Определить, к какому элементу массива принадлежит считываемый символ

const int M=8;
char* const alphabet[M] = {"\t\r\n ", "a-z", "A-Z", "0-9", ".", ",", ":", ";"};
 
char Ch;    
ifstream fin("input.txt");
fin.get(Ch);

// Copyright (C) 2007-2014 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file bits/c++0x_warning.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{iosfwd}
 */
 
#ifndef _CXX0X_WARNING_H
#define _CXX0X_WARNING_H 1
 
#if __cplusplus < 201103L
#error This file requires compiler and library support for the \
ISO C++ 2011 standard. This support is currently experimental, and must be \
enabled with the -std=c++11 or -std=gnu++11 compiler options.
#endif
 
#endif