semantics | Этот репозиторий содержит материалы , необходимые для
kandi X-RAY | semantics Summary
kandi X-RAY | semantics Summary
Этот репозиторий содержит материалы, необходимые для воспроизведения премеров из статьи "Введение в словарный и семантический анализ документов (на примере предвыборных программ кандидатов в президенты Беларуси)", опубликованной в блоге "R: Анализ и визуализация данных". В частности, здесь можно найти:.
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Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of semantics
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Trending Discussions on semantics
QUESTION
I wish to suggest (perhaps enforce, but I am not firm on the semantics yet) a particular format for the output of a PowerShell function.
about_Format.ps1xml (versioned for PowerShell 7.1) says this: 'Beginning in PowerShell 6, the default views are defined in PowerShell source code. The Format.ps1xml files from PowerShell 5.1 and earlier versions don't exist in PowerShell 6 and later versions.'. The article then goes on to explain how Format.ps1xml files can be used to change the display of objects, etc etc. This is not very explicit: 'don't exist' -ne 'cannot exist'...
This begs several questions:
- Although they 'don't exist', can Format.ps1xml files be created/used in versions of PowerShell greater than 5.1?
- Whether they can or not, is there some better practice for suggesting to PowerShell how a certain function should format returned data? Note that inherent in 'suggest' is that the pipeline nature of PowerShell's output must be preserved: the user must still be able to pipe the output of the function to Format-List or ForEach-Object etc..
For example, the Get-ADUser
cmdlet returns objects formatted by Format-List
. If I write a function called Search-ADUser
that calls Get-ADUser
internally and returns some of those objects, the output will also be formatted as a list. Piping the output to Format-Table
before returning it does not satisfy my requirements, because the output will then not be treated as separate objects in a pipeline.
Example code:
...ANSWER
Answered 2021-Jun-15 at 18:36Although they 'don't exist', can
Format.ps1xml
files be created/used in versions of PowerShell greater than 5.1?
Yes; in fact any third-party code must use them to define custom formatting.
- That
*.ps1xml
files are invariably needed for such definitions is unfortunate; GitHub issue #7845 asks for an in-memory, API-based alternative (which for type data already exists, via theUpdate-TypeData
cmdlet).
- That
It is only the formatting data that ships with PowerShell that is now hardcoded into the PowerShell (Core) executable, presumably for performance reasons.
is there some better practice for suggesting to PowerShell how a certain function should format returned data?
The lack of an API-based way to define formatting data requires the following approach:
Determine the full name of the .NET type(s) to which the formatting should apply.
If it is
[pscustomobject]
instances that the formatting should apply to, you need to (a) choose a unique (virtual) type name and (b) assign it to the[pscustomobject]
instances via PowerShell's ETS (Extended Type System); e.g.:For
[pscustomobject]
instances created by theSelect-Object
cmdlet:
QUESTION
This could be just semantics and may be a stupid question, but I'm curious if the following would be considered overloading:
...ANSWER
Answered 2021-Jun-15 at 18:38When in doubt, JLS will help:
If two methods of a class (whether both declared in the same class, or both inherited by a class, or one declared and one inherited) have the same name but signatures that are not override-equivalent, then the method name is said to be overloaded.
So it's not "changing the parameters", it is about not override-equivalent. To find out what that is, you go to another chapter, that says:
Two method signatures m1 and m2 are override-equivalent iff either m1 is a subsignature of m2 or m2 is a subsignature of m1.
And the same chapter explains what subsignature is:
The signature of a method m1 is a subsignature of the signature of a method m2 if either:
m2 has the same signature as m1, or
the signature of m1 is the same as the erasure (§4.6) of the signature of m2.
How you interpret your above methods is an exercise left to you.
QUESTION
I am querying a database for an item using R2DBC and Spring Integration. I want to extend the transaction boundary a bit to include a handler - if the handler fails I want to roll back the database operation. But I'm having difficulty even establishing transactionality explicitly in my integration flow. The flow is defined as
...ANSWER
Answered 2021-Jun-15 at 18:32Well, it's indeed not possible that declarative way since we don't have hook for injecting to the reactive type in the middle on that level.
Try to look into a TransactionalOperator
and its usage from the Java DSL's fluxTransform()
:
QUESTION
It is known that asm volatile ("" ::: "memory")
can serve as a compiler barrier to prevent compiler from reordering assembly instructions across it. For example, it is mentioned in https://preshing.com/20120625/memory-ordering-at-compile-time/, section "Explicit Compiler Barriers".
