Christopher Oliver wrote:
Sylvain Wallez wrote:Moreover, AFAIU, the "productList" variable in viewCategory() is stored in the continuation, and so if we hit "next" and then "prev", the first list exists twice (in different continuations). Isn't there a potential memory consumption problem ? I know continuations expire, but withing the expiration delay, all these lists keep floating around...
Yes, but the only things that are really duplicated are the program counter and stack frames, and even the stack itself is lazily copied. The local variables themselves (like productList) are shared between continuations.
What do you mean by "lazily copied" ? Doesn't it need to be actually copied to be stored ?
What I mean is if you have a call chain:
function f() {
g();
}function g() {
h();
}function h() {
while (true) {
sendPage(...);
}
}The call frames that represent the calls to f() and g() are shared between all continuations captured inside h(). But when a continuation escapes the while loop and returns to g(), then, at that point, a copy of the call frame of g() is made, and so on as you return up the stack.
Also, how can local variables be shared between continuations if their value changes between calls to sendPageAndWait, as is the case of producList ? Isn't it contradictory with the continuation concept which should restore variable values ?
No. That's the intended behavior - just like in Scheme. Invoking a continuation only restores the program counter. It does not roll back changes to other data. That behavior would be way too expensive! As it is the cost of invoking a continuation is negligable.
Sorry for these newbie questions. Is there any docs that explains all this ? If found your post about JavaScript for Java programmers but it doesn't give any details about this.
http://marc.theaimsgroup.com/?l=xml-cocoon-dev&m=102781075226697&w=2
Then a new fresh set are created each time.
Also, how are handled global variables ? AFAIU calling createSession() "attaches" them to the session, but what if createSession() isn't called ?
And what is the relationship between global variables and continuations ?
No special relationship: global variables are accessible in continuations as are local variables.
