Question

In a talk at QCon London 2009, the inventor of this concept noted how his friend Edsger Dijkstra disapproved of it and compared its use to a situation where “every bachelor [is] married (15[1])polyamorously to the same person”. In C, the stddef.h (“S-T-D def dot h”) header contains two macros, one defining the “offset of” function and the other defining this concept. The most (15[1])popular languages that avoid this concept are (15[1])Rust and Swift; as an alternative, Rust instead uses an “Option” enum. (15[1])Tony Hoare, who invented this concept when designing ALGOL W, has called it a (*) “billion dollar mistake”. This concept names probably the most common Java runtime exception, which can occur if you call a method of an uninitialized object. In C, these things can be generated with the expression “(void*) 0” (“void star zero”). For 10 points, name this kind of reference that points to nothing. ■END■ (10[1])

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