A use of existential types that I’ve run into is with my code for mediating a game of Clue. My mediation code sort of acts like a dealer. It doesn’t care what the types of the players are – all it cares about is that all the players implement the hooks given in the Player … Read more
First of all, take a look at the “Curry Howard correspondence” which states that the types in a computer program correspond to formulas in intuitionistic logic. Intuitionistic logic is just like the “regular” logic you learned in school but without the law of the excluded middle or double negation elimination: Not an axiom: P ⇔ … Read more
The first one matches a single whitespace, whereas the second one matches one or many whitespaces. They’re the so-called regular expression quantifiers, and they perform matches like this (taken from the documentation): Greedy quantifiers X? X, once or not at all X* X, zero or more times X+ X, one or more times X{n} X, … Read more