[libcxx][NFC] tidy up money_get::__do_get's sign parsing

[DanielMcIntosh-IBM]

Summary

Same logic, but much easier to read this way

[Mordante]

Thanks, this indeed looks better readable!
LGTM, but I prefer to remove the unneeded assignment.

libcxx/include/locale

2969

The original algorithm never sets __neg to false. Looking at the code it seems the call-site always sets this value to false.

[DanielMcIntosh-IBM]

libcxx/include/locale

2969

True, however, as you mentioned, the call-site always sets the value to false, so this isn't actually a functional change.

I'm open to other ideas, but explicitly setting __neg to false when we detect a positive seems more illustrative to me, and generally safer.

Additionally, explicitly setting it to false here means that the only case where we _don't_ set __neg is when __psn.size() == 0 && __nsn.size() == 0 - i.e. when the locale has no means of specifying a positive or negative value. This lets us use the initial value of __neg as a default value for that case.

[DanielMcIntosh-IBM]

Add comment further explaining the behaviour of __neg

[Mordante]

LGTM!

libcxx/include/locale

2969

Fair points.

libcxx/include/locale

for (unsigned __p = 0; __p < 4 && __b != __e; ++__p)
         case money_base::none:
             if (__p != 3)
             {
                 while (__b != __e && __ct.is(ctype_base::space, *__b))
                     __spaces.push_back(*__b++);
             }
             break;
         case money_base::sign:
-            if (__psn.size() + __nsn.size() > 0)
-            {
-                if (__psn.size() == 0 || __nsn.size() == 0)
-                {   // sign is optional
-                    if (__psn.size() > 0)
-                    {   // __nsn.size() == 0
-                        if (*__b == __psn[0])
-                        {
-                            ++__b;
-                            if (__psn.size() > 1)
-                                __trailing_sign = &__psn;
-                        }
-                        else
-                            __neg = true;
-                    }
-                    else if (*__b == __nsn[0])  // __nsn.size() > 0 &&  __psn.size() == 0
-                    {
-                        ++__b;
-                        __neg = true;
-                        if (__nsn.size() > 1)
-                            __trailing_sign = &__nsn;
-                    }
-                }
-                else  // sign is required
-                {
-                    if (*__b == __psn[0])
-                    {
-                        ++__b;
-                        if (__psn.size() > 1)
-                            __trailing_sign = &__psn;
-                    }
-                    else if (*__b == __nsn[0])
-                    {
-                        ++__b;
-                        __neg = true;
-                        if (__nsn.size() > 1)
-                            __trailing_sign = &__nsn;
-                    }
-                    else
-                    {
-                        __err |= ios_base::failbit;
-                        return false;
-                    }
-                }
-            }
+            if (__psn.size() > 0 && *__b == __psn[0])
+                __neg = false;
+                break;
+            if (__nsn.size() > 0 && *__b == __nsn[0])
+                break;
+            if (__psn.size() > 0 && __nsn.size() > 0)
+            {   // sign is required
+            if (__psn.size() == 0 && __nsn.size() == 0)
+                // locale has no way of specifying a sign. Use the initial value of __neg as a default
+                break;
+            __neg = (__nsn.size() == 0);
             break;
         case money_base::symbol:
             {
             bool __more_needed = __trailing_sign ||
                                  (__p < 2)       ||
                                  (__p == 2 && __pat.field[3] != static_cast<char>(money_base::none));
             bool __sb = (__flags & ios_base::showbase) != 0;
             if (__sb || __more_needed)