I am learning from the project angular2-rxjs-chat application ong github. In the code here there is a line of code given below:
threads[message.thread.id] = threads[message.thread.id] ||
message.thread;
where threads has earlier been defined on line 29 in the code as shown below:
let threads: {[key: string]: Thread} = {};
The comments in the code states that "store the message's thread in our acuuculator 'threads'. I need a little bit explanation of how does the assignment works on line 31 as on both sides of the assignment operator we have the same thing i.e., threads[message.thread.id]. If the statement on line 31 was like
(threads[message.thread.id] = message.thread;)
then I would explain it as a value is being assigned to a key in the map "threads". But I don't understand the full line.
This means if threads[message.thread.id] already has a value then keep it, otherwise set the value to meassage.thread.
If the part before || evaluates to a value that is truthy (not null, undefined, false, ...)then the part after||is not evaluated and the result from the part before||is returned otherwise the result from the expression after||` is returned.
You could also write it as
if(!threads[message.thread.id]) {
threads[message.thread.id] = message.thread;
}
Related
I'm trying to use SequenceReader<T> in .Net Core Preview 8 to parse Guacamole Protocol network traffic.
The traffic might look as follows:
5.error,14.some text here,1.0;
This is a single error instruction. There are 3 fields:
OpCode = error
Reason = some text here
Status = 0 (see Status Codes)
The fields are comma delimited (semi-colon terminated), but they also have the length prefixed on each field. I presume that's so that you could parse something like:
5.error,24.some, text, with, commas,1.0;
To produce Reason = some, text, with, commas.
Simple comma delimited parsing is simple enough to do (with or without SequenceReader). However, to utilise the length I've tried the following:
public static bool TryGetNextElement(this ref SerializationContext context, out ReadOnlySequence<byte> element)
{
element = default;
var start = context.Reader.Position;
if (!context.Reader.TryReadTo(out ReadOnlySequence<byte> lengthSlice, Utf8Bytes.Period, advancePastDelimiter: true))
return false;
if (!lengthSlice.TryGetInt(out var length))
return false;
context.Reader.Advance(length);
element = context.Reader.Sequence.Slice(start, context.Reader.Position);
return true;
}
Based on my understanding of the initial proposal, this should work, though also could be simplified I think because some of the methods in the proposal make life a bit easier than that which is available in .Net Core Preview 8.
However, the problem with this code is that the SequenceReader does not seem to Advance as I would expect. It's Position and Consumed properties remain unchanged when advancing, so the element I slice at the end is always an empty sequence.
What do I need to do in order to parse this protocol correctly?
I'm guessing that .Reader here is a property; this is important because SequenceReader<T> is a mutable struct, but every time you access .SomeProperty you are working with an isolated copy of the reader. It is fine to hide it behind a property, but you'd need to make sure you work with a local and then push back when complete, i.e.
var reader = context.Reader;
var start = reader.Position;
if (!reader.TryReadTo(out ReadOnlySequence<byte> lengthSlice,
Utf8Bytes.Period, advancePastDelimiter: true))
return false;
if (!lengthSlice.TryGetInt(out var length))
return false;
reader.Advance(length);
element = reader.Sequence.Slice(start, reader.Position);
context.Reader = reader; // update position
return true;
Note that a nice feature of this is that in the failure cases (return false), you won't have changed the state yet, because you've only been mutating your local standalone clone.
You could also consider a ref-return property for .Reader.
From a linter provider, I receive a Point compatible array(line, column) where the error occured. Now I would like to hightlight the word surrounding that point, basically the result one would get if that exact point was double-clicked in the editor. Something like
const range = textEditor.getWordAtPosition(point)
Is what I hoped for, but couldn't find in the documentation.
Thanks for your help!
After looking around for a while, there seems to be no API method for the given need. I ended up writing a small helper function based upon this answer:
function getWordAtPosition(line, pos) {
// Perform type conversions.
line = String(line);
pos = Number(pos) >>> 0;
// Search for the word's beginning and end.
const left = Math.max.apply(null, [/\((?=[^(]*$)/,/\)(?=[^)]*$)/, /\,(?=[^,]*$)/, /\[(?=[^[]*$)/, /\](?=[^]]*$)/, /\;(?=[^;]*$)/, /\.(?=[^.]*$)/, /\s(?=[^\s]*$)/].map(x => line.slice(0, pos).search(x))) + 1
let right = line.slice(pos).search(/\s|\(|\)|\,|\.|\[|\]|\;/)
// The last word in the string is a special case.
if (right < 0) {
right = line.length - 1
}
// Return the word, using the located bounds to extract it from the string.
return str.slice(left, right + pos)
}
Here, the beginning of the word is determined by the latest occurance of one of the characters (),.[]; or a blank.
The end of the word is determined by the same characters, however here the first occurance is taken as a delimeter.
