Sass negative variable value?

Question

I have a couple of scss selectors where I use the same amount positive and negative, as in:

padding: 0 15px 15px;
margin: 0 -15px 20px -15px;

I'd prefer to use a variable for all the 15px amounts, but this does not work:

$pad: 15px;
padding: 0 $pad $pad;
margin: 0 -$pad 20px -$pad;

The margin amounts convert to positive numbers. Am I missing something?

score 243 · Answer 1 · answered Nov 08 '12 at 19:44

243

Try it like this

margin: 0 (-$pad) 20px (-$pad);

answered Nov 08 '12 at 19:44

Zoltan Toth

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Automatically tried this approach - seems not to be working when using in calc function. Edit: Seems like you don't need to use parentheses when using calc, but you do need to interpolate http://stackoverflow.com/questions/17982111/sass-variable-in-css-calc-function – Kevin Mar 20 '17 at 15:38

Vangel Tzo · Answer 2 · 2018-11-30T10:02:40.913

48

A more sane solution according to sass guidelines would be to interpolate variables like the following example:

margin: 0 -#{$pad} 20px -#{$pad};

An example: https://www.sassmeister.com/gist/c9c0208ada0eb1fdd63ae47830917293

edited Nov 30 '18 at 10:02

answered Dec 27 '17 at 10:41

Vangel Tzo

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@Green You can always check the example link: https://www.sassmeister.com/gist/c9c0208ada0eb1fdd63ae47830917293 – Vangel Tzo Oct 21 '19 at 20:28
This is better than the accepted answer because it works when using a mixin inside it also :) – OZZIE Sep 15 '21 at 10:20

score 7 · Answer 3 · answered Jan 08 '20 at 11:58

7

I'm adding my two-penneth after considering the two previous answers, but then reading this (emphasis mine):

You should especially avoid using interpolation like #{$number}px. This doesn’t actually create a number! It creates an unquoted string that looks like a number, but won’t work with any number operations or functions. Try to make your math unit-clean so that $number already has the unit px, or write $number * 1px.

Source

Therefore I believe the correct way would be as follows, which preserves the mathematical abilities of SASS/SCSS:

$pad: 15px;
padding: 0 $pad $pad;
margin: 0 $pad*-1 20px $pad*-1;

answered Jan 08 '20 at 11:58

EvilDr

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At first glance, it seems to be nit-picking (your answer), but on second glance it really is the better answer. After all, if the variable does become a negative variable the answer becomes positive! $pad: -2rem; ... margin: 0 -#{$pad}; // becomes margin: 0 --2rem; margin: 0 $pad*-1; // becomes margin: 0 2rem; – Fnordius Jun 23 '20 at 14:47
this is a novel solution but I disagree that it's the "correct" way - do you think it's even better than this similar solution? `margin: 0 0 - $pad 20px 0 - $pad;` – Jon z Mar 09 '22 at 15:13

score 2 · Accepted Answer · answered Jun 09 '21 at 14:49

2

create a function

@function neg($val) {
  @return $val * -1
};

then I use it like this

$gutter: 30px;

.header {
  margin: $gutter neg($gutter);
}

answered Jun 09 '21 at 14:49

Bouh

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score 1 · Answer 5 · answered Mar 09 '22 at 15:12

The official sass guides suggest a similar solution to the (currently) highest voted answer - instead of wrapping the minus-sign inside the parens, put it outside, e.g.

$pad: 15px;
padding: 0 $pad $pad;
margin: 0 -($pad) 20px -($pad);

source: https://sass-lang.com/documentation/operators/numeric#unary-operators

and per #comment-72915126 you would want to interpolate the sass value when it appears inside a css calc function:

margin: calc(#{-$pad} - 10px);

strangely, the parens are no longer required - perhaps the string interpolation acts in a similar way to wrapping it in parens?

(I'm using prettier@2.3 and dart-sass@1.49)

Sass negative variable value?

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