On Aug 17, 2007, at 2:47 PM, Garrett Smith wrote: > It would be nice to have Array literal syntax declare it's ArrayType > before the declaration of the array. > > For example: > > 1. var x : Array<String> = [ "foo", "bar", document.title, > getAnotherString() ];
Array is not a parameterized type. If it were, the syntax would be Array.<T>. Array must be backward compatible, so if it were changed to be parameterized by element type, then it would have to default to Array.<*> when used without a parameter list. But we don't have default type parameters, and anyway a type-parametric Array reference without the actual type param list would be ambiguous: should it mean Array.<*> by default, or Array, with instantiation using an actual type param happening later: let A = Array; type TA = A.<T> ? So there's no good way to overload Array as you want. Also, Array is closer to Object than to any homogenous tuple or vector type. Hence the separate http://wiki.ecmascript.org/doku.php?id=proposals:arrays http://wiki.ecmascript.org/doku.php?id=proposals:vector proposals. > 2. var x = [ "foo", "bar", document.title, getAnotherString() ] : > String; > > example 1 is more clear to read because in a long array, you'd see > right away what type of Array it is. Please see the above proposals and the prior proposals: http://wiki.ecmascript.org/doku.php?id=spec:type_system http://wiki.ecmascript.org/doku.php?id=spec:type_relations > Is the former syntax (or some variant thereof) going to be available? No, as explained above. But what you might want is: let x : [string] = ["foo", "bar", document.title, getAnotherString()]; Notes: * let trumps var in any hand ;-) * string is the type of "foo", String is the dynamic class for wrappers, as in ES1-3 that shares its .prototype with string instances as well as String instances, via the usual prototype-based delegation. Prefer string in general. * [string] is a type expression denoted a structural array type. > What about for Objects? See structural object types. /be _______________________________________________ Es4-discuss mailing list Es4-discuss@mozilla.org https://mail.mozilla.org/listinfo/es4-discuss
