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The plus and minus operator in calc() must always be surrounded by whitespace
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https://stackoverflow.com/questions/34419813/why-must-a-or-be-surrounded-with-whitespace-from-within-the-calc-method
===> The + and - operators must always be surrounded by whitespace. 
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[question]
Why must a + or - be surrounded with whitespace from within the Calc() method?

Recently I've started using the calc(...) method within CSS. I quickly learned that code such as: width: calc(100%-2) will not work, though adding white-space before and after the - operator will fix the problem and the calc method will function properly.

After doing a bit of research I found multiple blog posts reference that the white-space is required and many have even pointed to the specification (CSS3 8.1.1) which states:

[answer]
The - character is one of the allowed characters in CSS idents. Judging by the resolution given here, it seems they wanted to prevent syntactic ambiguities that could arise from using - without whitespace, especially with keyword values such as min-content (although AFAIK keyword values aren't yet allowed within calc() — correct me if I'm wrong).
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