Given the original context, the function can the be called using the API method ::lineTextForBufferRow and the desired postion (column) as follows:
const range = getWordAtPosition(textEditor.lineTextForBufferRow(bufferRow), 10)
EDIT: I accidentally misrepresented the problem when trying to pare-down the example code. A key part of my code is that I am attempting to sort the array after adding elements to it. The hang appears on sort, not insert. The following abstracted code will consistently hang:
<?=
local('a' = array)
#a->insert('test1' = map('a'='1'))
#a->insert('test2' = map('b'='2')) // comment-out to make work
#a->sort
#a
?>
I have a result set for which I want to insert a pair of values into an array for each unique key, as follows:
resultset(2) => {
records => {
if(!$logTypeClasses->contains(field('logTypeClass'))) => {
local(i) = pair(field('logTypeClass'), map('title' = field('logType'), 'class' = field('logTypeClass')))
log_critical(#i)
$logTypeClasses->insert(#i) // Lasso hangs on this line, will return if commented-out
}
}
}
Strangely, I cannot insert the #i local variable into thread variable without Lasso hanging. I never receive an error, and the page never returns. It just hangs indefinitely.
I do see the pairs logged correctly, which leads me to believe that the pair-generating syntax is correct.
I can make the code work as long as the value side of the pair is not a map with values. In other words, it works when the value side of the pair is a string, or even an empty map. As soon as I add key=value parameters to the map, it fails.
I must be missing something obvious. Any pointers? Thanks in advance for your time and consideration.
I can verify the bug with the basic code you sent with sorting. The question does arise how exactly one sorts pairs. I'm betting you want them sorted by the first element in the pair, but I could also see the claim that they should be sorted by last element in the pair (by values instead of by keys)
One thing that might work better is to keep it as a map of maps. If you need the sorted data for some reason, you could do map->keys->asArray->sort
Ex:
local(data) = map('test1' = map('a'=2,'b'=3))
#data->insert('test2' = map('c'=33, 'd'=42))
local(keys) = #data->keys->asArray
#keys->sort
#keys
Even better, if you're going to just iterate through a sorted set, you can just use a query expression:
local(data) = map('test1' = map('a'=2,'b'=3))
#data->insert('test2' = map('c'=33, 'd'=42))
with elm in #data->eachPair
let key = #elm->first
let value = #elm->second
order by #key
do { ... }
I doubt you problem is the pair with map construct per se.
This test code works as expected:
var(testcontainer = array)
inline(-database = 'mysql', -table = 'help_topic', -findall) => {
resultset(1) => {
records => {
if(!$testcontainer->contains(field('name'))) => {
local(i) = pair(field('name'), map('description' = field('description'), 'name' = field('name')))
$testcontainer->insert(#i)
}
}
}
}
$testcontainer
When Lasso hangs like that with no feedback and no immediate crash it is usually trapped in some kind of infinite loop. I'm speculating that it might have to do with Lasso using references whenever possible. Maybe some part of your code is using a reference that references itself. Or something.
EDIT: Forgot to mention that my programming language is C++, and my IDE is Qt Creator.
I don't understand why I am having trouble adding elements to a referenced vector of a map (i.e. sometimes it works and sometimes it fails).
For example:
class C_html4_tags {
public:
C_html4_tags();
//.......
typedef std::vector<S_html_attr_value> TYPE_attr_values;
//.....
};
//...
C_html4_tags::C_html4_tags() {
//........
map<S_browser, TYPE_attr_values> attr_supported_attr_values_map;
S_browser dummy_browser; //a fake browser key for referencing a fully Html 4.01-compliant supported attr values list
dummy_browser.name = "Dummy";
//.....
TYPE_attr_values& attr_supported_attr_values = attr_supported_attr_values_map[dummy_browser];
//......
**attr_supported_attr_values = attr_supported_attr_values_map[dummy_browser];**
//...
**attr_supported_attr_values.clear();
attr_supported_attr_values_map.clear();**
//......
**attr_supported_attr_values = attr_supported_attr_values_map[dummy_browser];**
//...
**attr_supported_attr_values.clear();
attr_supported_attr_values_map.clear();**
}
I do the bolded lines multiple times with a bunch of different attributes, with very little difference between them, without a problem until reaching this one attribute (a_tabindex_attr), in which the IDE doesn't report anything wrong when running it normally (except "The program has unexpectedly finished." However, when debugging it, it now reports:
Signal received
The inferior stopped because it received a signal from the Operating
System.
Signal name : SIGSEGV Signal meaning : Segmentation fault
And the backtrace points to the attribute I mentioned above, on the line of code which does this:
attr_supported_attr_values.clear();
Now, after adding some debugging cout lines to the code, I learned that what's happening is, for some reason, even after doing:
attr_supported_attr_values.push_back(attr_value);
the vector object which is the returned mapped value of:
attr_supported_attr_values = attr_supported_attr_values_map[dummy_browser];
is not actually being changed when I push_back an S_html_attr_value object to the referenced vector. Now, I don't why that is, since I do pretty much the exact same thing in a bunch of other attributes' code before this one, without any problem, but for some reason now, on this one, it ain't adding the object to attr_supported_attr_values (which is a reference to the returned mapped value of 'dummy_browser'). And I know this for a fact, because I outputted the size of the internal mapped value object of the map (using an iterator for the map), and it was 0 after the call to push_back(). However, what is even more odd is, I ALSO outputted attr_supported_attr_values.size() after the call to push_back(), and that was 1! Now how could that be since they're both supposed to be the same object??
