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What does the `forall` keyword in Haskell/GHC do?
... b)
ghci> liftTup (\x -> [x]) (5, "Hello")
No instance for (Num [Char])
...
ghci> -- huh?
ghci> :t liftTup
liftTup :: (t -> t1) -> (t, t) -> (t1, t1)
"Hmm.. why does GHC infer that the tuple must contain two of the same type? Let's tell it they don't have to be"
-- te...
How to get my IP address programmatically on iOS/macOS?
... @"ipv6"
- (NSString *)getIPAddress:(BOOL)preferIPv4
{
NSArray *searchArray = preferIPv4 ?
@[ /*IOS_VPN @"/" IP_ADDR_IPv4, IOS_VPN @"/" IP_ADDR_IPv6,*/ IOS_WIFI @"/" IP_ADDR_IPv4, IOS_WIFI @"/" IP_ADDR_IPv6, IOS_CELLULAR @"/" IP_ADDR_IPv4, IOS_CELLULAR @"/" IP_ADDR...
Is std::vector so much slower than plain arrays?
... created. What happens if we change Pixel to:
struct Pixel
{
unsigned char r, g, b;
};
Result: about 10% faster. Still slower than an array. Hm.
# ./vector
UseArray completed in 3.239 seconds
UseVector completed in 5.567 seconds
Idea #4 - Use iterator instead of loop index
How about usin...
How to use sed to replace only the first occurrence in a file?
... then only looked for starting on the next line. Therefore, both lines are selected in this case, and the s/foo/bar/ substitution is performed on both of them.
sed '1,/foo/ s//bar/' <<<$'1foo\n2foo\n3foo' fails: with sed: first RE may not be empty (BSD/macOS) and sed: -e expression #1, char...
printf with std::string?
...style string, you can use the c_str() method of std::string to get a const char * that is null-terminated. Using your example:
#include <iostream>
#include <string>
#include <stdio.h>
int main()
{
using namespace std;
string myString = "Press ENTER to quit program!";
...
How can I use mySQL replace() to replace strings in multiple records?
...GREATERTHAN', '>'), 'LESSTHAN', '<')
You can also do this when you select the data (as opposed to when you save it).
So instead of :
SELECT MyURLString From MyTable
You could do
SELECT REPLACE (MyURLString, 'GREATERTHAN', '>') as MyURLString From MyTable
...
invalid multibyte char (US-ASCII) with Rails and Ruby 1.9
...ave you tried adding a magic comment in the script where you use non-ASCII chars? It should go on top of the script.
#!/bin/env ruby
# encoding: utf-8
It worked for me like a charm.
share
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impro...
Use C++ with Cocoa Instead of Objective-C?
...ving it an extension of .mm, or by right-clicking on the file in Xcode and selecting Get Info > General then changing the File Type to sourcecode.cpp.objcpp. The second option is useful if you have a .cpp file where you want to use Objective-C within a Mac-specific #ifdef.
...
How to check if a String contains only ASCII?
The call Character.isLetter(c) returns true if the character is a letter. But is there a way to quickly find if a String only contains the base characters of ASCII?
...
Best practices for circular shift (rotate) operations in C++
...lude <stdint.h> // for uint32_t
#include <limits.h> // for CHAR_BIT
// #define NDEBUG
#include <assert.h>
static inline uint32_t rotl32 (uint32_t n, unsigned int c)
{
const unsigned int mask = (CHAR_BIT*sizeof(n) - 1); // assumes width is a power of 2.
// assert ( (c<...