| versus || Any reason for this issue?

[Iñaki Baz Castillo]

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Pgo=

 

[Florian Gilcher]

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Hi, why in the second case the non declared "my_var" variable is
processed but not in the first case?

irb> nil || 2 || my_var
=3D> 2

irb> nil | 2 | my_var
NameError: undefined local variable or method `my_var'


Of course, I prefer the first case: 2 is already true so there is no
reason to read the next "my_var". Also, it's not good for performance,
is it?

| is the bitwise OR and something entirely different from ||. | needs =20=

to evaluate both Operands while the value of a logical OR (||) is =20
known at the moment that one of the Operands is true.

Regards
Florian Gilcher
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[Robert Klemme]

Hi, why in the second case the non declared "my_var" variable is
processed but not in the first case?

Because || does short circuit while | does not.

irb> nil || 2 || my_var
=> 2

irb> nil | 2 | my_var
NameError: undefined local variable or method `my_var'

Of course, I prefer the first case: 2 is already true so there is no
reason to read the next "my_var". Also, it's not good for performance,
is it?

"||" is the short circuit boolean "or" operator. You cannot override
it. "|" on the other hand is an operator that can be overloaded and it
does not short circuit. It would not make any sense to make "|" short
circuit because it can contain arbitrary functionality.

Here are some classes that implement "|":

$ ruby -e 'ObjectSpace.each_object(Module) {|cl| p cl if
cl.instance_methods.include? "|"}'
Array
Bignum
Fixnum
FalseClass
TrueClass
NilClass

Kind regards

robert

 

[Robert Klemme]

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| is the bitwise OR and something entirely different from ||.

This is only mostly correct. Semantics of | depend on the class that
implements it.

irb(main):001:0> %w{a b c} | %w{c d e}
=> ["a", "b", "c", "d", "e"]
irb(main):002:0> %w{a b c} & %w{c d e}
=> ["c"]

Cheers

robert