However, all the articles I can find only mention the fact that asm volatile ("" ::: "memory")
can serve as a compiler barrier without giving a reason why the "memory"
clobber can effectively form a compiler barrier. The GCC online documentation only says that all the special clobber "memory"
does is tell the compiler that the assembly code may potentially perform memory reads or writes other than those specified in operands lists. But how does such a semantic cause compiler to stop any attempt to reorder memory instructions across it? I tried to answer myself but failed, so I ask here: why can asm volatile ("" ::: "memory")
serve as a compiler barrier, based on the semantics of "memory"
clobber? Please note that I am asking about "compiler barrier" (in effect at compile-time), not stronger "memory barrier" (in effect at run-time). For convenience, I excerpt the semantics of "memory"
clobber in GCC online doc below:
...The
"memory"
clobber tells the compiler that the assembly code performs memory reads or writes to items other than those listed in the input and output operands (for example, accessing the memory pointed to by one of the input parameters). To ensure memory contains correct values, GCC may need to flush specific register values to memory before executing theasm
. Further, the compiler does not assume that any values read from memory before anasm
remain unchanged after thatasm
; it reloads them as needed. Using the"memory"
clobber effectively forms a read/write memory barrier for the compiler.
ANSWER
Answered 2021-Jun-11 at 23:37If a variable is potentially read or written, it matters what order that happens in. The point of a "memory"
clobber is to make sure the reads and/or writes in an asm
statement happen at the right point in the program's execution.
Any read of a C variable's value that happens in the source after an asm
statement must be after the memory-clobbering asm
statement in the compiler-generated assembly output for the target machine, otherwise it might be reading a value before the asm statement would have changed it.
Any read of a C var in the source before an asm
statement similarly must stay sequenced before, otherwise it might incorrectly read a modified value.
Similar reasoning applies to assignments to (writes of) C variables before/after any asm
statement with a "memory"
clobber. Just like a function call to an "opaque" function, one who's definition the compiler can't see.
No reads or writes can reorder with the barrier in either direction, therefore no operation before the barrier can reorder with any operation after the barrier, or vice versa.
Another way to look at it: the actual machine memory contents must match the C abstract machine at that point. The compiler-generated asm has to respect that, by storing any variable values from registers to memory before the start of an asm("":::"memory")
statement, and afterwards it has to assume that any registers that had copies of variable values might not be up to date anymore. So they have to be reloaded if they're needed.
This reads-everything / writes-everything assumption for the "memory"
clobber is what keeps the asm
statement from reordering at all at compile time wrt. all accesses, even non-volatile
ones. The volatile
is already implicit from being an asm()
statement with no "=..."
output operands, and is what stops it from being optimized away entirely (and with it the memory clobber).
Note that only potentially "reachable" C variables are affected. For example, escape analysis can still let the compiler keep a local int i
in a register across a "memory"
clobber, as long as the asm statement itself doesn't have the address as an input.
Just like a function call: for (int i=0;i<10;i++) {foobar("%d\n", i);}
can keep the loop counter in a register, and just copy it to the 2nd arg-passing register for foobar every iteration. There's no way foobar can have a reference to i
because its address hasn't been stored anywhere or passed anywhere.
(This is fine for the memory barrier use-case; no other thread could have its address either.)
Related:
- How does a mutex lock and unlock functions prevents CPU reordering? - why opaque function calls work as compiler barriers.
- How can I indicate that the memory *pointed* to by an inline ASM argument may be used? - cases where a
"memory"
clobber is needed for a non-emptyasm
statement (or other dummy operands to tell the asm statement which memory is read / written.)
QUESTION
I am attempting to use the WPGraphQL plugin for WordPress with PeachPie. I've built it out using a Visual Studio 2019 solution with two projects based on the ASP.NET Core Empty template with the Target Framework set to .NET 5.0.
I have successfully set up an initial project that utilizes the default Nuget package, PeachPied.WordPress.AspNetCore. It runs correctly, and renders the WordPress page as expected. The project file for this first one looks like this:
...ANSWER
Answered 2021-Jun-11 at 18:27It's a big in peachpie compiler itself.
https://github.com/peachpiecompiler/peachpie/issues/957
You van either delete the failing code from the php script or wait for the next release of peachpie.
QUESTION
I need to define a method that serializes objects for storage, but the semantics of it require that it can only work with objects whose fields keys are of string type (because they must match the column's names, so they cannot be numbers).
Using a Record
type won't work for this serializer input, because I am supplying it objects that have specific fields defined (like interface Foo {foo: number, bar: string}
and these are not assignable to Record
).
Same thing why we cannot do safely assign a List
to a List
if List
is mutable, but we can if they are immutable .
