Fix two's complement abs

DanielKrawisz · Dec 29, 2023 · 6b90fd0 · 6b90fd0
1 parent ad222e5
commit 6b90fd0
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Showing 4 changed files with 12 additions and 13 deletions.
diff --git a/include/data/encoding/integer.hpp b/include/data/encoding/integer.hpp
@@ -631,6 +631,7 @@ namespace data::encoding::signed_decimal {
 
     template <endian::order r>
     std::ostream &write (std::ostream &w, const math::number::Z_bytes<r, complement::twos> &z) {
+        if (math::is_zero (z)) return w << "0";
         if (math::is_negative (z)) w << "-";
         return decimal::write (w, math::number::N_bytes<r>::read (data::abs (z)));
     }
@@ -1370,7 +1371,7 @@ namespace data::math {
     template <hex_case zz>
     hex::int2<zz> inline abs<hex::int2<zz>>::operator () (const hex::int2<zz> &x) {
         if (!x.valid ()) throw exception {} << "invalid hexidecimal string: " << x;
-        return math::number::sign_bit_set (x) ? -x : math::number::trim (x);
+        return math::is_negative (x) ? -x : x;
     }
 
 }

diff --git a/include/data/math/number/bytes/Z.hpp b/include/data/math/number/bytes/Z.hpp
@@ -422,7 +422,7 @@ namespace data::math {
     abs<number::Z_bytes<r, number::complement::twos>>::operator ()
     (const number::Z_bytes<r, number::complement::twos> &x)
     {
-        return number::arithmetic::trim<r, number::complement::twos, byte> (number::arithmetic::twos::abs<r, byte> (x));
+        return is_negative (x) ? -x : x;
     }
 
     template <endian::order r>

diff --git a/test/testTwosComplement.cpp b/test/testTwosComplement.cpp
@@ -82,18 +82,16 @@ namespace data::math::number {
     } struct test_abs : virtual test_zero<Z> {
         test_abs () {
 
-            // abs always converts to the minimal representation.
+            // abs will not change the number if it is not negative.
+            // otherwise, it will return the minimal representation.
 
-            auto zero0 = Z::zero (0, false);
-            auto abs_zero1neg = data::abs (Z::zero (1, true));
-
-            EXPECT_TRUE (identical (abs_zero1neg, zero0)) << "expected " << abs_zero1neg << " === " << zero0;
-            EXPECT_TRUE (identical (data::abs (Z::zero (2, true)), zero0));
-            EXPECT_TRUE (identical (data::abs (Z::zero (3, true)), zero0));
+            EXPECT_TRUE (identical (data::abs (Z::zero (1, true)), Z::zero (1, true)));
+            EXPECT_TRUE (identical (data::abs (Z::zero (2, true)), Z::zero (2, true)));
+            EXPECT_TRUE (identical (data::abs (Z::zero (3, true)), Z::zero (3, true)));
 
             EXPECT_TRUE (identical (data::abs (Z::read ("0x01")), Z::read ("0x01")));
-            EXPECT_TRUE (identical (data::abs (Z::read ("0x0001")), Z::read ("0x01")));
-            EXPECT_TRUE (identical (data::abs (Z::read ("0x000001")), Z::read ("0x01")));
+            EXPECT_TRUE (identical (data::abs (Z::read ("0x0001")), Z::read ("0x0001")));
+            EXPECT_TRUE (identical (data::abs (Z::read ("0x000001")), Z::read ("0x000001")));
 
             EXPECT_TRUE (data::identical (data::abs (Z::read ("0x81")), -Z::read ("0x81")));
             EXPECT_TRUE (data::identical (data::abs (Z::read ("0x8001")), -Z::read ("0x81")));

diff --git a/test/testZBytes.cpp b/test/testZBytes.cpp
@@ -275,8 +275,8 @@ namespace data {
 
             auto write_zb = encoding::signed_decimal::write (zb);
             auto write_zl = encoding::signed_decimal::write (zl);
-            EXPECT_EQ (write_zb, "0") << "expected " << std::hex << zb << " to write as " << write_zb;
-            EXPECT_EQ (write_zl, "0") << "expected " << std::hex << zl << " to write as " << write_zl;
+            EXPECT_EQ (write_zb, "0") << "expected " << std::hex << zb << " to write as 0 but got " << write_zb;
+            EXPECT_EQ (write_zl, "0") << "expected " << std::hex << zl << " to write as 0 but got " << write_zl;
         }
     }