On 11/16/11 11:45 AM, Erik Arvidsson wrote:
Sorry for being too brief. Today the following works.
f();
...
function f() { ... }
but the following does not:
f();
...
let f = function f() {};
I think it is important that we keep the forward reference behavior
with classes. This requires a declarative way of defining classes.
I agree with Erik and Dave that forward references are critical for
classes. If we define syntax for classes that is less foward-reference
friendly than functions are, it will be a source of bugs (speaking from
personal experience) and be perceived as a step backward.
A declarative syntax for defining classes is the goal of the classes
proposal that *has already been accepted* into the harmony namespace
http://wiki.ecmascript.org/doku.php?id=harmony:classes
ECMAScript already has excellent features for defining abstractions
for kinds of things. The trinity of constructor functions, prototypes,
and instances are more than adequate for solving the problems that
classes solve in other languages. The intent of this strawman is not
to change those semantics. Instead, it's to provide a /terse/ and
/declarative/ surface for those semantics so that /programmer intent/
is expressed instead of the /underlying imperative machinery/.
But back to the topic of forward references, note that with today's
class pattern of defining a constructor function and then initializing
its prototype properties, we can write forward references to the
constructor, and we can often invoke the constructor through a forward
reference, but we can't invoke any methods on the initialized instances
until the prototype object is actually initialized. So forward
references are only partially possible today. A declarative class
syntax that initializes the prototype as part of the hoisting process
would be nice, though of course forward references from a prototype to
another class will be tricky.
Also, today, in the absence of modules, some programmers give up the
ability to use forward references in order to define their classes in a
private scope:
let Class = (function() { function C() {...}; C.prototype = {...};
return C; }());
I'm not familiar enough with the ES.next modules proposal to know what
impact it has on forward references...
David
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