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

ie. Change "-300" to "300"

Shpigford
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4 Answers4

304

Using abs will return the absolute value of a number

-300.abs  # 300
300.abs   # 300
Yacoby
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    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 Mar 19 '10 at 22:41
31

Put a negative sign in front of it.

>> --300
=> 300
>> x = -300
=> -300
>> -x
=> 300
Brandon Bodnar
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20

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

x * -1

That way you can go back and forth.

Blubber
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absynthe minded web smith
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  • I like using this for clarity, as using the - sign can sometimes be easy to miss – Matthias Feb 12 '16 at 10:21
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    Worth remembering you can use the shorthand `x *= -1` if you're looking to store the new value... – SRack Oct 24 '16 at 15:33
  • 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 – Apurva Mayank Mar 20 '18 at 02:55
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    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? – absynthe minded web smith Mar 21 '18 at 03:45
  • @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. – Andre Figueiredo Feb 14 '20 at 19:35
0

Most programming languages have the ABS method, however there are some that do not Whilst I have not used Ruby before, I am familiar its a framework that runs on PHP

The abs method is available on PHP https://www.php.net/manual/en/function.abs.php

With Ruby the syntax appears slightly different is integer.abs https://www.geeksforgeeks.org/ruby-integer-abs-function-with-example/

But for future reference the abs method is really small to code your self.

here is how in a few different languages:

JavaScript:

function my_abs(integer){
    if (integer < 0){
        return integer * -1;
    }
    return interger;
}

Python:

    def my_abs(integer):
    if (integer < 0):
        return integer * -1
    return integer

c:

int my_abs(int integer){
    if (interger < 0){
        return integer * -1;
    }
    return integer;
}

This means should you ever find yourself with a programming language that doesnt have a built in abs method, you know how to code your own its just simply multiply any negative number by -1 as you would of gathered in my examples

DataCure
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    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. – Spike0xff Mar 18 '21 at 17:29
  • 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) https://apidock.com/ruby/Integer/abs https://apidock.com/ruby/Integer/- – Yurii Verbytskyi Mar 18 '21 at 19:18
  • 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. – greyoxide Mar 18 '21 at 20:30