Treat "-0" as "0"

"0" and "-0" are mathematically identical so it should they should
treated as the same value.

Zero is considered neither positive nor negative, so `isPositive()` and
`isNegative()` both return `false`. This is consistent with `signum()`.

Author: julienfalque

php_decimal.c

@@ -592,6 +592,17 @@ static void php_decimal_set_nan(php_decimal_t *obj)
     php_decimal_mpd_set_nan(PHP_DECIMAL_MPD(obj));
 }
 
+/**
+ * Sets the value to "0" in case it is "-0"
+ */
+static void php_decimal_prevent_negative_zero(mpd_t *mpd)
+{
+    if (mpd_iszero(mpd) && mpd_isnegative(mpd)) {
+        uint32_t status = 0;
+        mpd_qcopy_negate(mpd, mpd, &status);
+    }
+}
+
 /**
  * Parses a string to a given precision. Trailing zeroes are not preserved.
  */
@@ -617,6 +628,8 @@ static php_success_t php_decimal_mpd_set_string(mpd_t *mpd, zend_string *str, ze
         php_decimal_loss_of_data_on_string_conversion();
     }
 
+    php_decimal_prevent_negative_zero(mpd);
+
     return SUCCESS;
 }
 
@@ -1157,12 +1170,16 @@ static void php_decimal_ceil(php_decimal_t *res, mpd_t *op1)
  */
 static void php_decimal_truncate(php_decimal_t *res, mpd_t *op1)
 {
+    mpd_t *mpd = PHP_DECIMAL_MPD(res);
     uint32_t status = 0;
+
     if (mpd_isspecial(op1)) {
-        mpd_qcopy(PHP_DECIMAL_MPD(res), op1, &status);
+        mpd_qcopy(mpd, op1, &status);
         return;
     }
-    mpd_qtrunc(PHP_DECIMAL_MPD(res), op1, php_decimal_context(), &status);
+
+    mpd_qtrunc(mpd, op1, php_decimal_context(), &status);
+    php_decimal_prevent_negative_zero(mpd);
 }
 
 /**
@@ -1197,6 +1214,12 @@ static void php_decimal_abs(php_decimal_t *res, mpd_t *op1)
 static void php_decimal_negate(php_decimal_t *res, mpd_t *op1)
 {
     uint32_t status = 0;
+
+    if (mpd_iszero(op1)) {
+        mpd_qcopy(PHP_DECIMAL_MPD(res), op1, &status);
+        return;
+    }
+
     mpd_qcopy_negate(PHP_DECIMAL_MPD(res), op1, &status);
 }
 
@@ -1433,6 +1456,8 @@ static void php_decimal_do_binary_op(php_decimal_binary_op_t op, php_decimal_t *
     php_decimal_set_precision(res, prec);
     op(res, mpd1, mpd2);
     mpd_del(&tmp);
+
+    php_decimal_prevent_negative_zero(PHP_DECIMAL_MPD(res));
 }
 
 
@@ -2201,7 +2226,10 @@ PHP_DECIMAL_METHOD(round)
         #endif
     ZEND_PARSE_PARAMETERS_END();
 
-    php_decimal_round_mpd(PHP_DECIMAL_MPD(res), PHP_DECIMAL_MPD(obj), places, rounding);
+    mpd_t *mpd = PHP_DECIMAL_MPD(res);
+    php_decimal_round_mpd(mpd, PHP_DECIMAL_MPD(obj), places, rounding);
+    php_decimal_prevent_negative_zero(mpd);
+
     RETURN_DECIMAL(res);
 }
 
@@ -2373,7 +2401,10 @@ PHP_DECIMAL_ARGINFO_END()
 PHP_DECIMAL_METHOD(isPositive)
 {
     PHP_DECIMAL_PARAMS_PARSE_NONE();
-    RETURN_BOOL(mpd_ispositive(THIS_MPD()));
+
+    mpd_t *mpd = THIS_MPD();
+
+    RETURN_BOOL(!mpd_iszero(mpd) && mpd_ispositive(mpd));
 }
 
 /**
@@ -2384,7 +2415,10 @@ PHP_DECIMAL_ARGINFO_END()
 PHP_DECIMAL_METHOD(isNegative)
 {
     PHP_DECIMAL_PARAMS_PARSE_NONE();
-    RETURN_BOOL(mpd_isnegative(THIS_MPD()));
+
+    mpd_t *mpd = THIS_MPD();
+
+    RETURN_BOOL(!mpd_iszero(mpd) && mpd_isnegative(mpd));
 }
 
