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QUESTION
I have this:
...ANSWER
Answered 2021-Jun-16 at 02:00Add this to the end of your code in the script
QUESTION
I'm trying to decrease the bundle size of my Vue project, which scaffolded by the vue-cli, by using CDN of firebase, Vue, and Vuetify.
So, I've added links of these CDN in public/index.html
as follow:
ANSWER
Answered 2021-Jun-16 at 01:31If you are using vuetify from vue-cli-plugin-vuetify
(vue add vuetify
), treeshaking and auto component import is enabled by default, by using vuetify-loader
.
If you look into the source code of vue-cli-plugin-vuetify
, it only uses vuetify-loader
if it is present in your package.json
. So removing vuetify-loader
from package.json
should disable this behavior.
QUESTION
ANSWER
Answered 2021-Jun-16 at 01:11The problem is that your CSS selectors include parentheses ()
and dollar signs $
. These symbols already have a special meaning. See:
You can escape these characters using a backslash \
.
QUESTION
I was following along with this tutorial on creating a concurrent counter struct for a usize
value: ConcurrentCounter
. As I understand it, this wrapper struct allows us to mutate our usize
value, with more concise syntax, for example:my_counter.increment(1)
vs. my_counter.lock().unwrap().increment(1)
.
Now in this tutorial our value is of type usize
, but what if we wanted to use a f32
, i32
, or u32
value instead?
I thought that I could do this with generic type arguments:
...ANSWER
Answered 2021-Jun-15 at 23:55I haven't come across such a ConcurrentCounter
library, but crates.io is huge, maybe you find something. However, if you are mostly concerned with primitives such as i32
, there is a better alternative call: Atomics, definitely worth checking out.
Nevertheless, your approach of generalizing the ConcurrentCounter
is going in a good direction. In the context of operation overloading, std::ops
is worth a look. Specifically, you need Add
, Sub
, and Mul
, respectively. Also, you need a Copy
bound (alternatively, a Clone
would also do). So you were pretty close:
QUESTION
How do you calculate the model accuracy in RStudio for logistic regression. The dataset is from Kaggle.
...ANSWER
Answered 2021-Jun-15 at 21:39use the package ML metrics
QUESTION
I have been blocked on this problem for several days. I have bootstrap 3.3.7 in the project root folder. I am rendering some buttons in the django template that should open modal windows when clicked. But the modal functionality is not working. I am following the examples shown on this page: https://www.quackit.com/bootstrap/bootstrap_3/tutorial/bootstrap_modal.cfm
Here is the template code:
...ANSWER
Answered 2021-Jun-15 at 21:53 {% load static %}
{% load static %}
// add this.
QUESTION
How do I get the URL of the current tab in the background service worker in MV3?
Here's what I have:
...ANSWER
Answered 2021-Jun-15 at 21:40You function getTab
seems not right, you are currently trying to query on the url. Not on the query options. The following function should work.
QUESTION
My app consists in letting you add lists in which you can keep your notes. Therefore, I have this NotesListActivity where I can add and keep my Lists. I wanted to filter this lists following the https://www.youtube.com/watch?v=CTvzoVtKoJ8 tutorial and then I tried to adapt it to my code like below. Could you please tell me what is the problem here, cause I don't even get an error, I just not get any title of list as result. So, this is what I have in my RecyclerAdapter:
...ANSWER
Answered 2021-Jun-13 at 20:18The problem is that you are using an empty notesListAll
list for filtering results; you need to populate it with the list of notes in the constructor
QUESTION
GNU grep's basic (BRE) and extended (ERE) syntax is documented at https://www.gnu.org/software/grep/manual/html_node/Regular-Expressions.html and PCRE is summarized at man pcresyntax
, but there is no explicit comparison. What are the differences between GNU grep's basic/extended and PCRE (-P
) regular expressions?
