// istring2.cpp
#include "istring2.h"

int numeric( const string &s ) {
  size_t n = s.find_first_not_of("0123456789");
  if ( n == NPOS ) return 1;
  if ( n != 0 )    return 0;
  if ( s.is_null() ) return 0;
  if ( s.find_first_of("+-") != 0 ) return 0;
  n = s.find_first_not_of("0123456789",1);  // Pal 2. jos "-4" ???
  return ( n >= s.length() );
}

string add(const string &s1,const string &s2) {
  if ( numeric(s1) && numeric(s2) ) return itostr(int_val(s1) + int_val(s2));
  return string(s1).append(s2);
}

string operator+(char c, const Istring &s)          { return add(string(c),s);  }
string operator+(const Istring &s, char c)          { return add(s,string(c));  }
string operator+(int i, const Istring &s)           { return add(itostr(i),s);  }
string operator+(const Istring &s, int i)           { return add(s,itostr(i));  }
string operator+(const Istring &s1, const char *s2) { return add(s1,string(s2));}
string operator+(const Istring &s1, const Istring &s2) { return add(s1,s2);     }
string operator+(const char *s1, const Istring &s2) { return add(string(s1),s2);}