Re: Accessing PowerLoom from Haskell

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Hans,
Thanks for the very nice example. Thanks to it I manage to call PowerLoom from Haskell over C.

I have attached a file with the Haskell version of "powerloom-from-c.c", powerloom-from-haskell.hs


Compile and run like this:                                                   
                                                                              
$ export PL_HOME=.../powerloom-4.0.0.beta                             
$ g++ -I$PL_HOME/native/cpp -I$PL_HOME/native/cpp/stella/cpp-lib/gc/include -c pli-c-api.cc -DSTELLA_USE_GC
$ ghc -c powerloom-from-haskell.hs                                             
$ ghc pli-c-api.o powerloom-from-haskell.o -o powerloom-from-haskell -L$PL_HOME/native/cpp/lib -lpowerloom -lpowerloom-extensions -lutilities -llogic -lstella -lgc -lm -lstdc++
$ export LD_LIBRARY_PATH=$PL_HOME/native/cpp/lib                               
$ ./powerloom-from-haskell                                                     


Sincerely
Anders



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{-# LANGUAGE ForeignFunctionInterface #-}

-------------------------------------------------------------------------=
------
-- Compile and run like this:
--
-- export PL_HOME=3D.../powerloom-4.0.0.beta
-- g++ -I$PL_HOME/native/cpp -I$PL_HOME/native/cpp/stella/cpp-lib/gc/incl=
ude -c pli-c-api.cc -DSTELLA_USE_GC
-- ghc -c powerloom-from-haskell.hs
-- ghc pli-c-api.o powerloom-from-haskell.o -o powerloom-from-haskell -L$=
PL_HOME/native/cpp/lib -lpowerloom -lpowerloom-extensions -lutilities -ll=
ogic -lstella -lgc -lm -lstdc++
-- export LD_LIBRARY_PATH=3D$PL_HOME/native/cpp/lib
-- ./powerloom-from-haskell
--
{-
Initializing...
(defconcept person)
/PL-KERNEL-KB/PL-USER/PERSON
(defrelation friend-of (?x ?y)))
FRIEND-OF
(assert (and (person fred) (person susi))))
((PERSON FRED) (PERSON SUSI))
(assert (friend-of fred susi))
(FRIEND-OF FRED SUSI)
(retrieve all (person ?x))
[2015-SEP-02 13:24:04.000 PL] Processing check-types agenda...
(SUSI FRED)

(retrieve all (friend-of ?x ?y))
((FRED SUSI))

-}
-------------------------------------------------------------------------=
------

module Main where
import Foreign.Ptr
import Foreign.C.String

foreign import ccall "pli_initialize"
  c_pli_initialize :: IO ()

foreign import ccall "pli_s_evaluate_to_string"
  c_pli_s_evaluate_to_string :: CString -> CString -> IO CString

pli_s_evaluate_to_string :: String -> String -> IO String
pli_s_evaluate_to_string com mod =3D=20
  withCString com $ \ ccom ->=20
    withCString mod $ \ cmod -> do
      cresult <- c_pli_s_evaluate_to_string ccom cmod
      peekCString cresult
   =20
     =20
foreign import ccall "pli_s_change_module"
  c_pli_s_change_module :: CString -> IO (Ptr ())

pli_s_change_module :: String -> IO ()
pli_s_change_module mod =3D
  withCString mod $ \ cmod -> do
    c_pli_s_change_module cmod
    return ()

foreign import ccall "pli_object_to_string"
  c_pli_object_to_string :: Ptr () -> IO CString

pli_object_to_string :: Ptr () -> IO String
pli_object_to_string p =3D do
  cs <- c_pli_object_to_string p
  peekCString cs

foreign import ccall "pli_s_evaluate"
  c_pli_s_evaluate :: CString -> CString -> IO (Ptr ())

pli_s_evaluate :: String -> String -> IO (Ptr ())
pli_s_evaluate com mod =3D
  withCString com $ \ ccom ->=20
    withCString mod $ \ cmod ->=20
      c_pli_s_evaluate ccom cmod

main =3D do
  let mod =3D "PL-USER"
 =20
  putStrLn "Initializing..."
  c_pli_initialize
  putStrLn "\n"

  let command =3D "(defconcept person)"
  putStrLn command
  pli_s_evaluate_to_string command mod >>=3D putStrLn

  -- change mod for nicer result printing:
  pli_s_change_module mod=20

  let command =3D "(defrelation friend-of (?x ?y)))"
  putStrLn command
  pli_s_evaluate_to_string command mod >>=3D putStrLn

  let command =3D "(assert (and (person fred) (person susi))))"
  putStrLn command
  pli_s_evaluate_to_string command mod >>=3D putStrLn

  let command =3D "(assert (friend-of fred susi))"
  putStrLn command
  pli_s_evaluate_to_string command mod >>=3D putStrLn

  let command =3D "(retrieve all (person ?x))"
  putStrLn command
  pli_s_evaluate_to_string command mod >>=3D putStrLn

  -- passing objects:
  let command =3D "(retrieve all (friend-of ?x ?y))"
  putStrLn command
  result <- pli_s_evaluate command mod
  pli_object_to_string result >>=3D putStrLn

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// g++ compilation:   g++ -o globals globals.cc

// Compile like this:
// setenv PL_HOME /tmp/build-kagg
// % g++ -I$PL_HOME/native/cpp -I$PL_HOME/native/cpp/stella/cpp-lib/gc/in=
clude -c pli-c-api.cc -DSTELLA_USE_GC

#include "powerloom/powerloom-system.hh"

namespace pli {
  using namespace stella;
  using namespace logic;

extern "C" void pli_initialize() {
  initialize();
}

extern "C" void* pli_s_evaluate(char* command, char* moduleName) {
  return sEvaluate(command, moduleName, NULL);
}

extern "C" char* pli_s_evaluate_to_string(char* command, char* moduleName=
) {
  Object* result;
  result =3D sEvaluate(command, moduleName, NULL);
  if (result !=3D NULL)
    return objectToString(result);
  else
    return (char*) ""; // for simplicity
}

extern "C" char* pli_object_to_string(Object* object) {
  if (object !=3D NULL)
    return objectToString(object);
  else
    return NULL;
}

extern "C" void* pli_s_change_module(char* name) {
  return sChangeModule(name, NULL);
}

}

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