 /**

tests/php7/cast.phpt

@@ -19,7 +19,7 @@ $tests = [
      * STRING
      */
     [(string) decimal(),                "0"],
-    [(string) decimal("-0"),           "-0"],
+    [(string) decimal("-0"),            "0"],
     [(string) decimal("5.2"),           "5.2"],
 
     [(string) decimal( "NAN"),          "NAN"],

tests/php7/clone.phpt

@@ -11,6 +11,12 @@ use Decimal\Decimal;
 $a = new Decimal("1.234", 16);
 $b = clone $a;
 
+var_dump($a);
+var_dump($b);
+
+$a = new Decimal("-0");
+$b = clone $a;
+
 var_dump($a);
 var_dump($b);
 ?>
@@ -27,3 +33,15 @@ object(Decimal\Decimal)#2 (2) {
   ["precision"]=>
   int(16)
 }
+object(Decimal\Decimal)#3 (2) {
+  ["value"]=>
+  string(1) "0"
+  ["precision"]=>
+  int(28)
+}
+object(Decimal\Decimal)#1 (2) {
+  ["value"]=>
+  string(1) "0"
+  ["precision"]=>
+  int(28)
+}

tests/php7/empty.phpt

@@ -10,6 +10,7 @@ use Decimal\Decimal;
 
 var_dump(empty(new Decimal()));
 var_dump(empty(new Decimal(0)));
+var_dump(empty(new Decimal('-0')));
 var_dump(empty(new Decimal(1)));
 
 var_dump(empty(new Decimal( "1E-1000")));
@@ -28,3 +29,4 @@ bool(false)
 bool(false)
 bool(false)
 bool(false)
+bool(false)

tests/php7/json.phpt

@@ -9,9 +9,11 @@ if (!extension_loaded("json"))    echo 'skip';
 <?php
 use Decimal\Decimal;
 
+var_dump(json_encode(new Decimal("-0", 20)));
 var_dump(json_encode(new Decimal("1.2345", 20)));
 var_dump(json_encode(new Decimal("5.0000", 20)));
 ?>
 --EXPECT--
+string(3) ""0""
 string(8) ""1.2345""
 string(8) ""5.0000""

tests/php7/methods/abs.phpt

@@ -14,6 +14,9 @@ use Decimal\Decimal;
 function decimal(...$args) { return new Decimal(...$args); }
 
 $tests = [
+    ["0", "0"],
+    ["-0", "0"],
+
     ["-0.1", "0.1"],
     ["+0.1", "0.1"],
     [ "0.1", "0.1"],

tests/php7/methods/avg.phpt

@@ -39,6 +39,9 @@ $tests = [
     [[array('-2.3', '4.1', 5),   ], "2.266666666666666666666666667",   28],
     [[array('-2.3', '4.1', 5), 10], "2.266666667",                     10],
     [[array('-2.3', '4.1', 5), 30], "2.26666666666666666666666666667", 30],
+
+    [[[decimal("0.1"), decimal("-0.1")]], "0.0", 28],
+    [[[decimal("-0.1"), decimal("0.1")]], "0.0", 28],
 ];
 
 foreach ($tests as $index => $test) {

tests/php7/methods/ceil.phpt

@@ -14,6 +14,9 @@ use Decimal\Decimal;
 function decimal(...$args) { return new Decimal(...$args); }
 
 $tests = [
+    ["0",          "0"],
+    ["-0",         "0"],
+
     ["-0.1",       "-0"],
     [ "0.1",        "1"],
 

tests/php7/methods/compareTo.phpt

@@ -29,6 +29,11 @@ $tests = [
     [decimal(),     false,  1],
     [decimal(),     0.0,    0],
 
+    [decimal("-0"), 0,      0],
+    [decimal("-0"), null,   1],
+    [decimal("-0"), false,  1],
+    [decimal("-0"), 0.0,    0],
+
     [decimal(1),    0,      1],
     [decimal(1),    null,   1],
     [decimal(1),    false,  1],

tests/php7/methods/copy.phpt

@@ -11,6 +11,11 @@ $dst = $src->copy();
 
 var_dump($src, $dst);
 
+$src = new Decimal\Decimal("-0", 32);
+$dst = $src->copy();
+
+var_dump($src, $dst);
+
 ?>
 --EXPECT--
 object(Decimal\Decimal)#1 (2) {
@@ -25,3 +30,15 @@ object(Decimal\Decimal)#2 (2) {
   ["precision"]=>
   int(32)
 }
+object(Decimal\Decimal)#3 (2) {
+  ["value"]=>
+  string(1) "0"
+  ["precision"]=>
+  int(32)
+}
+object(Decimal\Decimal)#1 (2) {
+  ["value"]=>
+  string(1) "0"
+  ["precision"]=>
+  int(32)
+}