Ramping up on Dart and wondering why some keywords are preceded by an '#', such as #required and #override? Would obviously be cleaner if the '#' was omitted, so I'm sure its necessary, just wondering why.
EDIT
Thanks to the answer below, I see these are called annotations. I'm still confused why annotations are preceded by '#'. I come from the c++ world where "override" is a specifier and part of the language (so not proceeded by a special character). Are annotations not officially part of the dart language? I.e., why isn't "override" and "required" added to the language without the '#'?
Keywords that starts with the at sign # are called annotation. Annotations provide semantic information that tools can use to provide a better user experience. For example, an IDE might not autocomplete the name of a function that's been marked #deprecated, or it might display the function's name differently.
Related
The value side of attributes in HTML were very unreadable, too dark, making it especially hard to disseminate between class names in HTML, when using the dark theme on VS Code.
How do I change it to make reading more comfortable?
p.s. My "Tags" are very limited due to rep, but I'm so sure others have this question.
Here is how to accomplish this particular task.
Introducing [me to] a very useful tool: Inspect Editor Tokens and Scopes
Put cursor in, in this case, a quoted value string.
CNTL + SHIFT + P (open command palette).
Find "Developer: Inspect Editor Tokens and Scopes"
Note the textmate scope(s).
Use property: "editor.tokenColorCustomizations" → "textMateRules" to add new rule.
While I'm doing this directly on values in the JSON of settings - and changing quotes there at a high level, this also works with inheritance, so string.quoted.double.html would override the example shown in this screenshot (which applies to ALL double quoted strings), when editing HTML files. I find this useful for making my lint rules standout too.
I need to parse something during the runtime of my eclipse plugin (created with Xtext) which would then be treated as if the user has typed it in but without actually popping up and beeing visible for the user as an input of himself.
For exmample I have this input:
for "i" from 1 to 3 do {};
My problem woth this input is that the variable i is not declared as a normal declaration with a "=" but I need the parser to tell that it is one. So I want to let the parser parse
i = 1;
so it recognizes it as a normal declaration and allows cross-references to it.
Greeting Krzmbrzl
EDIT:
All in all the thing I want is to add a statement i=1; to the AST
I just want to have eclipse support for an existing language so I'm not writing an interpreter nor a generator. The problem is that when I have a for-loop like above the actual interpreter of that language declares a variable i (or however it's named in the loop header) and therefore this variable is available in the loop body. In my case my parser doesn't recognise i as a variable because it only knows that a declaration is done via "=" so I can't use i in the loop body (if I try so I get the error that the declaration i cannot be resolved). This is why I want to add this declaration manually when such a loop is created. I don't need to worry about any compiling or interpreting difficulties because I don't do this myself. As I already said I just want to have all the cool eclipse features for this language.
Ok, now I understand your problem. It is still no good idea to add any element to the AST to resolve any cross reference! You don't do that! Instead you should try to refactor your grammar in a way that "i" in for "i" from ... is a compatible declaration of a variable. There are several tricks to do that. Have you completely read the Xtext documentation? Have also read the Xtext book? Both documents tell a lot about how to make Xtext do things you will not expect.
Anyway, two tricks I often use are:
Introduce an unused, abstract Parser Rule which you can then use as destination of a cross reference, but which is never used as an attribute (containment reference).
AbstractDecl:
VarDecl | ForVarDecl;
VarDecl:
name=ID ...;
ForVarDecl:
'"' name=ID '"';
For:
'for' decl=ForVarDecl 'from' from=INT 'to' to=INT 'do' block=Block;
...
StatementWithCR:
ref=[AbstractDecl] ...;
Define any ParserRule, which returns an other type.
ForDecl returns VarDecl:
'"' name=ID '"';
If you would post the grammar which corresponds to this specific problem, we could develop a solution which is safe. Adding anything to the AST during live processing content of the editor will lead to a faulty state which can destroy your document.
I find Erlang's module arity import /n where n is the number of arguments rather bizarre.
In Java and various other languages you can do something like:
import static com.stuff.Blah.myFunction;
Which will import all overloaded Blay.myFunction(..) regardless of parameters.
Besides I guess being explicit why did the language designers decide this was a good idea (I'm not trying to criticize the language... just curious)?
Does it have to do with code swapping?
Or does it have to do with hiding guard methods for recursion? If so why not allow arity on export but no need for arity on import?
