Found table http://phrogz.net/programmingruby/language.html#table_18.4 but unable to find description for |=
How the |= assignment operator works?
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4 Answers
When working with arrays |= is useful for uniquely appending to an array.
>> x = [1,2,3]
>> y = [3,4,5]
>> x |= y
>> x
=> [1, 2, 3, 4, 5]
Comments
Bitwise OR assignment.
x |= y
is shorthand for:
x = x | y
(just like x += y is shorthand for x = x + y).
1 Comment
mynameiscoffey
Bah, my bad, thanks for the correction. Updated my answer to reflect bitwise or, not logical or.
With the exception of ||= and &&= which have special semantics, all compound assignment operators are translated according to this simple rule:
a ω= b
is the same as
a = a ω b
Thus,
a |= b
is the same as
a = a | b
5 Comments
mynameiscoffey
In what ways does
x ||= y differ from x = x || y ?
Jeremy Moritz
As far as i can tell,
||= and &&= are not exceptions. They both seem to function identically to a = a || b and a = a && b, respectively. If there are any exceptions to this, can you please provide an example?
Jörg W Mittag
@JeremyMoritz: If
a is a setter (e.g. foo.bar=), then a = a || b will always call both the setter and the getter, whereas a ||= b will only call the setter if a is falsey (or truthy in the case of &&=). In other words: I can write a program which can output whether you used ||= or = … || …, therefore the two are not equivalent.Jörg W Mittag
@JeremyMoritz: Note that this is a bug in the ISO Ruby Language Specification. The ISO spec says that all operator assignments
a ω= b for all operators ω are evaluated AS-IF they were written as a = a ω b, but that is only true for operators other than || and &&.Jeremy Moritz
Thank you @JörgWMittag for the detailed explanation!
It is listed in the link you provided. It's an assignment combined with bitwise OR. Those are equivalent:
a = a | b
a |= b
