This is just guesswork on my part, but: 1. It’s hard to implement this in a single-pass compiler Lua’s bytecode compiler is implemented as a single-pass recursive descent parser that immediately generates code. It does not parse to a separate AST structure and then in a second pass convert that to bytecode. This forces some … Read more
Because interfaces specify only what the class is doing, not how it is doing it. The problem with multiple inheritance is that two classes may define different ways of doing the same thing, and the subclass can’t choose which one to pick.
In Lua 5.2 the best workaround is to use goto: This is supported in LuaJIT since version 2.0.1
EDIT: Indeed there was a patch which included sign() in math, but it wasn’t accepted, because they didn’t agree on what it should return in all the edge cases (+/-0, +/-nan, etc) So they decided to implement only copysign, which (although more verbose) can be used to delegate to the end user the desired behavior for edge cases – which sometimes might require the call … Read more