From: "sawa (Tsuyoshi Sawada)" <sawadatsuyoshi@...>
Date: 2013-03-27T11:55:43+09:00
Subject: [ruby-core:53762] [ruby-trunk - Feature #8172] IndexError-returning counterparts to destructive Array methods


Issue #8172 has been updated by sawa (Tsuyoshi Sawada).


=begin
> 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
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Feature #8172: IndexError-returning counterparts to destructive Array methods
https://bugs.ruby-lang.org/issues/8172#change-37960

Author: sawa (Tsuyoshi Sawada)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


=begin
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


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