Bug 8864 – Simpler syntax for array literal of structs from one argument

I'd like to write code like this (the constructors of the structs must take 1 argument), because it's quite handy in many situations: // some imports here void main() { BigInt[] data1 = [5, 6, 9]; Ranged!(int,5,10)[] data2 = [5, 6, 9]; Nibble[] data3 = [1, 2, 15]; // Nibble.sizeof == 1 alias Typedef!int Mint; Mint[] data4 = [5, 6, 9]; } Currently in D you write this, it's not handy if you have many items: // some imports here void main() { auto data1 = [BigInt(5), BigInt(6), BigInt(9)]; alias Ranged!(int,5,10) R; // a short name auto data2 = [R(5), R(6), R(9)]; auto data3 = [Nibble(1), Nibble(2), Nibble(15)]; alias Typedef!int Mint; Mint[] data4 = [Mint(5), Mint(6), Mint(9)]; } Or you duplicate the arrays: import std.bigint; void main() { auto aux = [5, 6, 9]; auto data1 = new BigInt[aux.length]; foreach (i, a; aux) data1[i] = BigInt(a); // ... } A simpler example: struct Nibble { ubyte u; this(ubyte ub) in { assert(ub < 16); } body { this.u = ub; } } void main() { Nibble[] data = [5, 6]; } You currently write: struct Nibble { ubyte u; this(ubyte ub) in { assert(ub < 16); } body { this.u = ub; } } void main() { auto data = [Nibble(5), Nibble(6)]; } Scala accepts a similar syntax (Scala here probably uses a more general feature named implicits): // Scala code object Main extends App { val data : Array[BigInt] = Array(10, 20, 30) } See also the discussion thread: http://forum.dlang.org/thread/[email protected]

It's meant to work with 2D arrays too: struct Nibble { ubyte u; this(ubyte ub) in { assert(ub < 16); } body { this.u = ub; } } void main() { Nibble[][] data = [[1, 2], [3, 4]]; }

Today following style initializing is properly allwed: struct S { this(int n) {} } S s = 1; // translated to: T t = T(1); As a natural conclusion, following syntax should also be accepted IMO. S[] a = [1, 2, 3]; // For each ArrayInitializer elements, implicit struct // constructor call of type S should be considered. Then it could be translated to: S[] a = [S(1), S(2), S(3)];

*** Issue 7255 has been marked as a duplicate of this issue. ***

This is a core language change with many risks associated. A DIP would need to discuss them all. Workarounds are possible with library code: void main() { BigInt[] data1 = makeArray!BigInt(5, 6, 9); Ranged!(int,5,10)[] data2 = makeArray!(Ranged!(int,5,10))(5, 6, 9); Nibble[] data3 = makeArray!Nibble[1, 2, 15]; // Nibble.sizeof == 1 alias Typedef!int Mint; Mint[] data4 = makeArray!Mint(5, 6, 9); } Within the current language this is possible although not super handy: BigInt[] data1 = only(5, 6, 9).map!(x => BigInt(x)).array;