+/* Test whether string[start_index..end_index-1] is a valid textual
+ representation of NaN. */
+static int
+strisnan (const char *string, size_t start_index, size_t end_index, int uppercase)
+{
+ if (start_index < end_index)
+ {
+ if (string[start_index] == '-')
+ start_index++;
+ if (start_index + 3 <= end_index
+ && memcmp (string + start_index, uppercase ? "NAN" : "nan", 3) == 0)
+ {
+ start_index += 3;
+ if (start_index == end_index
+ || (string[start_index] == '(' && string[end_index - 1] == ')'))
+ return 1;
+ }
+ }
+ return 0;
+}
+