Implement initial wrapper

Author: certik

src/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(SRC
-	basic.f90
+    wrapper.c
+    basic.f90
     )
 
 include_directories(BEFORE ${python_wrapper_BINARY_DIR}/symengine/lib)

src/wrapper.c

@@ -0,0 +1,19 @@
+#include <symengine/cwrapper.h>
+
+void f(int i)
+{
+    char *s;
+    basic x, y, e, n;
+    basic_new_stack(x);
+    basic_new_stack(y);
+    basic_new_stack(e);
+    basic_new_stack(n);
+    symbol_set(x, "x");
+    symbol_set(y, "y");
+    integer_set_si(n, i);
+    basic_mul(e, n, x);
+    basic_add(e, e, y);
+    s = basic_str(e);
+    printf("Result: %s", s);
+    basic_str_free(s);
+}