Add ability to assign ruby complex types to GSL::Matrix::Complex (#38)

* * Added a case for `T_COMPLEX` in rb_gsl_complex_new(1..2) and rb_gsl_obj_to_gsl_complex(1)
* Currently the ops on `::Complex` number is handled via rb_funcall(2..)

* Added a test for creating `GSL::Complex` by passing `Complex ` type to `GSL::Complex#alloc`

* There is an added cost due to the call to rb_funcall(2..) being used since the @real, @image ivars appear to be unset, in addition to this, struct RComplex is not publicly exposed and to use TypedData_Get_Struct(3) this struct would need to be replicated along with all its dependants.

* Fixed a typo that led to failing tests

ext/gsl_native/complex.c

@@ -41,6 +41,11 @@ gsl_complex rb_gsl_obj_to_gsl_complex(VALUE obj, gsl_complex *z)
     if (!NIL_P(vre)) GSL_SET_REAL(z, NUM2DBL(vre));
     if (!NIL_P(vim)) GSL_SET_IMAG(z, NUM2DBL(vim));
     break;
+  case T_COMPLEX:
+    vre = rb_funcall(obj, rb_intern("real"), 0);
+    vim = rb_funcall(obj, rb_intern("imag"), 0);
+    *z = gsl_complex_rect(NUM2DBL(vre), NUM2DBL(vim));
+    break;
   case T_FLOAT:
   case T_FIXNUM:
   case T_BIGNUM:
@@ -63,14 +68,19 @@ gsl_complex rb_gsl_obj_to_gsl_complex(VALUE obj, gsl_complex *z)
 static VALUE rb_gsl_complex_new(int argc, VALUE *argv, VALUE klass)
 {
   gsl_complex *c = NULL;
-  VALUE obj;
+  VALUE obj, vre, vim;
   obj = Data_Make_Struct(klass, gsl_complex, 0, free, c);
   switch (argc) {
   case 1:
     switch (TYPE(argv[0])) {
     case T_ARRAY:
       *c = ary2complex(argv[0]);
       break;
+    case T_COMPLEX:
+      vre = rb_funcall(argv[0], rb_intern("real"), 0);
+      vim = rb_funcall(argv[0], rb_intern("imag"), 0);
+      *c = gsl_complex_rect(NUM2DBL(vre), NUM2DBL(vim));
+      break;
     case T_FLOAT:
     case T_FIXNUM:
     case T_BIGNUM:

test/gsl/complex_test.rb

@@ -16,5 +16,16 @@ def test_complex
         'gsl_complex_polar imag part at (r=%g,t=%g)' % [r, t]
     }
   end
-
+
+  # Test if it is possible to create a GSL::Complex from ::Complex
+  def test_rb_complex_creation
+    rb_comp = Complex(rand, rand)
+
+    z = GSL::Complex.alloc(rb_comp)
+
+    assert_rel z.real, rb_comp.real, GSL::DBL_EPSILON,
+      "gsl_complex real part.  Re(#{rb_comp}) = #{z.real}"
+    assert_rel z.imag, rb_comp.imag, GSL::DBL_EPSILON,
+      "gsl_complex imag part.  Im(#{rb_comp}) = #{z.imag}"
+  end
 end