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Tim
There are 2 possibilities about why there are so few dlls. One is
that indeed very few are written, another is that even though they
are written, they are not published or shared.
Let deal with with the first one. AFL is a powerful langauage that
there isn't a lot of things that it can't do, just look at the
userkb, the variety of tasks that afl is able to perform is quite
astounding. I once wrote an afl that calculates the trading profit
and loss for my tax return.
However there are always things that dll will do better, I
have written now over a thousand dll functions. Often a good
candidate is when afl loop is involved. The reason for that is even
though that AFL functions are optimized, ie, ref, valuewhen or cum
function are faster than if I directly write these in dll. Loops
cannot be optimized to the same extent and are generally much faster
when they are written in C++/C. Another candidate for dll is when
functions that are difficult to be achieved efficiently with AFL,
ie, you need a significant no of AFL functions to write a seemingly
simple task. Recently, I wrote myself a few functions for trading,
One of which is the WeekOfYear() function. You can do that in
with AFL alright, but the No of required previous bars makes it
unsuitalbe. With a dll, I am able to return the weekofyear value
from bar 0, but with an AFL, I have to wait til bar 20, and is too
slow to run on a tick database. Another one I wrote is what I called
HighestBefore(), that I use to find the first hour, first 30 minutes
high in a day. These are simply examples, and there are many many
more that I think have improved my ability to develop fast and
complex systems that I wouldn't want to do without.
Is dll for everybody? most definitely not, AFL, like Jscript, is a
type ignostic language, which means you dont have to tell the AFL
engine it is an integer or an array. While C++ is a strong typed
language. With AFL, most people can start coding right away without
the intrepreter telling them of the mistakes they make. On the other
hand, C++ compilers complains like a fuzzy parent about every little
thing that is not right. But it is a good thing, we all know, as any
parent would tell their kids. When the function we are trying to
write becomes complex. And dll doesn't suffer nearly as often with
obscure and intermittent errors that one encounters when one tries
to write very long and complex afls.
I disagree with those who disregard dll as little use, dll like any
tool, is only as good as the person who uses it. It is a bit like a
person who always uses his fork for his meal, complains that knife
is of little use.
The 2nd possiblity that there are so few dll is that very few are
being published or shared. I have written about that here.
http://finance.groups.yahoo.com/group/amibroker/message/125635
--- In amibroker@xxxxxxxxxxxxxxx, "Tim" <raven4ns@xxx> wrote:
>
> Hello,
> Many people have said that a DLL is the way to go for a formula.
It
> is said it is faster among other positives. Why then is there so
few
> DLL's available? I know my ignorance about computers is showing
but I
> would really like to know. Are they more complicated than an AFL,
you
> need special training, what? Thank you for indulging my curiosity.
>
> Kindest regards always,
>
> Tim
>
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