Why CSS Calc() function only requires spaces before and after the "+" or "-" operator

Question

For example: calc(10px 2px); is correct but calc(10px 2px); gives an error or calc(10px - 2px); is c or rect but calc(10px -2px); gives an error or. However, this does not apply to other operations

Answer 1

For the operator, the operation may be slightly more complicated than calc(10px 2px);. I mean something like calc(5px -1px); is actually more complex and impossible to be calc(5px -1px);.

For the - operator, how does CSS know whether - is the minus operator or part of a negative number? I mean logically.

Additionally, whitespace makes code easier for humans to read.

Learn more about CSS calc() function in the documentation.