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I agree that Mike's comments were quite good.
The only difference in opinion is that I would call use "public static" everywhere
instead of two different "global static" and "public static". In AFL there is no need to differentiate declaration vs definition.
Less confusion and less error prone. Still I like simplicity and quickness of "shared" (or maybe "public" alone?)
What I don't like with this approach is that having such simple keyword will make it way too easy for people
to declare everything as public and then cry to support that they run out of memory.
The original poster as well as others simply forgot the key difference between AFL and other languages.
The fact that simple variable in AFL can be ARRAY and in extreme cases such array can have megabyte size.
Encouraging abuse of static/shared variables by making it too simple and no-brainer, would result in
people complaining that they run out of memory.
Try using hundreds of things like
static float x[ 10000000 ];
in C/C++ and you will see what I mean.
There is really huge difference between having 100 static numbers (scalars) and 100 static arrays.
That was also one of the reasons why initially static arrays were not available in AB.
As soon as I implemented it, I have seen people coming to support with complaints that
they have created zillions of static arrays and they have problems (out of mem).
If these keywords were implemented, there would be strong need to build in safety measures to protect
AmiBroker from abusing such functionality by using 100s of array static vars.
Best regards,
Tomasz Janeczko
amibroker.com
----- Original Message -----
From: "progster01" <progster@xxxxxxxxxxxxxxxxxx>
To: <amibroker@xxxxxxxxxxxxxxx>
Sent: Friday, November 06, 2009 6:37 PM
Subject: [amibroker] Re: Biggest shortcoming of AFL scripting language
> Mike,
>
> Very thoughtful commentary you've made, there's alot to agree with there (even for those coming from C++ rather than Java).
>
> IMO, all the types of locality specifiers have their uses. Having a few more of them at our disposal would be great (carefully
> chosen by TJ to integrate well, of course!).
>
> - Progster
>
>
> --- In amibroker@xxxxxxxxxxxxxxx, "Mike" <sfclimbers@xxx> wrote:
>>
>> I'd like to address what I see as a flaw in the logic of the original post, as well as a suggestion to Tomasz's reply.
>>
>> There are perhaps more Java developers now than C++ developers. For the true equivalent of StaticVarGet/Set, the Java keyword
>> "public" would work very nicely (as opposed to "shared").
>>
>> e.g. Java
>>
>> class MyClass {
>> public static int a;
>> ...
>> }
>>
>> e.g. AFL
>>
>> public static a;
>>
>> In Java, the variable "a" would be accessible as is (i.e. just by typing "a") anywhere within its own class definition (i.e. the
>> file), and in qualified form outside of its class (e.g. MyClass.a).
>>
>> As Tomasz pointed out, the AFL declaration would be global and therefore have no equivalent qualifier (i.e. no MyClass
>> qualifier). I believe that that is what would be the biggest source of confusion with what the original poster suggested.
>>
>> Consider that:
>>
>> - In Java, when we write MyClass.a from within MyOtherClass, it is clear that the static variable is coming from somewhere else
>> (i.e. from the file MyClass.java).
>>
>> - Similarly, using AFL's function call StaticVarGet, in a different file, makes it clear that the variable is not necessarily
>> local to the current file.
>>
>> Compare the above to the original poster's proposal of just using
>>
>> "a = 3" or "a"
>>
>> When "a" is referenced outside of the file that it was declared in, the variable becomes ambiguous. Should it default to a new
>> implicit, non static variable as is the current behavior? Or, should it first try to resolve against a static variable of that
>> name? What happens when the user has set the option to force all variables to be explicitly declared; Must the author redeclare
>> the static in every file that its referenced? Clearly, the proposal as originally suggested is not sufficient.
>>
>> However, this weaknesses might be addressed by requiring the use of the existing "global" keyword whenever a static is to be
>> referenced outside of the file in which it was declared.
>>
>> e.g.
>>
>> File1.afl
>> public static a; // Declared in File1.afl
>> a = 3;
>>
>> File2.afl
>> global static a; // Treat as having been declared somewhere else
>> x = a;
>>
>> This has the advantage of building upon the semantics of the existing "global" keyword, while at the same time being compatible
>> with the requirement of explicit variable declarations.
>>
>> Going a step further, what I would really like to see is the introduction of both "static" and "final" such that we can write our
>> own procedures/functions that accept constants just as AmiBroker itself has constants for atcFlagDefaults, etc.
>>
>> e.g.
>>
>> File1.afl
>> public static final myInterestingValue = 0;
>> public static final myOtherValue = 2;
>>
>> procedure doSomething(value) {
>> switch (value) {
>> case myInterestingValue: ...
>> case myOtherValue: ...
>> }
>> }
>>
>> File2.afl
>> #include_once <File1.afl>
>> ...
>> doSomething(myInterestingValue);
>>
>>
>> We can do this now already. But, we have no way to protect against anyone accidentally changing the value of myInterestingValue,
>> myOtherValue.
>>
>> These two keywords would go a long way towards promoting more modular code in larger coding projects.
>>
>> Mike
>>
>
>
>
>
> ------------------------------------
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