a `BigNum`.
Yes, but as a user of loop you would not have a choice any more. I'd rather use the approach from above or define another method loop_with_index or use the approach with Generator and a constant. I would definitively not unconditionally provide a counter.
> So I'm not sure whether or not that price should be considered high. Anything I'm missing?
I think it is generally bad to do unnecessary work. Also it is inelegant. :-)
----------------------------------------
Feature #10498: Make `loop` yield a counter
https://bugs.ruby-lang.org/issues/10498#change-50001
* Author: Franck Verrot
* Status: Open
* Priority: Normal
* Assignee: ruby-core
* Category: core
* Target version: current: 2.2.0
----------------------------------------
# Problem
Teaching Ruby, we always end up with that type of construct
```ruby
i = 0
loop do
i += 1
# do something with i....
raise StopIteration if i ...
end
```
# Solution
What I propose with this patch is making `loop` yield the iteration count:
```ruby
loop do |i|
# do something with i....
raise StopIteration if i ...
end
```
`i` starts at 0 and stops at `FIXNUM_MAX` (there's no `Float::Infinity` equivalent for integers).
# Alternate solution
`Integer#times` could work if we had an `<Integer's infinity>` object, so we would just do `<Integer's Infinity>.times { |i| ... }`.
Also, this is the very first patch I submit to Ruby, I might have done something horrible, feel free to tell me :-)
---Files--------------------------------
0001-vm_eval.c-loop-now-yields-a-incremented-counter.patch (1.74 KB)
0001-vm_eval.c-loop-now-yields-a-incremented-counter.patch (1.86 KB)
--
https://bugs.ruby-lang.org/