RubyからHaslekkで記述した関数を呼び出すサンプルの説明です。

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9. foreign import ccall ”math.h sin”
sin :: CDouble -> CDouble
foreign export ccall ”fact”
fact :: CInt -> CInt

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11. == factorial.hs ==
Module Factorial where
import Foreign.C.Types
foreign export ccall ”factorial”
factorial :: CInt -> Cint
factorial 0 = 1
factorial x = x * factorial(x-1)

13. == main.c ==
#include <stdio.h>
#include “factorial_stub.h”
int main(int argc, char* argv[])
{
hs_init(&argc, &argv);
printf(“%dn”, fact(5));
hs_exit();
return 0;
}

14. $ ghc -shared -dynamic
... ( )

15. #include <ruby.h>
#include "factorial_stub.h"
static VALUE rb_factorial(VALUE self, VALUE val)
{
return UINT2NUM(factorial(NUM2UINT(val)));
}
void Init_factorial(void)
{
hs_init(NULL, NULL);// Haskell ..
rb_define_module_function(rb_mMath, "factorial",
RUBY_METHOD_FUNC(rb_factorial), 1);
}

16. (gem install )
$ irb -r factorial/factorial
irb(main):001:0> Math.factorial 4
=> 24

17. foreign export ccall ”factorial”
factorial :: CInt -> CInt
CInt -229 +229-1
9 362,880
10 3,628,800
15 1.30767E+12

21. $ cd `ghc --print-libdir`
�

24. require 'rbconfig'
TARGET = 'factorial'
C_SRC = %w{ main.c }
HS_SRC = %w{ factorial.hs }
HS_LIBS = %w{ base integer-gmp ghc-prim }
CONF = RbConfig::MAKEFILE_CONFIG
VALS = %w{prefix includedir RUBY_BASE_NAME ruby_version
rubyhdrdir arch MKDIR_P INSTALL INSTALL_PROGRAM}.map{|k|
"#{k}=#{CONF[k]}"
}.join("n")
GHC_LIBDIR=`ghc --print-libdir`.strip
FLAGS = "FLAGS=-I$(rubyhdrdir) -I$(rubyhdrdir)/$(arch) -
shared -dynamic -no-hs-main -lHSrts -lffin"
+ "FLAGS+=-no-auto-link-packages -I#{GHC_LIBDIR}/
include -L#{GHC_LIBDIR}n"
+ HS_LIBS.map{|l|
'FLAGS+=' + `ghc-pkg describe #{l}|sed -ne 's/
library-dirs: /-L/p;s/hs-libraries: /-l/p;'`.gsub(/n/, ' ')
}.join("n")
+ "nFLAGS+=-lgmpn"

25. File.open("Makefile", "w") {|f|
f.puts <<__MAKEFILE__
TARGET=#{TARGET}.#{CONF['DLEXT']}
HS_SRC=#{HS_SRC.join(' ')}
C_SRC=#{C_SRC.join(' ')}
#{VALS}
#{FLAGS}
STUB=$(HS_SRC:.hs=_stub.o)
all : $(TARGET)
$(STUB) : $(HS_SRC)
ghc $<
$(TARGET) : $(C_SRC) $(STUB) $(HS_SRC:.hs=.o)
ghc -o $@ $^ $(FLAGS)
install:
$(MKDIR_P) ../lib/#{TARGET}/
$(INSTALL_PROGRAM) $(TARGET) ../lib/#{TARGET}/
clean:
rm -f $(TARGET) $(C_SRC:.c=.o) $(HS_SRC:.hs=.hi) $
(HS_SRC:.hs=.o) $(HS_SRC:.hs=_stub.)*
__MAKEFILE__
}

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