> Your comment is especially weird because you go on to discuss Lisp's approach as being "an alternative option to what Lisp does".
I assume you're talking about GP's third paragraph here. Assuming that's true, I think you've misinterpreted it: GP was talking about using infix operator notation, which is most certainly not what Lisp does.
Lisp will treat (a - b) as 5 tokens, just the same way it will treat (- a b) as 5 tokens. Infix operators are completely unrelated to this problem. What lisp is doing is determining tokens by reference to spacing (the parentheses don't need to be spaced; I believe they are reader macros but in any event they are special-cased) and then acting on the tokens. What C is doing is not that; the concept is that you eliminate all spacing before you decide what the tokens are.
So in C, there is no such thing as "a - b", only "a-b", and that's why "a-b" cannot be used as an identifier.
If you want to write your lisp in infix notation, you can, but it will remain true that (a - b) is a list with 3 elements and (a-b) is a list with 1 element, which is what matters here.
> First obvious option is to get rid of the infix "-" operator, which is what Lisp does. In lisp-like languages you don't write "a - b" instead you write "- a b", this way there is nothing to confuse "a-b" with.
> Another option is to require a space between operators. E.g. you are not allowed to write "a+b" to mean "add a to b". You have to write "a + b". This is used in Agda programming language.
is kinda not good, Lisp allows "-" in names the same reason as Agda: it tokenize by spaces (correct me if I'm wrong). This may seem as a gross error for one, and an only implied who cares error which is even true if taken word-by-word, for an other.
I assume you're talking about GP's third paragraph here. Assuming that's true, I think you've misinterpreted it: GP was talking about using infix operator notation, which is most certainly not what Lisp does.