Strange behavior of the subtraction operator

[piouPiouM]

I noticed the - operator needs to be wrapped by spaces in order to work as intented. Operation 1-1 for example, will return a list and not 0.

What is the origin of this unexpected behavior?

Thx.

Some examples:

$ sass -v
Sass 3.3.0.alpha.184 (Bleeding Edge)
$ sass -i
>> 1 - 1 // returns a number
0
>> 1- 1 // returns a number
0
>> 1 -1  // returns a list and not a number
(1 -1)
>> 1-1  // returns a list and not a number
(1 -1)
>> a-b
"a-b"
>> b-a
"b-a"
>> a-2 // returns a string as expected
"a-2"
>> 1-b // returns a list and not a string
(1 "-b")

[KittyGiraudel]

This is probably due to the fact - is used as both a hyphenation mark and a substraction operator. In order to differenciate the two, I believe the operator needs to be wrapped by spaces.

I'd love to hear a word of Nathan / Chris on this though. :)

[nex3]

This is expected behavior, although unfortunately kind of unintuitive at the margins. In Sass, - can be part of an identifier, part of a negative number, a binary subtraction operator, or a unary negation operator. Being an identifier/number has the highest precedence; unary negation has the lowest. This gives rise to all the cases you listed. Let's go over them one by one:

In 1 - 1 it's unambiguously subtraction. Easy peasy. 1- 1 is the same; since 1- isn't a valid number, the - must be the subtraction operator.

1 -1 starts to get tricky. -1 is parsed as a number before Sass ever starts to look for operators. This follows the CSS grammar. 1-1 is parsed the same way.

a-b is a valid CSS identifier, so it's parsed as an unquoted string. Same for b-a and a-2.

1-b is similar to the 1 -1 case; -b is a valid identifier, so it gets parsed as that before any operators are parsed.

[KittyGiraudel]

Thanks for detailed explanations Nathan.

[piouPiouM]

Thx for taking the time to explain it so clearly Nathan!