title: error: invalid in-class initialization of static data member of non-integral type 'const char[]'
body: <p>I'm getting tons of errors on my private class members. Please help me work through them. </p>
  
  <p>error: a brace-enclosed initializer is not allowed here before '{' token</p>
  
  <p>error: invalid in-class initialization of static data member of non-integral type 'const char []'</p>
  
  <p>error: 'LETTERS_ARR' has not been declared</p>
  
  <p>error: 'LETTERS_ARR' has not been declared</p>
  
  <p>error: expected ',' or '...' before '+' token</p>
  
  <p>error: ISO C++ forbids initialization of member 'SNTNC_SMLRTY_THRSHLD_DEFAULT'</p>
  
  <p>error: making 'SNTNC_SMLRTY_THRSHLD_DEFAULT' static**</p>
  
  <pre><code>private:
      std::vector&lt;std::string&gt; files_vec; 
      std::vector&lt;std::string&gt; get_file_sntncs(std::fstream&amp;);
      std::vector&lt;std::string&gt; get_sntnc_wrds(const std::string&amp;);
      double sntnc_smlrty_qtnt(std::vector&lt;std::string&gt;, std::vector&lt;std::string&gt;);
      static const char LETTERS_ARR[] = {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'."};
      static const std::set&lt;char&gt; LETTERS_SET(LETTERS_ARR, LETTERS_ARR + sizeof(LETTERS_ARR)/sizeof(char));
      double sntnc_smlrty_thrshld; 
      static const double SNTNC_SMLRTY_THRSHLD_DEFAULT = 0.5; 
  </code></pre>