Ada Error No Selector

here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Ada compile error- no selector for type up vote 0 down vote favorite I am debugging some simulation software that has been written in two parts- one part using C++, and the other using Ada. On the GUI, there are a few variables displaying information about an entity as it moves from point A to point B, such as the Time To Go (time it will take to complete that leg of the journey given its current speed & any other factors, such as wind) and ETA. One of these values is incorrect. It seems that the value displayed is coming from part of the Ada code: --update the legETAValid attribute this.steeringData.legETAValid := newSteeringData.legTTGValid; I noticed on the above line, that an incorrect value is being passed to the variable that is being displayed on the GUI, so I changed the line to the vale that should be displayed: this.steeringData.legETAValid := newSteeringData.legETAValid; However, when I try to build and run this code, I get a compile error that says: "no selector "legETAValid" for type "SteeringData_record" defined at...." Having never used Ada before, I'm unsure what this compile error means... is it similar to an "undeclared identifier" in C/C++? I have tried doing a 'Find all references' on the variable, and there are other places in the project where it is being used, so I wouldn't have thought that it is an 'undeclared identifier'... What does this error mean? Edit 04/02/2015 @ 09:10 The variable is declared in a .ads file with the line: legETAValid : Boolean := false; compiler-errors ada share|improve this question edited Feb 4 '15 at 9:14 asked Feb 3 '15 at 16:30 someone2088 5621237 1 It may be declared, but not "visible". You need to "with" the (usually) package that declares it, and either "use" that package, or "use type" to make that type's operations visible, or fully qualify its name, as in C++ namespaces. How do the "other places" make it visible? Adding relevant declarations to the question may help get an answer. –Brian Drummond Feb 3 '15 at 18:14 1 What that should mean is that if you look at type “SteeringData_record" defined at ... there won’t be a component legET

here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Unable to access members of an Ada generic parameter up vote 5 down vote favorite I am trying to write http://stackoverflow.com/questions/28303944/ada-compile-error-no-selector-for-type a generic package and one of the operations required is to checksum the data records received over a bus. The record type will vary and it is a generic parameter. However any attempts to access the members of the generic parameter cause a compilation error. The error ... (Ada 95 GNAT 2009) file.adb:XX no selector "Data" for private type "The_Transfer_Type" defined at file.ads:YY The declaration... generic type The_Transfer_Type is private; SIZE : Integer; http://stackoverflow.com/questions/2338913/unable-to-access-members-of-an-ada-generic-parameter package CC_Test_Channel is function Checksum(Msg : The_Transfer_Type) return Integer; end package And the body ... function Checksum(Msg : The_Transfer_Type) return Integer is Sum : Integer := 0; begin -- calculate the checksum for i in 1 .. SIZE loop Sum := Sum + Integer(Msg.Data(i)); end loop; return Sum; end Checksum; ada share|improve this question asked Feb 26 '10 at 1:21 mat_geek 1,7471526 add a comment| 3 Answers 3 active oldest votes up vote 5 down vote accepted When you specify that a generic parameter is a private type, well, Ada assumes you mean it :-) I.e. you have no access to its components. Ada is not "duck typed", so it's irrelevant whether or not you know that an instantiating type might actually possess a particular field. (How would you expect your Checksum function to work if The_Transfer_Type parameter were instantiated with, say, Integer?) One way to address this is to also supply an accessor function as a parameter to the generic that will retrieve the data needed to, in this case, compute the checksum. E.g.: generic type The_Transfer_Type is private; with function Get_Checksummable_Data_Item (Msg : The_Transfer_Type; I : Integer) return Integer; SIZE : Integer; package CC_Test_Channel is function Checksum(Msg : The_Transfer_Type) return Integer; end CC_Test_Channel; The body is then: function Checksum(Msg : The_Transfer_Type) return Integer is Sum

