Re: Some advice on a "simple" thing...

Some clarificaation…. a while back you helped me write a testing framework…here is the code:
get_all_tests(Tests) :-
	setof(Line-Name, get_one_test(Name, Line), Tests).


get_one_test(Name, Line) :-
	current_predicate(Name/0),
	atom_concat('test_', _, Name),
	predicate_property(Name, prolog_line(Line)).	
It uses ‘pairs’ as I understand them, using the ‘-‘ to combine the key and value, so in your response, what is ‘=‘ doing in this context in the list of flags????

Just when I thouthgh I was beginning to understand! LMAO

Thanks once again,

Sean.




On 9 Apr 2014, at 09:18, Daniel Diaz <[email protected]> wrote:

> Hello Sean,
> 
> you can do this with your own loop or use findall like this:
> 
> flag(public, 0x0001).
> flag(final, 0x0010).
> flag(super, 0x0020).
> flag(interface, 0x0200).
> flag(abstract, 0x0400).
> flag(synthetic, 0x1000).
> flag(annotation, 0x2000).
> flag(enum, 0x4000).
> 
> 
> get_java_flags(Value, Flags) :-
>     findall(Name, has_flag(Value, Name), Flags).
> 
> 
> has_flag(Value, Name) :-
>     flag(Name, Mask),
>     Value /\ Mask =\= 0.
> 
> 
> then call it with:
> 
> | ?- get_java_flags(0x421, Flags).
> 
> Flags = [public,super,abstract]
> 
> I have detailed a bit to be more comprehensive: the has_flag/2 predicate could be inlined inside the findall surrounding with ().
> 
> If you prefer to have the flags as a parameter pass them as a list and use member to handle backtracking (done by get_flags/3 here):
> 
> get_java_flags(Value, Flags) :-
>     FlagNames = [public = 0x0001,
>                 final = 0x0010,
>                 super = 0x0020,
>                 interface = 0x0200,
>                 abstract = 0x0400,
>                 synthetic = 0x1000,
>                 annotation = 0x2000,
>                 enum = 0x4000],
>     get_flags(FlagNames, Value, Flags).
> 
> 
> 
> get_flags(FlagNames, Value, Flags) :-
>     findall(Name, has_flag(FlagNames, Value, Name), Flags).
> 
> has_flag(NameFlags, Value, Name) :-
>     member(Name=Mask, NameFlags),
>     Value /\ Mask =\= 0.
> 
> 
> Daniel
> 
> Le 09/04/2014 01:02, Sean Charles a écrit :
>> Hello list,
>> 
>> I have almost completed a predicate called ‘jread’ which parses a Java .class file into a term that will allow me to create a database of all of the methods, fields, superclass and interfaces for that class and ultimately create a database for a complete “android.jar” file of any required API level.
>> 
>> I am, for educational purposes and my own learning, trying to build a system like Hoogle/Hayoo for Android. I do a lot of Android and I wanted to create a sytem I can wire into Emacs/IntelliJ or anything for that matter, a simple HTTP server that can supply a list of methods that have a certain type signature using a si mple query language.  Searching by types it very very useful when using Haskell and I wanted to improve my Prolog so I figured why not do something like that in GNU Prolog? I have already started a simple HTTP library in pure GNU Prolog as well but this comes first now.
>> 
>> Progress so far is good…if I run it like this from a folder containing the unpacked android.jar file...
>> 
>> | ?- jread('javax/net/SocketFactory.class',X).
>> 
>> X = javaclass(super('java/lang/Object'),class('javax/net/SocketFactory'),implements([]),
>> methods([method(access_flags(4),name('<init>'),returns('()V'),[attr(9,
>> [0,3,0,1,0,0,0,14,42,183,0,1,187,0,2,89,18,3,183,0,4,191,0,0,0,2,0,10,0,0,0,6,0,1,0,0,0
>> ,4,0,11,0,0,0,12,0,1,0,0,0,14,0,12,0,13,0,0])]),method(access_flags(41),name(getDefault)
>> ,returns('()Ljavax/net/SocketFactory;'),attr(9,0,3,0,0,0,0,0,10,187,0,2,89,18,3,183,0,4,
>> 191,0,0,0,1,0,10,0,0,0,6,0,1,0,0,0,5])]),method(access_flags(1),name(createSocket),
>> returns('()Ljava/net/Socket;'),[attr(9,0,3,0,1,0,0,0,10,187,0,2,89,18,3,183,0,4,191,
>> 0,0,0,2,0,10,0,0,0,6,0,1,0,0,0,6,0,11,0,0,0,12,0,1,0,0,0,10,0,12,0,13,0,0]),
>> attr(18,0,1,0,19])]),method(access_flags(1025),name(createSocket),
>> returns('(Ljava/lang/String;I)Ljava/net/Socket;'),[attr(18,[0,2,0,19,0,21])]),
>> method(access_flags(1025),name(createSocket),
>> returns('(Ljava/lang/String;ILjava/net/InetAddress;I)Ljava/net/Socket;’),
>> [attr(18,[0,2,0,19,0,21])]),method(access_flags(1025),name(createSocket),
>> returns('(Ljava/net/InetAddress;I)Ljava/net/Socket;’),[attr(18[0,1,0,19])]),method(access_flags(1025),name(createSocket),
>> returns('(Ljava/net/InetAddress;ILjava/net/InetAddress;I)Ljava/net/Socket;'),[attr(18,[0,1,0,19])])])) ? 
>> 
>> The place I am at now is decoding the bit flags for the class (and eventually the methods etc) into a term.
>> 
>> A typical value would be “1057” decimal, 0x421, this contains the flags:
>> 
>> ACC_PUBLIC	0x0001	Declared public; may be accessed from outside its package.
>> ACC_FINAL	0x0010	Declared final; no subclasses allowed.
>> ACC_SUPER	0x0020	Treat superclass methods specially when invoked by the invokespecial instruction. 
>> ACC_INTERFACE	0x0200	Is an interface, not a class.
>> ACC_ABSTRACT	0x0400	Declared abstract; must not be instantiated.
>> ACC_SYNTHETIC	0x1000	Declared synthetic; not present in the source code.
>> ACC_ANNOTATION	0x2000	Declared as an annotation type.
>> ACC_ENUM	0x4000	Declared as an enum type.
>> 
>> So you can see that 0x421 means “ACC_PUBLIC, ACC_SUPER and ACC_ABSTRACT”. I would like to produce a term something like this:
>> 
>>     access_flags(public,super,abstract)
>> 
>> It’s not that I don’t know how to do it or that I can’t do it but I am not sure what is the *most elegant* way to do it in Prolog! Heaven knows I have written bit shifting loops to test for flags in a dozen languages but not in Prolog.
>> 
>> So, there’s the challenge, what is the most elegant way to turn a list of bits into a list of atom terms. Ideally I would make the list of atoms a parameter so that I can reuse it for the other flag based values.
>> 
>> Consider the gauntlet thrown!   In the meantime I am continuing to research the possibilities for myself. I will of course put it all on GitHub along with my Redis client. I may even create a Redis database with the information!
>> 
>> :)
>> Sean.
>> 
>> 
> 
> 
> -- 
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