fix Fp on neg input

WeiqiNs · Oct 31, 2024 · 23f9f0b · 23f9f0b
1 parent 85324ea
commit 23f9f0b
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Showing 2 changed files with 26 additions and 2 deletions.
diff --git a/src/field.cpp b/src/field.cpp
@@ -34,8 +34,17 @@ void Field::mod(Fp& x) const{
 
 Fp Field::from_int(const int& x) const{
     Fp r;
-    bn_set_dig(r.value, x);
-    mod(r);
+
+    // Check if the input integer is negative.
+    if (x >= 0){
+        bn_set_dig(r.value, x);
+        mod(r);
+    } else{
+        bn_set_dig(r.value, -x);
+        mod(r);
+        r = neg(r);
+    }
+
     return r;
 }
 

diff --git a/tests/test_field.cpp b/tests/test_field.cpp
@@ -1,6 +1,21 @@
 #include <gtest/gtest.h>
 #include "bp.hpp"
 
+TEST(FieldElementTests, FromInt){
+    // Initialize the scheme.
+    BP::init();
+
+    // Create a field.
+    const Field Zp(11);
+
+    // Perform testing.
+    const Fp x = Zp.from_int(-17);
+
+    // Test and then clear the core.
+    EXPECT_TRUE(Field::cmp(x, 5));
+    BP::close();
+}
+
 TEST(FieldElementTests, Add){
     // Initialize the scheme.
     BP::init();