Bug #4914: Array#index fails when used in if statement assignment

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

[bterkuile (Benjamin ter Kuile)]

cat /etc/issue: Ubuntu 11.04
rvm -v: rvm 1.6.2
rvm 1.9.2, ruby -v: ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]
Also tested with: rvm 1.9.2-head, ruby -v: ruby 1.9.2p274 (2011-06-06 revision 31932) [x86_64-linux]

Test code:

a = [:a, :b, :c]
for k in 'a'..'c'
if i = a.index(k.to_sym) && k.to_s =~ /b/
puts i
end
end
for k in 'a'..'c'
i = a.index(k.to_sym)
if i && k.to_s =~ /b/
puts i
end
end

output:
0
1

expected output:
1
1

[mfn (Markus Fischer)]

It "works" for me if you change the && to and; so I think it's a precedence issue you're facing here.

I think this blog post here has some good examples which I think directly apply to your case: http://blog.jayfields.com/2007/08/ruby-operator-precedence-of-and-which.html

[matz (Yukihiro Matsumoto)]

• Status changed from Open to Rejected

not a bug. run the following:

a = [:a, :b, :c]
for k in 'a'..'c'
if i = a.index(k.to_sym) && k.to_s =~ /b/
puts i
end
end
for k in 'a'..'c'
if i = (a.index(k.to_sym) && k.to_s =~ /b/)
puts i
end
end
for k in 'a'..'c'
if (i = a.index(k.to_sym)) && k.to_s =~ /b/
puts i
end
end
for k in 'a'..'c'
i = a.index(k.to_sym)
if i && k.to_s =~ /b/
puts i
end
end

[judofyr (Magnus Holm)]

Ruby parses your code like this:

if i = (a.index(k.to_sym) && k.to_s =~ /b/)

You can fix this by using "and" or explicit parenthesis:

if i = a.index(k.to_sym) and k.to_s =~ /b/
if (i = a.index(k.to_sym)) && k.to_s =~ /b/

// Magnus Holm

On Tue, Jun 21, 2011 at 22:28, Benjamin ter Kuile [e-mail] wrote:

Issue #4914 has been reported by Benjamin ter Kuile.

---

Bug #4914: Array#index fails when used in if statement assignment
http://redmine.ruby-lang.org/issues/4914

Author: Benjamin ter Kuile
Status: Open
Priority: Normal
Assignee:
Category:
Target version:
ruby -v: 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

cat /etc/issue: Ubuntu 11.04
rvm -v: rvm 1.6.2
rvm 1.9.2, ruby -v: ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]
Also tested with: rvm 1.9.2-head, ruby -v: ruby 1.9.2p274 (2011-06-06 revision 31932) [x86_64-linux]

Test code:

a = [:a, :b, :c]
for k in 'a'..'c'
 if i = a.index(k.to_sym) && k.to_s =~ /b/
   puts i
 end
end
for k in 'a'..'c'
 i = a.index(k.to_sym)
 if i && k.to_s =~ /b/
   puts i
 end
end

output:
0
1

expected output:
1
1

--
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