Feature #8172
IndexError-returning counterparts to destructive Array methods
Description
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There are a few desctructive (({Array})) methods that take an index as an argument and silently insert (({nil})) if the index is out of range:
a = []; a[1] = :foo; a # => [nil, :foo] [].insert(1, :foo) # => [nil, :foo] [].fill(:foo, 1, 1) # => [nil, :foo]
Among them, (({Array#[]})) has a counterpart that returns an (({IndexError})) when the index is out of range:
[].fetch(1) # => IndexError
and this is useful to avoid bugs that would be difficult to find if (({Array#[]})) were used. However for (({Array#insert})) and (({Array#fill})), there are no such counterparts, and that fact that these methods silently insert (({nil})) is often the cause of a bug that is difficult to find. I suggest there should be some versions of these methods that return (({IndexError})) when index is out of range:
[].insert!(1, :foo) # => IndexError [].fill!(:foo, 1, 1) # => IndexError
I believe this would make debugging easier.
=end
History
Updated by sawa (Tsuyoshi Sawada) over 6 years ago
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In the above, I missed to say that there is no counterpart for (({Array#[]=})). There should be one for it as well, but I cannot think of a good method name.
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Updated by nobu (Nobuyoshi Nakada) over 6 years ago
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(({Hash})) has (({#store})) as an alias of (({#[]=})).
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Updated by duerst (Martin Dürst) over 6 years ago
This may be just an issue of wording: You say "index is out of range".
By definition, Ruby arrays don't have a range. They can grow
dynamically. In many cases, this is a big feature.
Also, you complain about inserting nil. So what about the following case:
a = [1, 2, 3]; a[3] = :foo; a # => [1, 2, 3, :foo]
There is no nil, so maybe this is okay. But the array is expanded.
Should there be an error?
Regards, Martin.
On 2013/03/27 10:51, sawa (Tsuyoshi Sawada) wrote:
Issue #8172 has been reported by sawa (Tsuyoshi Sawada).
Feature #8172: IndexError-returning counterparts to destructive Array methods
https://bugs.ruby-lang.org/issues/8172
Updated by sawa (Tsuyoshi Sawada) over 6 years ago
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Martin
For clarification, I meant to have it return an error only in cases where (({nil})) needs to be inserted otherwise. So cases like the following should not return an error:
a = [1, 2, 3]; a[3] = :foo; a # => (actually it should be a different method name) [1, 2, 3, :foo] [1, 2, 3].insert!(3, :foo) # => [1, 2, 3, :foo] [1, 2, 3].fill!(:foo, 3) # => [1, 2, 3, :foo]
=end
Updated by matz (Yukihiro Matsumoto) over 6 years ago
- Status changed from Open to Feedback
I am not against the idea itself, but using bang (!) for the names is not consistent with other bang methods.
Matz.