[YAML] Fix glitch in formatDouble serialization

Previous implementation assumed number format with four letter exponent
blocks; this fix ensures that formatting is correct for very small/large
numbers that use five letter exponent blocks (e.g. 'e+100')

src/base/AnyMap.cpp

@@ -171,7 +171,15 @@ string formatDouble(double x, long int precision)
     string s0;
     if (useExp) {
         s0 = fmt::format(fmt::format("{:.{}e}", x, precision));
-        last = s0.size() - 5; // last digit of significand
+        // last digit of significand
+        last = s0.size() - 5;
+        if (s0[last + 1] == 'e') {
+            // pass - most values use four letter exponent (examples: e+05, e-03)
+        } else if (s0[last + 2] == 'e') {
+            last++; // exponents larger than e+99 or smaller than e-99
+        } else {
+            last = s0.find('e') - 1; // backstop; slower, but will always work
+        }
     } else {
         log10x = static_cast<int>(std::floor(std::log10(std::abs(x))));
         s0 = fmt::format("{:.{}f}", x, precision - log10x);

test/general/test_serialization.cpp

@@ -38,6 +38,9 @@ TEST(YamlWriter, formatDouble)
     // check edge cases
     m["a"] = -1061.793215682400;
     EXPECT_EQ(m.toYamlString(), "a: -1061.7932156824\n");
+
+    m["a"] = 7.820059054328200e-111;
+    EXPECT_EQ(m.toYamlString(), "a: 7.8200590543282e-111\n");
 }
 
 TEST(YamlWriter, formatDoubleExp)