Will `&&` always run before `if` on the same line in Ruby

Question

Will every && run before if on the same line in Ruby?

For example:

@building.approved = params[:approved] if xyz && abc && mno...

Can an unlimited number of && be used on the right side of an if without using parentheses?

I'm inclined to use parentheses but I'd like to understand the default behaviour.

Possible duplicate of [Ruby operator precedence table](http://stackoverflow.com/questions/21060234/ruby-operator-precedence-table) — Makoto, Sep 29 '16 at 17:46
I don't think this is an exact duplicate of the nominated exemplar: Knowing operator precedence won't help the OP, since `if` is not an operator. — Wayne Conrad, Sep 29 '16 at 17:56

tadman · Accepted Answer · 2016-09-29T17:52:37.590

2

Everything after the if must be part of the condition by virtue of the syntax. The only way to get around this is to be really specific:

(@building.approved = params[:approved] if xyz) && abc && ...

Which is obviously not what you're intending here.

Operator binding strength isn't an issue here since if is a syntax element not an operator, so it has the absolute lowest priority.

The only conditions that will be evaluated are the ones that produce a logically false value, or come after one that was logically true as the first one to return logically false will halt the chain.

That is:

if a && b && c

Will stop at a if that is a logically-false value. b and c will not be evaluated. There's no intrinsic limit on chaining though.

edited Sep 29 '16 at 17:52

answered Sep 29 '16 at 17:49

tadman

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What do you think of adding 'something about short-circuiting and the `&&` operator? It's relevant to the question. – Wayne Conrad Sep 29 '16 at 17:50
@wayneconrad Ah, due to the peculiar wording of the question I've added a note. – tadman Sep 29 '16 at 17:52
Yes, that's the wording that made me think it relevant. I'll delete this comment, and the other one, shortly. – Wayne Conrad Sep 29 '16 at 17:54
Leave it up. I think it helps show the train of thought here. – tadman Sep 29 '16 at 18:05

Will `&&` always run before `if` on the same line in Ruby

1 Answers1