在 Sun, 19 Apr 2009 02:16:30 +0800，Andrei Alexandrescu
<seewebsiteforem...@erdani.org> 写道:
bearophile wrote:
Andrei Alexandrescu:
Yes. The amount of confusion in this thread is staggering.
I think I have misunderstood about the whole thread then. If the
string isn't determined at run time, then this thing isn't useful for
my purposes, and it's not close to the object-C as I was talking about,
and it's not similar to __getattr__ of Python, etc.
Bye,
bearophile
In the syntax
a.b
how would either of a and b be identified at runtime? I mean, you write
the code somewhere and it gets compiled. It's not like you're reading
"a.b" from the console and then call some eval() function against them.
Depends on the compiler semantic. The compiler can feed the opDot with the
variable b if it's a string. The compiler can intepret the opDot that way.
Consider:
string b = "myfunction";
dynamo.b(1);
we can translate this to dynamo.opDot("b",1); and we can also rewrite this
to dynamo.opDot(b, 1);( if there's a non-template version of opDot just
like the current one I have) and even more we can let the compiler decide
which rewrite version it prefers, because compiler can simply firstly try
to query if there's a variable named b with type of string in the scope of
caller. There's someone posted this sort of dynamic language semantic, and
I was astonished and thought it were impossible under the opDot scheme.
Yet till now, I finally realize that the compiler gets all source input
just as the dynamic language interpreter gets input from a console. There
won't be much barrier blocking us from mocking every dynamic features.
Just we need to be careful to choose some useful part and equip our static
land without much potential risk while developer friendly interface.
I have not and don't intend to choose the second rewrite version. Whether
we should go the second version is left for more discussion. I think many
static language developers won't enjoy the second rewrite version at the
first glance. I didn't like it either. Yet, after consider a little bit
longer, I start to think it might not be as that bad as the first
imagination impression in our own mind.
It can be funny to have some code like:
string doSomething;
if (animal = "dog") doSomething="bark";
if (animal = "human") doSomething="talk";
dynamo_animal.doSomething();
Ok, this may look pretty evil in a static language for many among us. I
need to claify that I don't intend to go into that direction till further
discussion will be made.
The first rewrite version and revised by your template suggestion should
be able to do the __getattr__ trick, if I get the idea of __getattr__
correctly. I think bearophile's worry can be alleviated. ;)
Andrei
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