+ /**
+ * Is this a known char from some language?
+ * If \p preamble is empty and code point \p c is known to belong
+ * to a supported script, true is returned and \p preamble is set
+ * to the corresponding entry in the unicodesymbols file.
+ * If \p preamble is not empty, a check is made whether code point
+ * \p c is a known character matching the preamble entry.
+ */
+ static bool isKnownScriptChar(char_type const c, std::string & preamble);