I have a problem with my in Xtext created Datatypes. The problems lies within this function:
«FOR e: bla.EAllAttributes»
«e.EType.name» «e.name»;
«ENDFOR»
This for-loop just returns EInt or EString for e.EType.name. But i need the terminal rules/datatypes created in my DSL like double, boolean and so on. It seems every terminal rule with a string expression is returned as EString and rules with only numbers are returned as EInt. Enumerations are correctly returned though...
Thank you in advance for your help.
In the manual there is a section explaining your issue. See "Reference Documentation", "The Grammar Language", "The Syntax", "Rules", "Terminal Rules", "Return Types":
Each terminal rule returns an atomic value (an Ecore EDataType). By default, it's assumed that an instance of ecore::EString) should be returned. However, if you want to provide a different type you can specify it.
That section also outlines the grammar changes and registration of the value converters you must provide.
There is also another sections "Data Type Rules" which basically says that it is the same as in the "terminal rule" case and forwards you to the "Value converter" section.
Related
Let's assume a FIX field is of type MULTIPLECHARVALUE or MULTIPLESTRINGVALUE, and the enumerated values defined for the field are A, B, C and D. I know that "A C D" is a legal value for this field, but is it legal for a value to be repeated in the field? For example, is "A C C D" legal? If so, what are its semantics?
I can think of three possibilities:
"A C C D" is an invalid value because C is repeated.
"A C C D" is valid and semantically the same as "A C D". In other words, set semantics are intended.
"A C C D" is valid and has multiset/bag semantics.
Unfortunately, I cannot find any clear definition of the intended semantics of MULTIPLECHARVALUE and MULTIPLESTRINGVALUE in FIX specification documents.
The FIX50SP2 spec does not answer your question, so I can only conclude that any of the three interpretations could be considered valid.
Like so may questions with FIX, the true answer is dependent upon the counterparty you are communicating with.
So my answer is:
if you are client app, ask your counterparty what they want (or check their docs).
if you are the server app, you get to decide. Your docs should tell your clients how to act.
If it helps, the QuickFIX/n engine treats MultipleCharValue/MultipleStringValue fields as strings, and leaves it to the application code to parse out the individual values. Thus, it's easy for a developer to support any of the interpretations, or even different interpretations for different fields. (I suspect the other QuickFIX language implementations are the same.)
The definition of MultipleValueString field is a string field containing one or more space delimited values. I haven't got the official spec, but there are few locations where this definition can be found:
https://www.onixs.biz/fix-dictionary/4.2/index.html#MultipleValueString (I know onixs.biz to be very faithful to the standard specification)
String field (see definition of "String" above) containing one or more space delimited values.
https://aj-sometechnicalitiesoflife.blogspot.com/2010/04/fix-protocol-interview-questions.html
12. What is MultipleValueString data type? [...]
String field containing one or more space delimited values.
This leaves it up to a specific field of this type whether multiples are allowed or not, though I suspect only a few if any would need to have multiples allowed. As far as I can tell, the FIX specification deliberately leaves this open.
E.g. for ExecInst<18> it would be silly to specify the same instruction multiple times. I would also suspect each and every implementation to behave differently (for instance one ignoring duplicates, another balking with an error/rejection).
I was reading the manual for the programming language Maude and I found some keyword sort. The description of it (here) is:
sorts, giving names for the types of data,
does someone know what it means? Is it just defining a type?
sort is "a type definition". In Maude, all types are defining an order-sorted signature. However, the sort will be empty until you declare its signature by means of op.
Under Window > Preferences > General > Search, there is the option Ignore potential matches
What does it do? Whether I activate it or not, I never see a difference.
Is it an option that only makes sense for Java development (which I never do, but I do develop in C, Python and PHP using Eclipse)?
See bug 127442 for examples: depending on what you are searching (a class, a method, ...), the Search engine can find instances which could match (but it cannot say for certain).
Those instances are marked "POTENTIAL_MATCH":
A method with different number of parameters is not a potential match.
(see bug 97322 )
A potential match is a match where the resolution failed (e.g. the method binding is null).
If the user searches for "foo(String)" (without qualifying String), then "foo(java.lang.String)" and "foo(p.String)" are both exact matches.
For the .class file case, I think we can only have potential matches in the case of the missing type case (see bug 196200), i.e if the .class file was compiled and some types it references were missing.
A current example of potential match misbehavior is found in bug 382778:
I have a public static void method printIt(String name).
When I open its call hierarchy, some callers are missing.
I am guessing the callers are missing because java search marks them as potential instead of exact matches for the printIt(String) reference.
The following code is sometimes marked as potential, and sometimes exact:
// Listing 1
PublicInterface2 impl2 = new Impl2("Name Broken");
Static.printIt(impl2.getName());
When the search result is marked potential, the caller is missing from the printIt() call hierarchy.
PublicInterface2 is an empty public interface which extends PackageInterface2Getters.
PackageInterface2Getters is an empty default-scoped interface which extends PackageInterface1Getters.
PackageInterface1Getters is a default-scoped interface which declares String getName().
So impl2.getName() above returns a String.
There are some problems reported which I guess make the matches be marked as potential:
...
Filename : \D:\workspace\eclipse\_runtimes\jdt\call-hierarchy-bug\src\main\PublicInterface2.java
COMPILED type(s)
2 PROBLEM(s) detected
- Pb(2) PackageInterface1Getters cannot be resolved to a type
- Pb(327) The hierarchy of the type PublicInterface2 is inconsistent
Turns out that:
The compiler asks the "NameEnvironment" to get the type information of any dependent type.
