~ sign function in lukasiewicz logic [closed]
In the book, "Soft Computing and its Applications in Business and Economics", by R. R. Aliev and Rafig Aliyev, what does the tilde sign mean in the following equation?
$$(\sim (P ≈ \Rightarrow Q))$$
I know how to solve inside, but couldn't find the function of the tilde.
Tilde is used for negation in other texts, e.g. here: plato.stanford.edu/entries/lukasiewicz/polish-notation.html
It is also listed as a negation operator on page 219 of the cited text.