Note:
The full code of what I'm talking about is below (or at least the attribute code, minus the debugging statements...):
//a_tabindex_attr:
attr_desc = "Specifies the position of an <a> element in the\n"
"tabbing order for the current document.\n"
"The tabbing order defines the order in which\n"
"elements will receive focus when navigated by\n"
"the user via the keyboard. The tabbing order\n"
"may include elements nested within other elements.\n"
"Elements that may receive focus based on tabindex\n"
"adhere to the following rules:\n\n"
"1. Those elements that support this attribute and\n"
"assign a positive value to it are navigated first.\n"
"Navigation proceeds from the element with the\n"
"lowest tabindex value to the element with the\n"
"highest value. Values need not be sequential\n"
"nor must they begin with any particular value.\n"
"Elements that have identical tabindex values\n"
"should be navigated in the order they appear\n"
"in the character stream.\n"
"2. Those elements that do not support this\n"
"attribute or support it and assign it a value\n"
"of \"0\" are navigated next. These elements are\n"
"navigated in the order they appear in the\n"
"character stream.\n"
"3. Elements that are disabled do not participate\n"
"in the tabbing order.";
attr_supported_attr_values = attr_supported_attr_values_map[dummy_browser];
attr_value_desc = "A number you specify for the tab index/order.\n"
"It must be a value between 0 and 32767.";
attr_value_content = "<i>number</i>";
attr_value = C_html4_attributes_obj.getAttrValue(attr_value_desc, attr_value_content,
attr_value_supported_browsers,
attr_value_required, attr_value_deprecated,
attr_value_notes, attr_value_tips);
attr_value.is_relative = true;
attr_supported_attr_values.push_back(attr_value);
try {
N_init_class_members::initAttr(C_html4_attributes::attr_tabindex, a_tabindex_attr, attr_desc,
attr_supported_browsers, attr_supported_attr_values_map, attr_required,
attr_deprecated, attr_notes, attr_tips);
}
catch (const char* exc) {
string exc_str = "Error! Call to N_init_class_members::initAttr() from\n"
"constructor of C_html4_tags class. That function\n"
"reported the following exception:\n\n";
exc_str += exc;
throw (exc_str.c_str()); //re-throw exception
}
a_tabindex_attr.is_standard_attr = true;
a_tabindex_attr.is_optional_attr = true;
//cleanup from attribute operations so we can begin working on the next attribute:
C_html4_attributes_obj.clear(); //wipes the slate clean for all the supported attributes' properties except content
attr_desc.clear();
attr_supported_attr_values.clear();
attr_supported_attr_values_map.clear();
attr_value_desc.clear();
attr_value_content.clear();
Upon compiling, I am getting the following error:
C:\UDK\UDK-2010-03\Development\Src\FixIt\Classes\ZInteraction.uc(41) : Error, Unrecognized member 'OpenMenu' in class 'GameUISceneClient'
Line 41 is the following:
GetSceneClient().OpenMenu("ZInterface.ZNLGWindow");
But when I search for OpenMenu, I find that it is indeed defined in GameUISceneClient.uc of the UDK:
Line 1507: exec function OpenMenu( string MenuPath, optional int PlayerIndex=INDEX_NONE )
It looks like I have everything correct. So what's wrong? Why can't it find the OpenMenu function?
From the wiki page on Legacy:Exec Function:
Exec Functions are functions that a player or user can execute by typing its name in the console. Basically, they provide a way to define new console commands in UnrealScript code.
Okay, so OpenMenu has been converted to a console command. Great. But still, how do I execute it in code? The page doesn't say!
More searching revealed this odd documentation page, which contains the answer:
Now then, there is also a function
within class Console called 'bool
ConsoleCommand(coerce string s)'. to
call your exec'd function,
'myFunction' from code, you type:
* bool isFunctionThere; //optional
isFunctionThere = ConsoleCommand("myFunction myArgument");
So, I replaced my line with the following:
GetSceneClient().ConsoleCommand("OpenMenu ZInterface.ZNLGWindow");
Now this causes another error which I covered in my other question+answer a few minutes ago. But that's it!
Not sure if this is your intent, but if you are trying to create a UIScene based on an Archetype that has been created in the UI Editor, you want to do something like this:
UIScene openedScene;
UIScene mySceneArchetype;
mySceneArchetype = UIScene'Package.Scene';
GameSceneClient = class'UIRoot'.static.GetSceneClient();
//Open the Scene
if( GameSceneClient != none && MySceneArchetype != none )
{
GameSceneClient.OpenScene(mySceneArchetype,LocalPlayer(PlayerOwner.Player), openedScene);
}