Why would I want to be that explicit? That is import the two argument function but not the the three argument of myFunction?
You should be aware of what importing functions in Erlang really does. It is a pure textual transformation. If I do an -import(foo, [bar/1,baz/2]). it means that when I write a call like bar(5) or baz(a, 3) the compiler transforms these to foo:bar(5) and foo:baz(a, 3). That is all it does, nothing else. It doesn't check anything:
It doesn't check if the module foo contains the functions bar/1 or baz/2.
It doesn't even check if the module foo exists.
Really all it does is hide that you are calling a function in another module. That is why the recommendation from experienced Erlangers is "don't use it". It was a mistake. Unfortunately it is much easier to add stupid things than to get rid of them so we were never able to remove it.
"Does it have to do with code swapping?"
Yes, sort of. The unit of all code handling in Erlang is the module. So you compile modules, load modules, purge and delete modules. This means that there are no inter-module dependencies at all in the system and the compiler makes no assumptions about other modules when it is compiling a module. No assumptions are made that the environment in which a module is compiled will be the same in which it is run. That is why it is at runtime the system checks whether the function you are trying to call in another exists, or even if the module itself exists. That is why the import was a purely textual transformation.
Erlang was originally developed in Prolog.
In Prolog, the arity adds additional meaning to what you consider to be the 'arguments, as I understand from a function' in a procedural programming language. But that model does not apply here.
The so-called clauses 'married(X,Y).' and 'married(X,Y,Z).' imply a different kind of relationship 'married', which can be declared as married/2 and married/3.
In procedural programming, 'add(a,b)' or 'add(a,b,c)' are intended to generate the addition of a different number of arguments. That's not immediately the case in Prolog, where it is possible to have the relationship 'a and b, added' or 'a, b and c, added' mean something else. Needless to say, Prolog allows you to declare 'add' as you would expect a function would do. But it allows for more. More available meaning, means more need to control it.
And as in any module system, selecting what you want to expose to external clients makes sense: hence the declaration of arity.
Does it have to do with code swapping?
Kind of. The modules in Erlang are compiled separately (which is part of what allows code swapping), unlike Java classes, so the compiler doesn't know how many versions of the imported function with different arities exist. It could assume that all calls of a function with the given name come from the same module, of course, but the designers likely decided it wasn't particularly useful.
In fact, you rarely want to use imports at all, at least in my experience, just as you rarely use static imports in Java. Just write module:function, like Class.staticMethod.
Or does it have to do with hiding guard methods for recursion?
No, since not importing functions doesn't hide them in any way.
I need help importing a library to Xamarin. I included the library and inserted it into a new folder named BarcodeScanner, and the name of the library is libBarcodeScanner.a.
gcc_flags "-L${ProjectDir} -lBarcodeScanner -force_load ${ProjectDir}/libBarcodeScanner.a”
But it shows an error:
Error: Could not parse additional mtouch arguments: No matching quote found.
What should i do ?
Do i need to create a binding project to use a library like BarcodeScanner ?
Error: Could not parse additional mtouch arguments: No matching quote found.
That does not look like a Xamarin.iOS (mtouch) error message. Those start with a MT prefix followed by 4 numbers, e.g. MT2001. Could it be Xamarin Studio giving you this error ?
What should i do ?
Review the flags: are they identical to what's pasted above ?
No matching quote found. makes is sound there's an extra quote in there. Maybe one of the " is wrong (e.g. a autocorrection giving you a smart quote) ?
Or maybe your project directory (replaced from ${ProjectDir} contains a quote character ?
Also can you edit your question to add which version of Xamarin Studio you're using ?
Do i need to create a binding project to use a library like BarcodeScanner ?
No, but it's the preferred ways to link static libraries. Using a binding project removed the need to add Additional mtouch arguments inside every projects and every build configuration (e.g. Debug, Release...) of your applications.
I will answer my own question, maybe it will help someone. I declared in my MainController that i needed:
using MonoTouch.CoreVideo;
using MonoTouch.CoreMedia;
using MonoTouch.CoreGraphics;
using MonoTouch.CoreFoundation;
And after that i referenced only the static library with:
-gcc_flags "-L${ProjectDir} -lBarcodeScanner -force_load ${ProjectDir}/libBarcodeScanner.a"
#poupou's "maybe" was spot on, but I'll be pedantic and explain exactly.
