Re: New JVM instruction invokedynamic
On Sun, 14 Nov 2010, Ken Wesson wrote:
On Sat, 13 Nov 2010 16:07:49 +0100, M.O.B. i L. wrote:
I read this article:
<http://java.sun.com/developer/technicalArticles/DynTypeLang/
index.html>.
It's about the new JVM instruction invokedynamic that should make
dynamic languages faster.
Remind me: what does invokedynamic do differently from invokevirtual?
Everything.
It's not just a slightly looser version of invokevirtual which lets you be
a bit more vague about types in the bytecode. It involves a completely
new, and frankly batshit insane, calling process, which involves finding
and using things called MethodHandles, which are objects, but which can
get involved with the call process.
Bear in mind that dynamic languages (here i will use a dynamic version of
java i have just made up) don't just need to be able to do:
var foo = 23;
foo.toString(); // foo has no static type here
They need to be able to do:
var foo = 23;
foo.toQuotedString = do String() {return "'" + this.toString() + "'"'}; // made-up lambda syntax
foo.toQuotedString(); // that method didn't even exist a minute ago
Supporting that inside the JVM requires some serious voodoo. invokedynamic
is it.
tom
--
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