ANSWER
Answered 2021-Jun-15 at 20:55My research of the major syntax and functionality differences from http://www.greenend.org.uk/rjk/tech/regexp.html:
.
in GNU grep does not match null bytes and newlines (but does match newlines when used with--null-data
), while Perl, everything except\n
is matched.[...]
in GNU grep defines POSIX bracket expressions, while Perl uses "character" classes. I'm not sure on the details. See http://www.greenend.org.uk/rjk/tech/regexp.html#bracketexpression- "In basic regular expressions the meta-characters
?
,+
,{
,|
,(
, and)
lose their special meaning; instead use the backslashed versions\?
,\+
,\{
,\|
,\(
, and\)
." From https://www.gnu.org/software/grep/manual/html_node/Basic-vs-Extended.html. ERE matches PCRE syntax. - GNU grep
\w
and\W
are the same as[[:alnum:]]
and[^[:alnum]]
, while Perl uses alphanumeric and underscore. - GNU grep has
\<
and\>
for start and end of word.
Perl supports much more additional functionality:
- "nongreedy {}" with syntax
re{...}?
- additional anchors and character types
\A
,\C
,\d
,\D
,\G
,\p
,\P
,\s
,\S
,\X
.\Z
,\z
. (?#comment)
- shy grouping
(?:re)
, shy grouping + modifiers(?modifiers:re)
- lookahead and negative lookahead
(?=re)
and(?!re)
, lookbehind and negative lookbehind(?<=p)
and(?
- Atomic groups
(?>re)
- Conditional expression
(?(cond)re)
- ... and more, see
man pcresyntax
QUESTION
In C++20, we got the capability to sleep on atomic variables, waiting for their value to change.
We do so by using the std::atomic::wait
method.
Unfortunately, while wait
has been standardized, wait_for
and wait_until
are not. Meaning that we cannot sleep on an atomic variable with a timeout.
Sleeping on an atomic variable is anyway implemented behind the scenes with WaitOnAddress on Windows and the futex system call on Linux.
Working around the above problem (no way to sleep on an atomic variable with a timeout), I could pass the memory address of an std::atomic
to WaitOnAddress
on Windows and it will (kinda) work with no UB, as the function gets void*
as a parameter, and it's valid to cast std::atomic
to void*
On Linux, it is unclear whether it's ok to mix std::atomic
with futex
. futex
gets either a uint32_t*
or a int32_t*
(depending which manual you read), and casting std::atomic
to u/int*
is UB. On the other hand, the manual says
The uaddr argument points to the futex word. On all platforms, futexes are four-byte integers that must be aligned on a four- byte boundary. The operation to perform on the futex is specified in the futex_op argument; val is a value whose meaning and purpose depends on futex_op.
Hinting that alignas(4) std::atomic
should work, and it doesn't matter which integer type is it is as long as the type has the size of 4 bytes and the alignment of 4.
Also, I have seen many places where this trick of combining atomics and futexes is implemented, including boost and TBB.
So what is the best way to sleep on an atomic variable with a timeout in a non UB way? Do we have to implement our own atomic class with OS primitives to achieve it correctly?
(Solutions like mixing atomics and condition variables exist, but sub-optimal)
...ANSWER
Answered 2021-Jun-15 at 20:48You shouldn't necessarily have to implement a full custom atomic
API, it should actually be safe to simply pull out a pointer to the underlying data from the atomic
and pass it to the system.
Since std::atomic
does not offer some equivalent of native_handle
like other synchronization primitives offer, you're going to be stuck doing some implementation-specific hacks to try to get it to interface with the native API.
For the most part, it's reasonably safe to assume that first member of these types in implementations will be the same as the T
type -- at least for integral values [1]. This is an assurance that will make it possible to extract out this value.
... and casting
std::atomic
tou/int*
is UB
This isn't actually the case.
std::atomic
is guaranteed by the standard to be Standard-Layout Type. One helpful but often esoteric properties of standard layout types is that it is safe to reinterpret_cast
a T
to a value or reference of the first sub-object (e.g. the first member of the std::atomic
).
As long as we can guarantee that the std::atomic
contains only the u/int
as a member (or at least, as its first member), then it's completely safe to extract out the type in this manner:
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