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  • Parameter mismatches definition

    Greetings! I just installed PowerBASIC. This is my first post. When I compiled the following code, I got the message: "Parameter mismatches definition". The compiler indicated that the problem is with the instruction:
    xx = STR$(AddOneDbl,8). Your help will be greatly appreciated. May you have a blessed day.

    Sincerely,

    Michael Fitzpatrick

    Code:
     
    FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYVAL x AS DOUBLE) EXPORT AS DOUBLE
      AddOneDbl = x + 1.0
    DIM XX AS DOUBLE
     
      xx = STR$(AddOneDbl,8)
      MSGBOX "Current value of XX is: " & xx
    END FUNCTION
    Greetings again. I fiddled around with the above code (without finding my error), and got something strange(to me) which compiled without errors:

    Code:
     FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYVAL x AS DOUBLE) EXPORT AS DOUBLE
    AddOneDbl = x + 1.0
    DIM XX AS DOUBLE
    DIM y AS DOUBLE
     
    xx = 5.0
    y = STR$(xx,8) > "tree"
     
    END FUNCTION
    I would have thought that there would be a type mismatch at the instruction: y = STR$(xx,8) > "tree"
    but the code compiled without error. Why would there be no errors in the compile of the function AddOneDbl? Thanks again.
    Michael Fitzpatrick
    Member
    Last edited by Michael Fitzpatrick; 25 Mar 2009, 02:17 AM. Reason: A strange (to me) compile

  • #2
    Looks like you need to change:

    dim xx as double

    to

    dim xx as string

    Welcome to the board!!!
    There are no atheists in a fox hole or the morning of a math test.
    If my flag offends you, I'll help you pack.

    Comment


    • #3
      Code:
      #COMPILE EXE
      
      #DIM ALL
      
      FUNCTION PBMAIN () AS LONG
      DIM xx AS DOUBLE
      
      
        xx = AddOneDbl(8)
        MSGBOX "Current value of XX is: " & STR$(xx)
      
      
      END FUNCTION
      FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYREF x AS DOUBLE)AS DOUBLE
        FUNCTION = x + 1.0
        END FUNCTION
      This code seems to work. The function needs function /end function outside the of the calling main code. The function will return a double value, so I showed it in the message box with str$(xx)

      Welcome to the PB forums. I don't know much technical stuff, but I have used PB win for several years now. I hope this helps

      John Tate
      John Tate
      Member
      Last edited by John Tate; 25 Mar 2009, 02:29 AM. Reason: edit the ending code tag

      Comment


      • #4
        I would have thought that there would be a type mismatch at the instruction: y = STR$(xx,8) > "tree"
        It's not a type mismatch because STR$(xx,8) > "tree" is evaluated as a boolian true/false expression, in this case, 0, which is valid for a DOUBLE. That is: is " 5" > "tree"? " " is less than "t" so no, it isn't greater, therefore the value returned is 0.

        Comment


        • #5
          Code:
          FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYVAL x AS DOUBLE) EXPORT AS DOUBLE
            AddOneDbl = x + 1.0
          DIM XX AS DOUBLE
           
            xx = STR$(AddOneDbl,8)
            MSGBOX "Current value of XX is: " & xx
          END FUNCTION
          The problem here in addition to Mel's point, is that you are calling the AddOneDbl function, so it needs its parameter. Also you are calling it recursively ie. the function is calling itself, and would result an infinite loop. Probably it would GPF before it got to infinity.

          So... this compiles, but I wouldn't recommend executing it:
          Code:
          FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYVAL x AS DOUBLE) EXPORT AS DOUBLE
            AddOneDbl = x + 1.0
          DIM XX AS STRING
           
            xx = STR$(AddOneDbl(99),8)    'I added 99 as the parameter
            MSGBOX "Current value of XX is: " & xx
          END FUNCTION

          Comment


          • #6
            >xx = STR$(AddOneDbl,8)

            Simple explanation:

            The function AddOneDbl expects exactly one parameter; parameters are passed to functions in parens; this code does not provide a param in parens, that is, passes zero parameters. Zero parameters passed vs one parameter expected = parameter mismatch.
            Michael Mattias
            Tal Systems (retired)
            Port Washington WI USA
            [email protected]
            http://www.talsystems.com

            Comment


            • #7
              FWIW, you will get the same "parameter mismatch" error by passing either a wrong datatype or a wrong number of parameters. (You can get a wrong number of parameters simply by typing a spurious comma)

              A long time ago I sent in a NFS to separate these into separate errors, "Parameter Data Type mismatch" and "Incorrect number of parameters" but I guess that has not yet bubbled up into production.

              MCM
              Michael Mattias
              Tal Systems (retired)
              Port Washington WI USA
              [email protected]
              http://www.talsystems.com

              Comment


              • #8
                Apparently function name cannot be treated as a variable

                Greetings! I thank everyone who contributed to this thread. After a bit of head scratching, I came to the conclusion that neither the function name nor FUNCTION can be treated as a variable--they can only be returned. What this function was doing was after compiling the instruction AddOneDbl = x, it was then trying to treat AddOneDbl(which is the function name) as a variable which PowerBASIC does not allow. With this insight I maodified my code as follows which compiles and executes without error:

                Code:
                 
                FUNCTION AddOneDbl ALIAS "AddOneDbl" (BYVAL x AS DOUBLE) EXPORT AS DOUBLE
                  x = x + 1.0
                  MSGBOX "Current value of x is: " & STR$(x)
                  AddOneDbl = x
                END FUNCTION
                Michael Fitzpatrick
                Member
                Last edited by Michael Fitzpatrick; 25 Mar 2009, 11:54 AM. Reason: typo

                Comment


                • #9
                  I came to the conclusion that neither the function name nor FUNCTION can be treated as a variable
                  ???

                  Functions DO act just like variables in expresssions in assignments, except if the function requires parameters they must be supplied:
                  Code:
                    LOCAL Z AS DOUBLE 
                  
                    LET  Z  =   AddOneDouble(2#) + AddOneDouble (2#) 
                    PRINT       USING$ ("This better equal 4 : " #.##",  Z)

                  FWIW, I always use "FUNCTION=<returnval>" in lieu of "<functionname>=<returnval>"

                  Maybe that's just style, but if helps me find what the function is supposed to be returning when I have to debug it.

                  MCM
                  Michael Mattias
                  Tal Systems (retired)
                  Port Washington WI USA
                  [email protected]
                  http://www.talsystems.com

                  Comment

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