Create em converter function in SASS not SCSS - sass

Question

I am new to SASS and Compass trying to create one function which can convert passed pixel value to em. I found one tutorial but it is for SCSS and that doesn't work with SASS.
Even I have checked on SASS website but seem they have most document for SCSS and not everything they have describe for SASS.
Here what I am writing
#function em($px, $base: 24px)
#return ($px / $base) * 1em
Also using vertical-rythem in my project and tried this to but than again giving error for $base-font-size
#function em($px, $base: $base-font-size)
#return ($px / $base) * 1em
So when I use it as
font-size: em(16px)
It should convert to 1em in output

Answer 1

The function you have seems correct. Just make sure you have defined $base-font-size with a value such as 16px.
The above mixin you have should also work
$base-font-size: 16px;
#function em($px, $base: $base-font-size) {
#return ($px / $base ) * 1em;
}
Now you can call font-size: em(16px); and it should work
You can also call this function with an optional base, sometimes you might want to calculate on a base that's not 16px.
Please also look up http://css-tricks.com/snippets/css/less-mixin-for-rem-font-sizing/ for rem font sizing. You might want to skip em because they have a nesting problem http://css-tricks.com/why-ems/
For a more detailed version of the above mixin, where you can call
border: emCalc (10 20 30 40);
Where you don't have to repeat the px value again and again and you may have 1 to 4 values within, check the mixin in Zurb's foundation _global.scss
https://github.com/zurb/foundation/blob/master/scss/foundation/components/_global.scss#L183