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CHECK constraint in MySQL is not working
... answered Jan 22 '10 at 7:11
David KerinsDavid Kerins
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Numbering rows within groups in a data frame
...l, df$cat, FUN = seq_along)
or:
library(plyr)
ddply(df, .(cat), mutate, id = seq_along(val))
or:
library(dplyr)
df %>% group_by(cat) %>% mutate(id = row_number())
or (the most memory efficient, as it assigns by reference within DT):
library(data.table)
DT <- data.table(df)
DT[, id...
Custom fonts in iOS 7
...our font in .otf or .ttf copied to your project. For example in Supporting Files.
You need to edit .plist file. Add "Fonts provided by application" key into your plist and in Item 0 copy the exact filename of the font you copied to your Supporting files WITH extension. For example: "JosefinSansStd-L...
NULL vs nil in Objective-C
...
nil should only be used in place of an id, what we Java and C++ programmers would think of as a pointer to an object. Use NULL for non-object pointers.
Look at the declaration of that method:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object...
How do you specify that a class property is an integer?
...rimenting with TypeScript, and in the process of creating a class with an "ID" field that should be an integer, I have gotten a little confused.
...
Importing CommonCrypto in a Swift framework
...ete the umbrella header, CommonCrypto.h.)
Add a new Configuration Settings File and name it, e.g., "CommonCrypto.xcconfig". (Don't check any of your targets for inclusion.) Populate it with the following:
MODULEMAP_FILE[sdk=iphoneos*] = \
$(SRCROOT)/CommonCrypto/iphoneos.modulemap
MODULE...
How to make/get a multi size .ico file? [closed]
I simply want to have an .ico file that has multiple sizes of the icon image contained within it. I'd like it for use in a cross-platform desktop application (so that, e.g. on Windows, the 16x16 size is used for the app's top bar but a 32x32 size version is used when the various open apps are shown...
How do I rename all folders and files to lowercase on Linux?
.../\L$2/' {} \;
This avoids problems with directories being renamed before files and trying to move files into non-existing directories (e.g. "A/A" into "a/a").
Or, a more verbose version without using "rename".
for SRC in `find my_root_dir -depth`
do
DST=`dirname "${SRC}"`/`basename "${SRC}" ...
.a: error adding symbols: File format not recognized 原因 - 操作系统(...
.a: error adding symbols: File format not recognized 原因error-adding-symbols-file-format-not-recognizedlinux,gccLinux编译链接时报错：xxx a: error adding symbols: File format not recognized。也可能出现编译能通过，但ldd报链接失败不能运行。原因是：在低版本Linux...
解决：apache2.service: Failed to run \'start\' task: No such file or d...
解决：apache2.service: Failed to run 'start' task: No such file or directoryapache2-service-failed-to-run-start-task-no-such-file-or-directory今天重启apache2时，出现一个错误：apache2 service: Failed to run & 39;start& 39; task: No such file or directory。原因是：& 39; var tmp& 3...