with sql_exceptions;

package body sql_enumeration_pkg is
   
   null_value_error : exception renames sql_exceptions. null_value_error;
   
   function null_sql_enumeration return sql_enumeration is
      
      null_holder : sql_enumeration;
    
   begin 
      return null_holder;
   end;
   
   
   function without_null 
      (value :  sql_enumeration) 
      return sql_enumeration_not_null 
   is
   begin 
      if value. is_null then
         raise null_value_error;
      else
         return value. value;
      end if;
   end without_null;
   
   
   function with_null 
      (value : sql_enumeration_not_null) 
      return sql_enumeration 
   is
   begin 
      return (is_null => false, value => value);
   end;
   
   
   procedure assign 
      (left : in out sql_enumeration; 
       right : in sql_enumeration) 
   is
   begin 
      left := right;
   end assign;
   
   
   function equals (left, right : sql_enumeration) return boolean_with_unknown 
   is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value = right. value then
         return true;
      else
         return false;
      end if;
   end equals;
   
   
   function not_equals (left, right : sql_enumeration) return boolean_with_unknown 
   is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value /= right. value then
         return true;
      else
         return false;
      end if;
   end not_equals;
   
   
   function "<" (left, right : sql_enumeration) return boolean_with_unknown is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value < right. value then
         return true;
      else
         return false;
      end if;
   end "<";
   
   
   function ">" (left, right : sql_enumeration) return boolean_with_unknown is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value > right. value then
         return true;
      else
         return false;
      end if;
   end ">";
   
   
   function "<=" (left, right : sql_enumeration) return boolean_with_unknown 
   is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value <= right. value then
         return true;
      else
         return false;
      end if;
   end "<=";
   
   
   function ">=" (left, right : sql_enumeration) return boolean_with_unknown 
   is
   begin 
      if left. is_null or else right. is_null then
         return unknown;
      elsif left. value >= right. value then
         return true;
      else
         return false;
      end if;
   end ">=";
   
   
   function is_null (value : sql_enumeration) return boolean is
   begin 
      return value. is_null;
   end;
   
   
   function not_null (value : sql_enumeration) return boolean is
   begin 
      return not value. is_null;
   end;
   
   
   function "=" (left, right : sql_enumeration) return boolean is
   -- This code is changed some from the Guidelines   
      --  Document to be more compact
    
   begin 
      if left. is_null or else right. is_null then
         return false;
      else
         return left. value = right. value;
      end if;
   end "=";
   
   
   function "<" (left, right : sql_enumeration) return boolean is
   begin 
      if left. is_null or else right. is_null then
         return false;
      else
         return left. value < right. value;
      end if;
   end "<";
   
   
   function ">" (left, right : sql_enumeration) return boolean is
   begin 
      if left. is_null or else right. is_null then
         return false;
      else
         return left. value > right. value;
      end if;
   end ">";
   
   
   function "<=" (left, right : sql_enumeration) return boolean is
   begin 
      if left. is_null or else right. is_null then
         return false;
      else
         return left. value <= right. value;
      end if;
   end "<=";
   
   
   function ">=" (left, right : sql_enumeration) return boolean is
   begin 
      if left. is_null or else right. is_null then
         return false;
      else
         return left. value >= right. value;
      end if;
   end ">=";
   
   
   function pred 
      (value : in sql_enumeration) 
      return sql_enumeration 
   is
   begin 
      if value. is_null then
         return null_sql_enumeration;
      else
         return (with_null (sql_enumeration_not_null'pred (value. value)));
      end if;
   end pred;
   
   
   function succ 
      (value : in sql_enumeration) 
      return sql_enumeration 
   is
   begin 
      if value. is_null then
         return null_sql_enumeration;
      else
         return (with_null (sql_enumeration_not_null'succ (value. value)));
      end if;
   end succ;
   
   
   function pos (value : in sql_enumeration) return integer is
   begin 
      if value. is_null then
         raise null_value_error;
      else
         return sql_enumeration_not_null'pos (value. value);
      end if;
   end pos;
   
   
   function image 
      (value : in sql_enumeration_not_null) 
      return sql_char_not_null 
   is
   begin 
      return to_sql_char_not_null (sql_enumeration_not_null'image (value));
   end image;
   
   
   function image 
      (value : in sql_enumeration) 
      return sql_char 
   is
   begin 
      if value. is_null then
         raise null_value_error;
      else
         return to_sql_char (sql_enumeration_not_null'image (value. value));
      end if;
   end image;
   
   
   function val (value : in integer) return sql_enumeration is
   begin 
      return (with_null (sql_enumeration_not_null'val (value)));
   end val;
   
   
   function value 
      (value : in sql_char_not_null) 
      return sql_enumeration_not_null 
   is
   begin 
      return (sql_enumeration_not_null'value (to_string (value)));
   end value;
   
   
   function value 
      (value : in sql_char) 
      return sql_enumeration 
   is
   begin 
      if is_null (value) then
         return null_sql_enumeration;
      else
         return 
            with_null (sql_enumeration_not_null'value (to_string (value)));
      end if;
   end value;
   
   
end sql_enumeration_pkg;