type, class, object

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  • Michael
    #1

    type, class, object

    Hi,

    I could understand the difference between class and object. However, I
    could find out a good definiton of type. how to understand the
    relaitonship between type, class, and object? Thanks!

    Michael

    Tags: None
    • Victor Bazarov
      #2
      Re: type, class, object

      Michael wrote:
      I could understand the difference between class and object. However, I
      could find out a good definiton of type. how to understand the
      relaitonship between type, class, and object? Thanks!
      'class' is a user-defined type (UDT, a very common TLA in OOP). A type
      is a "kind" of objects, definiting common traits of all *instances* of
      that type ("objects"). Types in C++ are characterized by the name and
      the *definition*. Types in C++ consist of built-in and user-defined.
      The definition of a UDT contains *declarations*, which describe the
      representation and the behaviour of the instances of the UDT. The
      representation and the behaviour of built-in types is defined in the
      Standard.

      V
      --
      Please remove capital 'A's when replying by e-mail
      I do not respond to top-posted replies, please don't ask


        Comment

        • Michael
          #3
          Re: type, class, object


          Victor Bazarov wrote:
          'class' is a user-defined type (UDT, a very common TLA in OOP). A type
          is a "kind" of objects, definiting common traits of all *instances* of
          that type ("objects"). Types in C++ are characterized by the name and
          the *definition*. Types in C++ consist of built-in and user-defined.
          The definition of a UDT contains *declarations*, which describe the
          representation and the behaviour of the instances of the UDT. The
          representation and the behaviour of built-in types is defined in the
          Standard.
          >
          Could you please take an example for me to better understand it?

            Comment

            • Michael
              #4
              Re: type, class, object


              Victor Bazarov wrote:
              Michael wrote:
              I could understand the difference between class and object. However, I
              could find out a good definiton of type. how to understand the
              relaitonship between type, class, and object? Thanks!
              >
              'class' is a user-defined type (UDT, a very common TLA in OOP). A type
              is a "kind" of objects, definiting common traits of all *instances* of
              that type ("objects"). Types in C++ are characterized by the name and
              the *definition*. Types in C++ consist of built-in and user-defined.
              The definition of a UDT contains *declarations*, which describe the
              representation and the behaviour of the instances of the UDT. The
              representation and the behaviour of built-in types is defined in the
              Standard.
              I would think of type as "Class". Is thar right? There is no difference
              to call "Class" or "Type".

                Comment

                • Pierre Barbier de Reuille
                  #5
                  Re: type, class, object

                  Michael wrote:
                  Hi,
                  >
                  I could understand the difference between class and object. However, I
                  could find out a good definiton of type. how to understand the
                  relaitonship between type, class, and object? Thanks!
                  >
                  Michael
                  >
                  Well, in C++ : the types *include* the classes and objects are instances
                  of classes. Some types that are not classes :

                  C-like types : int, char, float
                  Function pointers types : int (*)(int,int)
                  Method pointers types : int (MyClass::*)(in t,int)
                  Other pointers type : int*, MyClass*

                  Pierre

                    Comment

                    • Victor Bazarov
                      #6
                      Re: type, class, object

                      Michael wrote:
                      Victor Bazarov wrote:
                      >Michael wrote:
                      >>I could understand the difference between class and object.
                      >>However, I could find out a good definiton of type. how to
                      >>understand the relaitonship between type, class, and object? Thanks!
                      >>
                      >'class' is a user-defined type (UDT, a very common TLA in OOP). A
                      >type is a "kind" of objects, definiting common traits of all
                      >*instances* of that type ("objects"). Types in C++ are
                      >characterize d by the name and the *definition*. Types in C++
                      >consist of built-in and user-defined. The definition of a UDT
                      >contains *declarations*, which describe the representation and the
                      >behaviour of the instances of the UDT. The representation and the
                      >behaviour of built-in types is defined in the Standard.
                      >
                      I would think of type as "Class". Is thar right?
                      No, in C++ it's vice-versa. Did you actually read what I posted?

                      Types consist of built-in and user-defined. "class" is a user-defined
                      type. So class is a type. A 'type' is a wider concept than a 'class',
                      at least in C++.
                      There is no
                      difference to call "Class" or "Type".
                      In some circumstances there is. You can derive from a class, you
                      cannot, generally speaking, derive from a type.

                      V
                      --
                      Please remove capital 'A's when replying by e-mail
                      I do not respond to top-posted replies, please don't ask


                        Comment

                        • Howard
                          #7
                          Re: type, class, object


                          "Michael" <michaelnx@gmai l.comwrote in message
                          news:1154540707 .145109.249480@ i3g2000cwc.goog legroups.com...
                          >
                          Victor Bazarov wrote:
                          >Michael wrote:
                          I could understand the difference between class and object. However, I
                          could find out a good definiton of type. how to understand the
                          relaitonship between type, class, and object? Thanks!
                          >>
                          >'class' is a user-defined type (UDT, a very common TLA in OOP). A type
                          >is a "kind" of objects, definiting common traits of all *instances* of
                          >that type ("objects"). Types in C++ are characterized by the name and
                          >the *definition*. Types in C++ consist of built-in and user-defined.
                          >The definition of a UDT contains *declarations*, which describe the
                          >representati on and the behaviour of the instances of the UDT. The
                          >representati on and the behaviour of built-in types is defined in the
                          >Standard.
                          >
                          I would think of type as "Class". Is thar right? There is no difference
                          to call "Class" or "Type".
                          >
                          Where do you get the word "Class" from? Are you referring to the keyword
                          "class", which denotes one kind of user-defined-type? (The other being the
                          keyword "struct".)

                          The concept of "type" in C++ means, basically, "what kind of thing is
                          this?". So, some examples of types are: int, char, and unsigned long.
                          These are built-in types, already defined in the language for you.

                          If you have a class definition like this:

                          class MyClass { /* member stuff here */ };

                          ....then you have a user-defined type (or UDT), whose type is MyClass.

                          Likewise, the definition

                          struct MyStruct { /* member stuff here */ };

                          ....defines a UDT, whose type is MyStruct.

                          (Sometimes in OOP, the terms "UDT" and "class" are used interchangeably , but
                          to me that can be confusing, since in C++ we also have UDTs which are
                          struct's, as I've shown.)

                          Given the above definitions,

                          MyClass aMyClassInstanc e;

                          ....declares a variable called aMyClassInstanc e, whose type is MyClass, and

                          MyStruct aMyStructInstan ce;

                          ....declares a variable called aMyStructInstan ce, whose type is MyStruct, and

                          -Howard




                            Comment

                            • Default User
                              #8
                              Re: type, class, object

                              Howard wrote:
                              >
                              "Michael" <michaelnx@gmai l.comwrote in message
                              news:1154540707 .145109.249480@ i3g2000cwc.goog legroups.com...
                              I would think of type as "Class". Is thar right? There is no
                              difference to call "Class" or "Type".
                              >
                              Where do you get the word "Class" from? Are you referring to the
                              keyword "class", which denotes one kind of user-defined-type? (The
                              other being the keyword "struct".)
                              Poor ol' "union", forsaken again.




                              Brian

                                Comment

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