It's complex because it's powerful. ~A is the most common directive; it simply prints an object. '~{...~}' (braces) iterates over a list, applying the directives within it to the list elements. Within that construct, '~^' exits if the last element of the list has been consumed; it's used here to keep the separating space from being printed after the last element. '~@(...~)' (parens) capitalizes words in the output of the directives it contains, downcasing the non-initial character of each word.

So there's a lot more power here than in 'printf' control strings. If you find the more exotic notation unintuitive -- and you certainly wouldn't be alone -- you don't have to use it.

I am only recently a lisp user but honestly, how is the format function far from:

printf("something %s then %d finally %f!", "asd", 1, 1.2)

As mentioned, there is a loop built into format. Since lisp also has a (list) function eg: (list 'a 'b 'c 1) I still don't see an argument beyond familiarity with the C style printf syntax for why format is bad/unreadable.

I do not understant it, but with changing ~ with % I can imagine what it does.