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kandi X-RAY | C- Summary
kandi X-RAY | C- Summary
#c语言学生管理系统 C语言学生管理系统 开发环境 VS2012 (vs2012 dev测试 vc++6.0都可以运行).
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QUESTION
I was reading this code (source):
...ANSWER
Answered 2021-Jun-16 at 02:16The n2 - n1
in the case of a negative number as a result when converted to bool
will yield true
. So n1
turns out to be less than n2
. That's why it is a bad practice to use int
s in such Boolean context.
Yes, as stated in the documentation:
...comparison function object which returns true if the first argument is less than the second
But the implementation of the comparison here leads to failure. Try this and see for yourself:
QUESTION
I built an app using Django 3.2.3., but when I try to settup my javascript code for the HTML, it doesn't work. I have read this post Django Static Files Development and follow the instructions, but it doesn't resolve my issue.
Also I couldn't find TEMPLATE_CONTEXT_PROCESSORS
, according to this post no TEMPLATE_CONTEXT_PROCESSORS in django, from 1.7 Django and later, TEMPLATE_CONTEXT_PROCESSORS
is the same as TEMPLATE
to config django.core.context_processors.static
but when I paste that code, turns in error saying django.core.context_processors.static
doesn't exist.
I don't have idea why my javascript' script isn't working.
The configurations are the followings
Settings.py
...ANSWER
Answered 2021-Jun-15 at 18:56Run ‘python manage.py collectstatic’ and try again.
The way you handle static wrong, remove the static dirs in your INSTALLED_APPS out of STATIC_DIRS and set a STATIC_ROOT then collectstatic again.
Add the following as django documentation to your urls.py
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
Giving a bit of context. I'm using c++17. I'm using pointer T* data
because this will interop with cuda code. I'm trying write a parallel version (on CPU) of a histogram creator. The sequential version:
ANSWER
Answered 2021-Jun-16 at 00:46The issue you are having has nothing to do with templates. You cannot invoke std::async()
on a member function without binding it to an instance. Wrapping the call in a lambda does the trick.
Here's an example:
QUESTION
I have this code which prints multiple tables
...ANSWER
Answered 2021-Jun-15 at 20:59So, this is a good opportunity to use purrr::map
. You are half way there by applying code to one dataframe.
You can take the code that you have written above and put it into a function.
QUESTION
I have trouble understanding the first line of code inside this implementation of the bsearch function in C. I understand the search algorithm itself and I have played around with this function to get a good grasp of it but I still do not get what
...ANSWER
Answered 2021-Jun-15 at 21:44Within the function you need to find each element in the passed array. However the type of the array is unknown. You only know the size of each element of the array and the starting address of the array that is passed through the parameter base0. of the type const void *
..
To access an element of the array you need to use the pointer arithmetic. But the type void is incomplete type. Its size is unknown/ So you may not use the pointer of the type (const) void *` in expressions with the pointer arithmetic.
Thus this declaration
QUESTION
I have a dataset that was recorded by observation(each observation has its own row of data). I am looking to combine/condense these rows by the plant they were found on - currently a character variable. All other columns are numerical vales.
EX:
This is the raw data |Sci_Name|Honeybee_count|Other_bee_Obsevrved|Stem_count| |---|---|---|---| |Zizia aurea|1|5|10| |Asclepias viridiflora|15|1|3| |Viola unknown|0|0|4| |Zizia aurea|0|2|6| |Zizia aurea|3|6|3| |Asclepias viridiflora|8|2|17|
and I want:
Sci_Name Honeybee_count Other_bee_Obsevrved Stem_count Zizia aurea 4 13 19 Asclepias viridiflora 23 3 20 Viola unknown 0 0 4I am currently pulling this data from a CSV already in table form. I have been attempting to create a new table/data frame with one entry of each plant species, and blanks/0s for each other variable, which I can then use to c-binding the two together. This, however, has been clunky at best and I am having trouble figuring out how to have each row check itself. I am open to any approach, let me know what you think!
Thanks :D
...ANSWER
Answered 2021-Jun-15 at 18:02We can use the formula method in aggregate
from base R
. On the rhs of the ~
, specify the grouping variable and on the lhs, use .
for denoting the rest of the variables. Specify the FUN
as sum
and it will do the column wise sum by group
QUESTION
When a divide-and-conquer recursive function doesn't yield runtimes low enough, which other improvements could be done?
Let's say, for example, this power
function taken from here:
ANSWER
Answered 2021-Jun-15 at 17:36The primary optimization you should use here is common subexpression elimination. Consider your first piece of code:
QUESTION
This morning I created an MSTest project in C#, and for one of the JSON resources, Visual Studio is showing this warning:
...ANSWER
Answered 2021-Feb-02 at 17:38Apparently all you have to do is to close out the file. It seems to only show when the file is opened.
Perhaps a later version of Visual Studio can make this warning behave more consistently with a standard warning in VS. Really it behaves very much like a refactoring / code cleanup suggestion (which commonly has a grey, squiggly line), rather than an actual warning. It's like it's just been mislabeled in development or whatever. However the good thing is that as long as the file is closed, it doesn't pollute the build or the errors window with warning messages.
QUESTION
I have a pair of iterator, and I would like to use ranges::views::filter(some_predicate)
on it (with the pipe operator). AFAIU I should first convert my pair of iterator into a view. I tried to use ranges::subrange(first, last)
to do so, but I’m getting horrible error messages.
Note1: I’m using C++14 and range-v3 version 0.9.1 (the last version compatible with gcc-5.5). If the solution differs when using C++17/20 and/or when using C++20 std::ranges, I’m also interested to know what changed.
Note2: I find the documentation of range-v3 severely lacking, so I’m using cppreference.com. If you know a better documentation, I’m very interested.
EDIT:
In my real code, I’m wrapping a java-style legacy iterator (that has a next()
method instead of operator++
/operator*
. I’m wrapping them in a C++-compatible wrapper. Then I tried to convert that wrapper into a view, and finally filter it. I reproduce a minimal example on godbolt. This use iterator_range
as suggested, but it still doesn’t compile (see the second edit below).
ANSWER
Answered 2021-Apr-08 at 16:24In ranges-v3, there is iterator_range
which you can use to wrap the iterators into a range object.
In C++20, you can use std::span
to wrap those iterators into an range object
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