So I need to either specify that a generic type parameter's keyof T
is a subset of string
or have a ReadOnlyRecord
that is covariant with any interface that has string keys.
Suggestions?
...ANSWER
Answered 2021-Jun-11 at 13:25You do not need to take variance into account here. The reason why Record
fails is simply due to the utility requiring its type parameter to have an index signature. For the same reason, the method cannot expect to get a type assignable to { [x:string]: unknown }
as its only parameter.
In any case, I do not think you will be able to do that without generic type parameters. Then you simply need to check if a string-only keyed type like { [P in Extract : any }
is assignable to the passed-in type (the other way around will obviously always pass as your interfaces are subtypes of the former).
Note that X extends T ? T : never
in the parameter is needed for the compiler to be able to infer T
from usage while still maintaining the constraint. The only caveat is that you will not be able to catch symbol
properties (but will be if their type is unique symbol
):
QUESTION
I have a templated class used for modelling views on objects, like std::shared_ptr
and std::weak_ptr
but without any owning semantics. The class internally holds a pointer to the viewed object and a functor which is called on class destruction (It is useful for reference counting the viewed object, or for thread-safe locking and releasing of the viewed resource).
Like the standard library counterparts, I would like my class to behave as expected when the owned object is an array (T[]
). The problem I am facing comes from the fact that a pointer to an array of unknown bound is, by my understanding, illegal C++. More specifically, given that the template parameter of the class T
is, say, int[]
, when in my class I write:
ANSWER
Answered 2021-Jun-10 at 22:48The problem I am facing comes from the fact that a pointer to an array of unknown bound is, by my understanding, illegal C++.
You're mistaken. Pointer to an array of unknown bound is not illegal in C++.
I am in fact invoking undefined behaviour. (Or, possibly, some non-standard compiler extension?)
Neither (as long as the pointer is valid). The shown function is standard conforming even if T
is an array of unknown bound.
why are pointers and references to arrays of unknown bound illegal?
They aren't illegal.
There used to be a special case that pointers and references to arrays of unknown bound were illegal as function parameters. That was made legal in a defect resolution in 2014
QUESTION
Other than the usual suspects (process.exit()
, or process termination/signal, or crash/hardware failure), are there any circumstances where code in a finally block will not be reached?
The following typescript code usually executes as expected (using node.js) but occasionally will terminate immediately at line 4 with no exceptions being raised or change in the process exit code (exits 0/success):
...ANSWER
Answered 2021-Mar-12 at 02:03Other than the usual suspects (process.exit(), or process termination/signal, or crash/hardware failure), are there any circumstances where code in a finally block will not be reached?
If the promise will resolve or reject in future then it should reach to the final block.
According to the MDN docs,
The
finally
-block contains statements to execute after thetry
-block andcatch
-block(s) execute, but before the statements following thetry...catch...finally
-block. Note that thefinally
-block executes regardless of whether an exception is thrown. Also, if an exception is thrown, the statements in thefinally
-block execute even if nocatch
-block handles the exception.
A promise is just a JavaScript object. An object can have many states. A promise object can be in pending
state or settled
state. The state settled
can divide as fulfilled
and rejected
. For this example just imagine we have only two state as PENDING
and SETTLED
.
Now if the promise never resolve or reject then it will never go to the settled
state which means your then..catch..finally
will never call. If nothing is reference to the promise then it will just garbage collected.
In your original question you mentioned about a 3rd party async method. If you see that code, the first thing you can see is, there are set of if(..)
blocks to determine the current OS.
But it does not have any else
block or a default case.
What if non of the if(..)
blocks are trigger ? There is nothing to execute and you already returned a promise with return new Promise()
. So basically if non of the if(..)
blocks are triggered, the promise will never change its state from pending
to settled
.
And then as @Bergi also mentioned there are some codes like this. A classic Promise constructor antipattern as he mentioned. For example see the below code,
QUESTION
JavaScript's event loop uses a message queue to schedule work, and runs each message to completion before starting the next. As a result, a niche-but-surprisingly-common pattern in JavaScript code is to schedule a function to run after the messages currently in the queue have been processed using setTimeout(fn, 0)
. For example:
ANSWER
Answered 2021-May-25 at 03:09Raku doesn't have an ordered message queue. It has an unordered list of things that needs doing.
QUESTION
The following code compiles under Clang/GCC under the C++17 standard, but does not compile under MSVC with -std:C++17 /Zc:ternary
.
ANSWER
Answered 2021-Jun-05 at 01:52This is Core issue 1805, which changed ?:
to decay arrays and functions to pointers before testing whether the other operand can be converted to it. The example in that issue is basically the one in your question:
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