Standards or not?

[Semigradsky]

Now this library reducing correct calc expressions.

For some people it would be convenient to write shorter but incorrect calc expressions.
For example

div {
  margin-left: -calc(2px *2);
}

instead

div {
  margin-left: calc(-1*(2px * 2));
}

There are some issues about this: #30, #32

I think that we should decide: use ONLY the correct syntax or start supporting an informal syntax.
If we choose the second option, we need to agree on what it will be.

[MoOx]

I would go for spec only but I don't really use this package neither postcss this day so do whatever you feel is good.