Look closely at this line I just quoted from your original question. I've marked it down using code (four spaces prefix per line), and broke it into two lines. Nothing else has been changed. Hopefully the error should be obvious now:
- gcc_flags "-L${ProjectDir} -lBarcodeScanner
-force_load ${ProjectDir}/libBarcodeScanner.a”
Essentially, you used different types of double quotes. The first double-quote character above is Unicode 0x0022, which is the regular Quotation Mark. The second double-quote character above is Unicode 0x8221, or Right Double Quotation Mark. It might be that you had copied & pasted all or part of the line above from a web page, rather than typing it in.
For command-line processing, mixing your styles of double quotes simply won't work. You'll need to use balanced regular quotation marks, as you wrote in your own answer just now (but might not have specifically noticed?) FWIW, the right- and left- variants of the quotation mark are usually used for word processing, web pages, etc. where the style aesthetic matters.
Since you didn't use code-markup when quoting that line originally (while I noticed you did, in your recently posted answer) it looks like Stack Overflow "helpfully" tried to render the quotes as similar in style, fooling us into looking elsewhere for the problem, when it was right in front of us.
Anyway, next time you get an error about mismatched quotes, I suggest you carefully check their type. If they look the least bit different, they may not be the right kind of quotes.
Does anyone know of a short cut to place my name and the date where the cursor is i.e.
//021208 DarkAxi0m
so i don't keep check what the date is when i'm adding comments.
Im using Delphi7, with CnPack And GExperts Installed.
I think it should be able to be done with one of those experts.
I use GExperts to do this, like so:
in the
GExperts\Configuration
Select the Editor Experts tab.
In the list of experts, select
Insert Date\Time
Click on the configuration, insert the desired text:
'//' ddmmyy 'DarkAxi0m: '
//021208 DarkAxi0m:
After, to insert your new Date name comment all you need to do is:
ctrl+alt+a
I setup most programmers at the job like that.
It is also simple to do with GExperts' Expand Macro Template (found in Editor Experts).
I use this expansion to insert yyyy-mm-dd at the current position:
%YEAR%-%MONTH%-%DAY%|
For a solution that will work in most applications under Windows, not only in Delphi, you can use Authotkey (free, autohotkey.com). One of its many features is the ability to expand strings that you type - typically used for autocorrecting typos.
I start all my shortcut strings with a semicolon, since it practically never leads strings I type in real life, so in your example, to insert a comment-date-username sequence, I would want to type semicolon, slash, slash:
;//
The Authotkey script (which you can put in an .ahk text file and add the file to Autostart) would look like this:
::;//:: ; this means: when I type ";//", do what follows
FormatTime, curDate,, yyyy-MM-dd ; the double comma is intended
SendInput // %curDate% %A_UserName% ; variable expansion
return
This produces the following output:
// 2008-12-05 moodforaday
AHK syntax is a little dense, but there is an extensive help file.
On edit: this script could be expanded to apply the correct comment syntax depending on the IDE you are working in at the moment. You would detect active window title, find a signature substring ("Delphi") and choose the proper comment character(s). This way you could type the same hotstring to insert your comment regardless of the current IDE or language. You can also use SendInput to position the caret the way Delphi templates do.
Never mind found one in CnPack/Soure Templates
Added the template
//%Date% DarkAxi0m
Note: i should look in the menus more closely
You might also look at the Live Templates feature, which can be scripted to do just what you want:
http://cc.codegear.com/Item/24990
Don't be put off by the name, it includes a template script to include the date, time, including the ability to format it as you want.
Here is a variation with GExperts (www.gexperts.org) that makes it easy to search for changes based on developer or date.
Example of output and comment:
//07.25.2009 (SLB20090725) - Added 3rd optional parameter.
Besides an easily readable date I can easy search for comments programmer, by year, year+month etc.)
For example I can search for (SLB200905 for any comments I logged in May of 2009.
To do:
Under the GExperts menu open Configuration... (at the bottom of the list) then select the Editor Experts tab.
Locate 'Insert Date/Time' and double click on it.
//mm.dd.yyyy '(ABC'yyyymmdd') -'
Where ABC is the programmers name, initials, id, or whatever.
Then use Ctrl-Alt-A when in Delphi's IDE to insert
This should work in any verison of Delphi supported by GExperts.