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What tools are there for functional programming in C?
...
FFCALL lets you build closures in C -- callback = alloc_callback(&function, data) returns a function pointer such that callback(arg1, ...) is equivalent to calling function(data, arg1, ...). You will have to handle garbage collection manually, though.
Relatedly, blocks have...
Extracting text OpenCV
...s(cv::Mat img)
{
std::vector<cv::Rect> boundRect;
cv::Mat img_gray, img_sobel, img_threshold, element;
cvtColor(img, img_gray, CV_BGR2GRAY);
cv::Sobel(img_gray, img_sobel, CV_8U, 1, 0, 3, 1, 0, cv::BORDER_DEFAULT);
cv::threshold(img_sobel, img_threshold, 0, 255, CV_THRESH_O...
How can I get the MAC and the IP address of a connected client in PHP?
...
Server IP
You can get the server IP address from $_SERVER['SERVER_ADDR'].
Server MAC address
For the MAC address, you could parse the output of netstat -ie in Linux, or ipconfig /all in Windows.
Client IP address
You can get the client IP from $_SERVER['REMOTE_ADDR']
C...
Add Foreign Key to existing table
...
To add a foreign key (grade_id) to an existing table (users), follow the following steps:
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0;
ALTER TABLE users ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
...
Property getters and setters
...g to backup the computed property. Try this:
class Point {
private var _x: Int = 0 // _x -> backingX
var x: Int {
set { _x = 2 * newValue }
get { return _x / 2 }
}
}
Specifically, in the Swift REPL:
15> var pt = Point()
pt: Point = {
_x = 0
}
16> pt.x = 10...
How can I quantify difference between two images?
...ead images as 2D arrays (convert to grayscale for simplicity)
img1 = to_grayscale(imread(file1).astype(float))
img2 = to_grayscale(imread(file2).astype(float))
# compare
n_m, n_0 = compare_images(img1, img2)
print "Manhattan norm:", n_m, "/ per pixel:", n_m/img1.size
print "Z...
How to initialize an array in one step using Ruby?
...rray = [ '1', '2', '3' ]
You can also use a range:
array = ('1'..'3').to_a # parentheses are required
# or
array = *('1'..'3') # parentheses not required, but included for clarity
For arrays of whitespace-delimited strings, you can use Percent String syntax:
array = %w[ 1 2 3 ]
You can...
Is it possible to use argsort in descending order?
... this method is that ids is a view of avgDists:
>>> ids.flags
C_CONTIGUOUS : False
F_CONTIGUOUS : False
OWNDATA : False
WRITEABLE : True
ALIGNED : True
UPDATEIFCOPY : False
(The 'OWNDATA' being False indicates this is a view, not a copy)
Another way to do this is something ...
How do I clone a Django model instance object and save it to the database?
...imary key of your object and run save().
obj = Foo.objects.get(pk=<some_existing_pk>)
obj.pk = None
obj.save()
If you want auto-generated key, set the new key to None.
More on UPDATE/INSERT here.
Official docs on copying model instances: https://docs.djangoproject.com/en/2.2/topics/db/que...
How to concatenate two MP4 files using FFmpeg?
...puts).
ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv \
-filter_complex "[0:v] [0:a] [1:v] [1:a] [2:v] [2:a]
concat=n=3:v=1:a=1 [v] [a]" \
-map "[v]" -map "[a]" output.mkv
Note that this method performs a re-encode.
2. concat demuxer
Use this method wh...