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What is a higher kinded type in Scala?
...pply to value arguments to "construct" a value.
Value constructors are usually called "functions" or "methods". These "constructors" are also said to be "polymorphic" (because they can be used to construct "stuff" of varying "shape"), or "abstractions" (since they abstract over what varies between ...
Number of elements in a javascript object
...
Although JS implementations might keep track of such a value internally, there's no standard way to get it.
In the past, Mozilla's Javascript variant exposed the non-standard __count__, but it has been removed with version 1.8.5.
For cross-browser scripting you're stuck with explicitly ite...
How can I have a newline in a string in sh?
...rom the Bash manual page:
Words of the form $'string' are treated specially. The word expands to
string, with backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash escape sequences, if present, are decoded
as follows:
\a alert (bell)
...
Convert a row of a data frame to vector
...
Might have been changed in the meantime, but today unlist allows dropping names: identical(unlist(df[1,], use.names = FALSE), as.numeric(df[1,])) (and btw df still is not a sensible name for a data.frame... ;-))
– Andri Signorell
Sep 25 '1...
Python: most idiomatic way to convert None to empty string?
...
If you actually want your function to behave like the str() built-in, but return an empty string when the argument is None, do this:
def xstr(s):
if s is None:
return ''
return str(s)
...
C Macro definition to determine big endian or little endian machine?
...
Code supporting arbitrary byte orders, ready to be put into a file called order32.h:
#ifndef ORDER32_H
#define ORDER32_H
#include <limits.h>
#include <stdint.h>
#if CHAR_BIT != 8
#error "unsupported char size"
#endif
enum
{
O32_LITTLE_ENDIAN = 0x03020100ul,
O32_BIG_END...
General guidelines to avoid memory leaks in C++ [closed]
... programs? How do I figure out who should free memory that has been dynamically allocated?
29 Answers
...
Adding information to an exception?
...essage + ' happens at %s' % arg1)
bar('arg1')
Traceback (most recent call last):
File "test.py", line 13, in <module>
bar('arg1')
File "test.py", line 11, in bar
raise type(e)(e.message + ' happens at %s' % arg1)
IOError: Stuff happens at arg1
Update 1
Here's a slight modif...
How do I find out which keystore was used to sign an app?
...ture algorithm name: SHA1withRSA
Then use the keytool again to print out all the aliases of your signing keystore:
keytool -list -keystore my-signing-key.keystore
You will get a list of aliases and their certificate fingerprint:
android_key, Jan 23, 2010, PrivateKeyEntry,
Certificate fingerpri...
Are duplicate keys allowed in the definition of binary search trees?
...cluded. For example, the example algorithms in the MIT Algorithms book usually present examples without duplicates. It is fairly trivial to implement duplicates (either as a list at the node, or in one particular direction.)
Most (that I've seen) specify left children as <= and right children ...