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【转】用App Inventor 2实现电子围栏功能 - App应用开发 - 清泛IT社区，为创新赋能！
在行空板《家庭安全相册》项目中，第四部分是手机APP监护人部分。这部分需要完成手机获取家庭成员传送回来的位置后，计算是否在安全的电子围栏范围内。因为电子围栏是相对复杂的部分，因此独立一章详细说明。
App In...
What is the equivalent of “!=” in Excel VBA?
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Fun fact to back this answer: Visual Basic and Pascal languages store strings with their length in the beginning and the content itself right after that. C-based and Java languages, on the other hand, do not store the length and have the '\0' (null) terminator to sign...
Does delete on a pointer to a subclass call the base class destructor?
...s a heap memory allocation for one of its fields. Class A is instantiated and stored as a pointer field in another class ( class B .
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What is the difference between “ is None ” and “ ==None ”
...o quote:
A class is free to implement
comparison any way it chooses, and it
can choose to make comparison against
None mean something (which actually
makes sense; if someone told you to
implement the None object from
scratch, how else would you get it to
compare True against itself...
How to generate a core dump in Linux on a segmentation fault?
...s on what shell you are using. If you are using bash, then the ulimit command controls several settings relating to program execution, such as whether you should dump core. If you type
ulimit -c unlimited
then that will tell bash that its programs can dump cores of any size. You can specify a ...
How to split a String by space
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I find it useful as my use case was to split the string and remove multiple spaces. One line of code does both for me.
– Niharika Upadhyay
Jul 10 '18 at 9:06
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Is there a command like “watch” or “inotifywait” on the Mac?
I want to watch a folder on my Mac (Snow Leopard) and then execute a script (giving it the filename of what was just moved into a folder (as a parameter... x.sh "filename")).
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Pointer arithmetic for void pointer in C
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Final conclusion: arithmetic on a void* is illegal in both C and C++.
GCC allows it as an extension, see Arithmetic on void- and Function-Pointers (note that this section is part of the "C Extensions" chapter of the manual). Clang and ICC likely allow void* arithmetic for the purpose...
How do I use Linq to obtain a unique list of properties from a list of objects?
...operty. I'd like to be able to do this without looping through each object and pulling out the unique ids that I find.
5 An...
Library not loaded: libmysqlclient.16.dylib error when trying to run 'rails server' on OS X 10.6 wit
...never able to get any of these answers to work for me, but this is the command that I used to make it work for me. This way you don't need to use install_name_tool every time you update your mysql
sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib
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