Fixed incompatibility of mod operation

Author: rajithv

ext/symengine/ruby_ntheory.c

@@ -13,7 +13,9 @@ VALUE cntheory_lcm(VALUE self, VALUE operand1, VALUE operand2) {
 }
 
 VALUE cntheory_mod(VALUE self, VALUE operand1, VALUE operand2) {
-    return function_twoarg(ntheory_mod, operand1, operand2);
+    VALUE ans = function_twoarg(ntheory_mod, operand1, operand2);
+    VALUE ans1 = cbasic_add(ans, operand2);
+    return function_twoarg(ntheory_mod, ans1, operand2);
 }
 
 VALUE cntheory_quotient(VALUE self, VALUE operand1, VALUE operand2) {

ext/symengine/ruby_ntheory.h

@@ -5,6 +5,7 @@
 #include <symengine/cwrapper.h>
 
 #include "symengine.h"
+#include "ruby_basic.h"
 #include "symengine_utils.h"
 
 VALUE cntheory_onearg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*), VALUE operand1);

ext/symengine/symengine_utils.c

@@ -128,7 +128,8 @@ VALUE function_onearg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*), VA
     return result;
 }
 
-VALUE function_twoarg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*, const basic_struct*), VALUE operand1, VALUE operand2) {
+VALUE function_twoarg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*, const basic_struct*),
+                      VALUE operand1, VALUE operand2) {
     basic_struct *cresult;
     VALUE result;
 

ext/symengine/symengine_utils.h

@@ -12,7 +12,8 @@ VALUE Klass_of_Basic(const basic_struct *basic_ptr);
 //Returns the result from the function pointed by cwfunc_ptr: for one argument functions
 VALUE function_onearg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*), VALUE operand1);
 //Returns the result from the function pointed by cwfunc_ptr: for two argument functions
-VALUE function_twoarg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*, const basic_struct*), VALUE operand1, VALUE operand2);
+VALUE function_twoarg(void (*cwfunc_ptr)(basic_struct*, const basic_struct*, const basic_struct*),
+                      VALUE operand1, VALUE operand2);
 
 //Obtains the value from Ruby Fixnum or Bignum to an already allocated basic_struct
 #define GET_SYMINTFROMVAL(num_value, this) { \

spec/ntheory_spec.rb

@@ -40,6 +40,24 @@
           expect(f).to eql(1)
         end
       end
+      context '-5 mod -4' do
+        it 'returns -1' do
+          f = SymEngine::mod(-5, -4)
+          expect(f).to eql(-1)
+        end
+      end
+      context '5 mod -4' do
+        it 'returns -3' do
+          f = SymEngine::mod(5, -4)
+          expect(f).to eql(-3)
+        end
+      end
+      context '-5 mod 4' do
+        it 'returns 3' do
+          f = SymEngine::mod(-5, 4)
+          expect(f).to eql(3)
+        end
+      end
     end
 
     describe '#quotient' do