Add helper function

From cppcheck#4701
Co-authored-by: gerboengels [email protected]

simplecpp.h

@@ -120,7 +120,7 @@ namespace simplecpp {
             name = (std::isalpha(static_cast<unsigned char>(string[0])) || string[0] == '_' || string[0] == '$')
                    && (std::memchr(string.c_str(), '\'', string.size()) == nullptr);
             comment = string.size() > 1U && string[0] == '/' && (string[1] == '/' || string[1] == '*');
-            number = std::isdigit(static_cast<unsigned char>(string[0])) || (string.size() > 1U && (string[0] == '-' || string[0] == '+') && std::isdigit(static_cast<unsigned char>(string[1])));
+            number = isNumberLike(string);
             op = (string.size() == 1U && !name && !comment && !number) ? string[0] : '\0';
         }
 
@@ -135,6 +135,10 @@ namespace simplecpp {
         bool isOneOf(const char ops[]) const;
         bool startsWithOneOf(const char c[]) const;
         bool endsWithOneOf(const char c[]) const;
+        static bool SIMPLECPP_LIB isNumberLike(const std::string& str) {
+            return std::isdigit(static_cast<unsigned char>(str[0])) ||
+                   (str.size() > 1U && (str[0] == '-' || str[0] == '+') && std::isdigit(static_cast<unsigned char>(str[1])));
+        }
 
         TokenString macro;
         char op;