5 ms·

I had to write some ruby at work recently and wasted a few hours on a bug caused by the following footgun: irb(main):028:0> value = false or true => tr

I had to write some ruby at work recently and wasted a few hours on a bug caused by the following footgun: irb(main):028:0> value = false or true => true irb(main):029:0> value => false That really makes me want to write it off entirely. It’s hard to think of a situation where this is the right behavior.

jameskilton 3y ago
You want to use "||" like most languages, not "or". They have different precedence rules.
sinkwool 3y ago
`and`, `or`, `not` have much lower precedence than `&&`, `||` and `!` . I would just avoid `and` and `or` in general. For some more explanation see https://graceful.dev/courses/the-freebies/modules/ruby-language/topic/episode-125-and-or/ https://graceful.dev/courses/the-freebies/modules/ruby-langu...
- djur 3y ago
  Rubocop forbids the use of `and` and `or` in a value expression for this reason, and I believe several style guides used with Rubocop ban them entirely. I like them but have come to accept that they're more trouble than they're worth (in a shared codebase with lots of contributors, at least).
mberning 3y ago
If that is enough to turn you off it’s probably for the best.
matthewowen 3y ago
In python empty string is false. In ruby 0 is true. And yes, ruby has both or and || but they mean different things. I’m not saying that it isnt valid to criticize these things: first time use of a language matters, people work in multiple languages, it is good to be intuitive. But in practice, these things aren’t problems for people who work regularly in these languages, so I personally find them to be quite low salience. I recognize that this is sort of similar to the claims the hypothetical user of php makes in “php is a fractal of bad design”, but personally I find think the issues are of a different nature.
- jes5199 3y ago
  that’s not the bug here. they got caught by precedence rules
  - matthewowen 3y ago
    I suppose “|| and or” mean different things was a little too loose or broad a way of expressing that, but I agree what the big is and you see how it fits in with my overall point I’m sure
  - sinkwool 3y ago
    I believe what GP is saying is: coming from python, which uses `and` and `not` and `or` you expect those to be the binary operators in ruby as well. You are then surprised when they behave unexpectedly. Who is then to blame for your frustration? Is ruby a bad language for having both `and` and `&&`, or are you at fault for not doing enough research? (I don't see why someone coming from python would look any further after trying `and` and seeing that it seems to work just fine). I think this is an unfortunate situation, but one that doesn't really happen to someone that does ruby day-to-day; so it shouldn't really factor in as an argument to write ruby off. But then is being surprised by `["0","1","10"].map(parseInt) // => [0, NaN, 2]` in JavaScript a sign of bad language design or does it just mean that you don't have enough experience with the language yet?
avg_dev 3y ago
yes, that does seem pretty annoying. however, irb(main):001:0> value = false or true => true irb(main):002:0> value => false irb(main):003:0> value = false || true => true irb(main):004:0> value => true irb(main):005:0> I believe if you use the `||` operator instead of `or`, then things just work out fine. I agree it is really annoying. But I am pretty sure if you use a tool like RuboCop https://github.com/rubocop/rubocop https://github.com/rubocop/rubocop (a static code analysis tool) then it will catch bugs like this. Note that I am not recommending Ruby. But in my experience if I want to work with a language and it has a community style guide and a linter that enforces it, it will save me some heartache. Just editing to add this reference: https://rubystyle.guide/#and-or-flow https://rubystyle.guide/#and-or-flow

jameskilton 3y ago

You want to use "||" like most languages, not "or". They have different precedence rules.

sinkwool 3y ago

`and`, `or`, `not` have much lower precedence than `&&`, `||` and `!` . I would just avoid `and` and `or` in general. For some more explanation see https://graceful.dev/courses/the-freebies/modules/ruby-language/topic/episode-125-and-or/ https://graceful.dev/courses/the-freebies/modules/ruby-langu...

djur 3y ago
Rubocop forbids the use of `and` and `or` in a value expression for this reason, and I believe several style guides used with Rubocop ban them entirely. I like them but have come to accept that they're more trouble than they're worth (in a shared codebase with lots of contributors, at least).

mberning 3y ago

If that is enough to turn you off it’s probably for the best.

matthewowen 3y ago

In python empty string is false. In ruby 0 is true. And yes, ruby has both or and || but they mean different things. I’m not saying that it isnt valid to criticize these things: first time use of a language matters, people work in multiple languages, it is good to be intuitive. But in practice, these things aren’t problems for people who work regularly in these languages, so I personally find them to be quite low salience. I recognize that this is sort of similar to the claims the hypothetical user of php makes in “php is a fractal of bad design”, but personally I find think the issues are of a different nature.

jes5199 3y ago
that’s not the bug here. they got caught by precedence rules
- matthewowen 3y ago
  I suppose “|| and or” mean different things was a little too loose or broad a way of expressing that, but I agree what the big is and you see how it fits in with my overall point I’m sure
- sinkwool 3y ago
  I believe what GP is saying is: coming from python, which uses `and` and `not` and `or` you expect those to be the binary operators in ruby as well. You are then surprised when they behave unexpectedly. Who is then to blame for your frustration? Is ruby a bad language for having both `and` and `&&`, or are you at fault for not doing enough research? (I don't see why someone coming from python would look any further after trying `and` and seeing that it seems to work just fine). I think this is an unfortunate situation, but one that doesn't really happen to someone that does ruby day-to-day; so it shouldn't really factor in as an argument to write ruby off. But then is being surprised by `["0","1","10"].map(parseInt) // => [0, NaN, 2]` in JavaScript a sign of bad language design or does it just mean that you don't have enough experience with the language yet?

avg_dev 3y ago

yes, that does seem pretty annoying. however, irb(main):001:0> value = false or true => true irb(main):002:0> value => false irb(main):003:0> value = false || true => true irb(main):004:0> value => true irb(main):005:0> I believe if you use the `||` operator instead of `or`, then things just work out fine. I agree it is really annoying. But I am pretty sure if you use a tool like RuboCop https://github.com/rubocop/rubocop https://github.com/rubocop/rubocop (a static code analysis tool) then it will catch bugs like this. Note that I am not recommending Ruby. But in my experience if I want to work with a language and it has a community style guide and a linter that enforces it, it will save me some heartache. Just editing to add this reference: https://rubystyle.guide/#and-or-flow https://rubystyle.guide/#and-or-flow