Don Wrote: > This is for me the last remaining D2 issue. > I've mentioned this several times before. Mutable array 'literals' are > wrong on so many levels. Here are some of the issues, listed in > decreasing importance. > > (1) The language has no syntax for immutable array literals. > [1,2,3] is mutable. You can created an immutable literal using the > awful 'static const' syntax, but that only works for named literals. > > (2) Concurrency issues make (1) even more important. It ought to > possible to pass an array (defined at compile time) as a message. > > (3) Performance of the existing array 'literals' is absolutely > appalling. I doubled the speed of my entire app by changing ONE array > declaration from 'immutable [] xxx' into 'static const [] xxx'!!! > Right now, if an array literal appears in your code, chances are it's a > performance bug. It's deceptive that there's a hidden heap allocation > happening in every array literal. It's got no business being in a > systems language IMHO. > > (4) It is unintuitive. "hello" is immutable, but ['h','e','l','l','o'] > is not??? > > (5) It's trivial (a one-liner) to make a function to create a mutable > array literal. We don't need it in the language. > > Mutable arrays literals are common in toy examples, but they've got very > little real-world relevance. By contrast, immutable array literals are > used in lookup tables all the time. They are extremely common. We need > to be able to express them. > > This is the only remaining thing in D2 which I'm certain is a big > mistake. Of course there's ugliness in various places, but it's possible > to ignore them or work around them. This is a primitive, > bread-and-butter issue with no workaround.
I agree. This has caused huge performance problems that were fixed by changing all my 'immutable x = []' to 'static immutable x = []'. Can we keep the current behaviour for when some of the values are not known at compile time? I know it's just sugar but it's very sweet. eg. auto y = [1, 2, x, y];