the unit's body 2 Lambda calculus through generics 3 Compiler Messages 4 Universal integers 5 I/O 5.1 Text_IO Issues 6 Quirks 6.1 Stack Size 7 References 8 See also 8.1 Wikibook 8.2 Ada Reference Manual Full declaration of a type can be deferred to the unit's https://en.wikibooks.org/wiki/Ada_Programming/Tips body[edit] Often, you'll want to make changes to the internals of a private type. This, in http://computer-programming-forum.com/44-ada/9e40f6ba68a3c917.htm turn, will require the algorithms that act on it to be modified. If the type is completed in the unit specification, it is a pain to edit and recompile both files, even with an IDE, but it's something some programmers learn to live with. It turns out you don't have to. Nonchalantly mentioned in the ARM, and generally skipped over in tutorials, is the fact ada error that private types can be completed in the unit's body itself, making them much closer to the relevant code, and saving a recompile of the specification, as well as every unit depending on it. This may seem like a small thing, and, for small projects, it is. However, if you have one of those uncooperative types that requires dozens of tweaks, or if your dependence graph has much depth, the time and annoyance saved add up quickly. Also, this construction ada error no is very useful when coding a shared library, because it permits to change the implementation of the type while still providing a compatible ABI. Code sample: package Private_And_Body is type Private_Type is limited private; -- Operations... private type Body_Type; -- incomplete type declaration completed in the body type Private_Type is access Body_Type; end Private_And_Body; The type in the public part is an access to the hidden type. This has the drawback that memory management has to be provided by the package implementation. That is the reason why Private_Type is a limited type, the client will not be allowed to copy the access values, in order to prevent dangling references. Normally, the full type definition has to be given in the specification because the compiler has to know how much place to allocate to objects in order to produce code using this type. And the astute reader will note that also in this case the full type definition is given for Private_Type: it is an access to some other (albeit incomplete) type, and the size of an access value is known. This is why the full type definition of Body_Type can be moved to the body. The construction centering around Private_Type is sometimes called an opaque pointer. Lambda calculus through generics[edit] Suppose you've decided to roll your own set type. You can add things to it, remove things from it, and you want to let a user apply some arbitrary functi

base type like this: ... type Base is tagged private; ... type Base is tagged record AAA: Integer:=1; end record; and a child type like this type Child is new Base with private; .... type Child is new Base with record BBB: Integer:=5; end record; The problem is that the following is not working: procedure Test(Ch: in Child) is begin Put(Ch.AAA); --<- This line has an error, it says no selector AAA for type Child Put(Ch.BBB); end Test; The procedure Test is declared in the same package as the type Child and defined at the package's Body. The error is becouse AAA is not part of Child. Why is that ? I thought that Child would contain AAA and BBB, and not only BBB... -- Papastefanos Serafeim Tue, 27 Dec 2005 04:56:23 GMT tmo..#2 / 9 Problems with tagged records and inheritance Quote:> The error is becouse AAA is not part of Child. > Why is that ? I thought that Child would contain > AAA and BBB, and not only BBB... But you said: >type Base is tagged private; so the makeup of Base is private, as you requested, and not visible to Child. Tue, 27 Dec 2005 06:15:45 GMT Robert I. Eachu#3 / 9 Problems with tagged records and inheritance Quote: > I have using a base type like this: > ... > type Base is tagged private; > ... -- Foot, bullet, shoot. Quote:> type Base is tagged record > AAA: Integer:=1; > end record; > and a child type like this > type Child is new Base with private; > .... > type Child is new Base with record > BBB: Integer:=5; > end record; > The problem is that the following is not working: > procedure Test(Ch: in Child) is > begin > Put(Ch.AAA); --<- This line has an error, it says no selector AAA for > type Child > Put(Ch.BBB); > end Test; > The procedure Test is declared in the same package > as the type Child and defined at the package's Body. Why would you expect this to work? You explicitly limited the knowledge of AAA to within the package where Base is declared, and in its childred. You can "fix" the problem by adding an inquiry function to the package containing Base: Pu