Search has it's own NameEnvironment implementation in JavaSearchNameEnvironment and it is not looking for secondary types.
This is bad and it is surprising that we haven't run into this problem until now.
In Eclipse Luna (Service Release 1 (4.4.1)) I searched just for references to this Java method:
merge(DashboardConfigurationModel template, DashboardModel custom)
It returns two references. One of these calls to the merge() method passes in a DashboardConfigurationModel and a DashboardModel, as befits the method signature. This is a match all right!
The other reference to a merge() method passes in a String and a Map. It is marked in Eclipse as a "potential match" but in my mind, since the argument types don't match, this has zero potential to be a match.
I then checked Ignore potential matches, did the search again, and this noise went away.
Which of these two definitions is correct?
Statically typed - Type matching is checked at compile time (and therefore can only be applied to compiled languages)
Dynamically typed - Type matching is checked at run time, or not at all. (this term can be applied to compiled or interpreted languages)
Statically typed - Types are assigned to variables, so that I would say 'x is of type int'.
Dynamically typed - types are assigned to values (if at all), so that I would say 'x is holding an int'
By this definition, static or dynamic typing is not tied to compiled or interpreted languages.
Which is correct, or is neither one quite right?
Which is correct, or is neither one quite right?
The first pair of definitions are closer but not quite right.
Statically typed - Type matching is checked at compile time (and therefore can only be applied to compiled languages)
This is tricky. I think if a language were interpreted but did type checking before execution began then it would still be statically typed. The OCaml REPL is almost an example of this except it technically compiles (and type checks) source code into its own byte code and then interprets the byte code.
Dynamically typed - Type matching is checked at run time, or not at all.
Rather:
Dynamically typed - Type checking is done at run time.
Untyped - Type checking is not done.
Statically typed - Types are assigned to variables, so that I would say 'x is of type int'.
Dynamically typed - types are assigned to values (if at all), so that I would say 'x is holding an int'
Variables are irrelevant. Although you only see types explicitly in the source code of many statically typed languages at variable and function definitions all of the subexpressions also have static types. For example, "foo" + 3 is usually a static type error because you cannot add a string to an int but there is no variable involved.
One helpful way to look at the word static is this: static properties are those that hold for all possible executions of the program on all possible inputs. Then you can look at any given language or type system and consider which static properties can it verify, for example:
JavaScript: no segfaults/memory errors
Java/C#/F#: if a program compiled and a variable had a type T, then the variable only holds values of this type - in all executions. But, sadly, reference types also admit null as a value - the billion dollar mistake.
ML has no null, making the above guarantee stronger
Haskell can verify statements about side effects, for example a property such as "this program does not print anything on stdout"
Coq also verifies termination - "this program terminates on all inputs"
How much do you want to verify, this depends on taste and the problem at hand. All magic (verification) comes at price.
If you have never ever seen ML before, do give it a try. At least give 5 minutes of attention to Yaron Minsky's talk. It can change your life as a programmer.
The second is a better definition in my eyes, assuming you're not looking for an explanation as to why or how things work.
Better again would be to say that
Static typing gives variables an EXPLICIT type that CANNOT change
Dynamic typing gives variables an IMPLICIT type that CAN change
I like the latter definition. Consider the type checking when casting from a base class to a derived class in object oriented languages like Java or C++ which fits the second definition and not the first. It's a compiled language with (optional) dynamic type checking.
I'm currently experimenting with using OCaml and GTK together (using the lablgtk bindings). However, the documentation isn't the best, and while I can work out how to use most of the features, I'm stuck with changing notebook pages (switching to a different tab).
I have found the function that I need to use, but I don't know how to use it. The documentation seems to suggest that it is in a sub-module of GtkPackProps.Notebook, but I don't know how to call this.
Also, this function has a type signature different to any I have seen before.
val switch_page : ([> `notebook ], Gpointer.boxed option -> int -> unit) GtkSignal.t
I think it returns a GtkSignal.t, but I have no idea how to pass the first parameter to the function (the whole part in brackets).
Has anyone got some sample code showing how to change the notebook page, or can perhaps give me some tips on how to do this?
What you have found is not a function but the signal. The functional type you see in its type is the type of the callback that will be called when the page switch happen, but won't cause it.
by the way the type of switch_page is read as: a signal (GtkSignal.t) raised by notebook [> `notebook ], whose callbacks have type Gpointer.boxed option -> int -> unit
Generally speaking, with lablgtk, you'd better stay away of the Gtk* low level modules, and use tge G[A-Z] higher level module. Those module API look like the C Gtk one, and I always use the main Gtk doc to help myself.
In your case you want to use the GPack.notebook object and its goto_page method.
You've found a polymorphic variant; they're described in the manual in Section 4.2, and the typing rules always break my head. I believe what the signature says is that the function switch_page expects as argument a GtkSignal.t, which is an abstraction parameterized by two types:
The first type parameter,
[> `notebook]
includes as values any polymorphic variant including notebook (that's what the greater-than means).
The second type parameter is an ordinary function.
If I'm reading the documentation for GtkSignal.t correctly, it's not a function at all; it's a record with three fields:
name is a string.
classe is a polymorphic variant which could be ``notebook` or something else.
marshaller is a marshaller for the function type Gpointer.boxed option -> int -> unit.
I hope this helps. If you have more trouble, section 4.2 of the manual, on polymorphic variants, might sort you out.