add utils::logical() function to complement the *numeric() functions

src/utils.h

@@ -160,6 +160,19 @@ namespace utils {
   std::string check_packages_for_style(const std::string &style, const std::string &name,
                                        LAMMPS *lmp);
 
+  /*! Convert a string to a boolean while checking whether it is a valid boolean term.
+   *  Valid terms are 'yes', 'no', 'true', 'false', 'on', 'off', '1', '0'. Capilatization
+   *  will be ignored (thus 'yEs' or 'nO' are valid, 'yay' or 'nay' are not).
+   *
+   *  \param file     name of source file for error message
+   *  \param line     line number in source file for error message
+   *  \param str      string to be converted to logical
+   *  \param do_abort determines whether to call Error::one() or Error::all()
+   *  \param lmp      pointer to top-level LAMMPS class instance
+   *  \return         boolean */
+
+  bool logical(const char *file, int line, const char *str, bool do_abort, LAMMPS *lmp);
+
   /*! Convert a string to a floating point number while checking
    *  if it is a valid floating point or integer number
    *