Ruby: Change negative number to positive number?

Question

What's the simplest way of changing a negative number to positive with ruby?

ie. Change "-300" to "300"

Solution 1

Using abs will return the absolute value of a number

-300.abs  # 300
300.abs   # 300

Solution 2

Put a negative sign in front of it.

>> --300
=> 300
>> x = -300
=> -300
>> -x
=> 300

Solution 3

Wouldn't it just be easier to multiply it by negative one?

x * -1

That way you can go back and forth.

Comments

[Sasha Chedygov]

Just note that if the number is already positive, this will make it negative.

[Brandon Bodnar]

my answer is just for negative numbers, if you need to always have the absolute value then this is definitely the better way.

[Brandon Bodnar]

Yeah. Clarified that in my comment to the above accepted answer.

[Stephen Nguyen]

its either not genius or not not madness.

[Matthias]

I like using this for clarity, as using the - sign can sometimes be easy to miss

[SRack]

Worth remembering you can use the shorthand x *= -1 if you're looking to store the new value...

[Apurva Mayank]

Based of the same principle we can even divide the any negative number by -1. However, I was just wondering what can be the benefit of using it over abs method as mentioned by Yacoby

[absynthe minded web smith]

abs returns an absolute value. If that's all you want, as the OP does, it's fine. But what if you need to go back and forth?

[Andre Figueiredo]

why negative votes? this turns negative into positive as OP asked. #abs and - are different features with same behavior for asked input/output. If that's because of an undesirable + -> -, it's no more than an assumption, since that was not covered by OP.

[Andre Figueiredo]

@ApurvaMayank what's the benefit of using abs over this? OP did not mention, but he could either turn positive to negative as well or keep it positive.. you can't assume one without that being mentioned.

[Spike0xff]

This doesn't improve on or add to the previous answers (from years ago) as far as answering the original question, which is specifically about ruby.

[Yurii Verbytskyi]

In Ruby abs and - methods are both writen in C. One of the main rules for using Ruby: don't try to invent a bicycle, rewriting native C-based methods :) Just click "Show source" to know, how wise people handled that for you) apidock.com/ruby/Integer/abs apidock.com/ruby/Integer/-

[greyoxide]

I feel like this is a good contribution, While not pinpoint specific DataCure is providing greater context as to how different languages address this issue. In fact the last example givin(c) is a great way to quickly flip the value from negative to positive and back. this could easily be written in ruby as: value * -1. Thank you DataCure, I feel like this was a good first post.