Questions in the soundex algorithm

Question

I am a beginner in C ++, and I am trying to understand the Soundex algorithm that I found somewhere on the Internet. I understand most of this, but it wasn’t explained, it just fit somewhere, so there are a few lines of code that I don’t quite understand.

The Soundex algorithm implemented in the code below is as follows: http://www.blackwasp.co.uk/soundex.aspx

And here is the code:

#include <algorithm>
#include <functional>
#include <string>
#include <cctype>

using namespace std;

//----------------------------------------------------------------------------
char f_transform( char c )
  {
  string consonants[ 6 ] = { "BFPV", "CGJKQSXZ", "DT", "L", "MN", "R" };
  for (int i = 0; i < 6; i++)
    if (consonants[ i ].find( c ) != string::npos)
      return (i +1) +'0';
  return c;
  }

//----------------------------------------------------------------------------
string soundex( const string& s )
  {
  string result;

  // Validate s
  if (std::find_if(
        s.begin(),
        s.end(),
        std::not1(std::ptr_fun<int,int>(std::isalpha))
        )
      != s.end())
    return result;

  // result <-- uppercase( s )
  result.resize( s.length() );
  std::transform(
    s.begin(),
    s.end(),
    result.begin(),
    std::ptr_fun<int,int>(std::toupper)
    );

  // Convert Soundex letters to codes
  std::transform(
    result.begin() +1,
    result.end(),
    result.begin() +1,
    f_transform
    );

  // Collapse adjacent identical digits
  result.erase(
    std::unique(
      result.begin() +1,
      result.end()
      ),
    result.end()
    );

  // Remove all non-digits following the first letter
  result.erase(
    std::remove_if(
      result.begin() +1,
      result.end(),
      std::not1(std::ptr_fun<int,int>(std::isdigit))
      ),
      result.end()
    );

  result += "000";
  result.resize( 4 );

  return result;
  }

// end soundex.cpp 

I get most of this, except for two things: 1. where the "string s check" is done:

if (std::find_if(
        s.begin(),
        s.end(),
        std::not1(std::ptr_fun<int,int>(std::isalpha))
        )
      != s.end())
    return result;

"ptr_fun". google, . , , "s.begin()" - , , . , isalpha, - . , , , , " " , :).

2. , , - :

   // result.erase(   :: (     result.begin() +1,     result.end()     ),   result.end()   );

   // , result.erase(   :: remove_if (     result.begin() +1,     result.end(),     :: not1 (:: ptr_fun (:: isdigit))     ),     result.end()   );

, , , . , "" " , ". "erase" [first, last], , . , , - :

std::unique(result.begin() + 1, result.end() ); ??

""? :

• "abaace" , "" "abace", ( "abace", "e" ), , . , , . , .