On Sep 24, 2009, at 7:57 AM, Jason Merrill wrote:
On 09/15/2009 12:35 PM, Chris Lattner wrote:
The second major feature of Blocks vs c++ lambdas is that they can be
"copied onto the heap". This allows things like "Grand Central
Dispatch"
to work: you can write code that executes blocks asynchronously or on
other threads/work queues (after the function containing the block
has
returned). A simple example is:
void print_on_different_thread(int X) {
run_asynch(^{
printf("Hi %d\n", X);
});
}
With lambdas, the closure would be go out of scope when
print_on_different_thread returns, but blocks allows "run_asynch" to
extend the lifetime of the block.
The lambda equivalent would be
void print_on_different_thread(int X) {
run_asynch([=]{
printf("Hi %d\n", X);
});
}
since X is captured by copy, run_asynch can do whatever it wants
with the closure and not worry about the original X going away.
The only difference between blocks and lambdas here seems to be
where you decide to copy the locals off the stack.
Can the lambda (containing X) be copied and put onto a queue? What is
its type?
-Chris
