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How do I calculate the normal vector of a line segment?
Suppose I have a line segment going from (x1,y1) to (x2,y2). How do I calculate the normal vector perpendicular to the line?
...
How can I change the color of pagination dots of UIPageControl?
... Core Graphics to render the dots in the colors you specify.
You use the exposed properties to customize and control it.
If you want to you can register a delegate object to get notifications when the user taps on one of the little page dots. If no delegate is registered then the view will not rea...
Draw in Canvas by finger, Android
...aint demo in the sdk sample.
Another Sample:
public class MainActivity extends Activity {
DrawingView dv ;
private Paint mPaint;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
dv = new DrawingView(this);
...
Python - Create list with numbers between 2 values?
How would I create a list with values between two values I put in?
For example, the following list is generated for values from 11 to 16:
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What is the syntax rule for having trailing commas in tuple definitions?
...
In all cases except the empty tuple the comma is the important thing. Parentheses are only required when required for other syntactic reasons: to distinguish a tuple from a set of function arguments, operator precedence, or to allow line b...
How to skip over an element in .map()?
... has some cost, you can use the more general .reduce(). You can generally express .map() in terms of .reduce:
someArray.map(function(element) {
return transform(element);
});
can be written as
someArray.reduce(function(result, element) {
result.push(transform(element));
return result;
}, []);...
How to catch integer(0)?
... length integers, then you want something like
is.integer0 <- function(x)
{
is.integer(x) && length(x) == 0L
}
Check it with:
is.integer0(integer(0)) #TRUE
is.integer0(0L) #FALSE
is.integer0(numeric(0)) #FALSE
You can also use assertive for this.
library(assertive)
x &l...
How do you calculate log base 2 in Java for integers?
...oid FP calculations whenever possible.
Floating-point operations are not exact. You can never know for sure what will (int)(Math.log(65536)/Math.log(2)) evaluate to. For example, Math.ceil(Math.log(1<<29) / Math.log(2)) is 30 on my PC where mathematically it should be exactly 29. I didn't fi...
Way to go from recursion to iteration
... on the outside, you just pop an action/continuation off the stack, apply/execute it, push the actions it returned on the stack in reverse in order and repeat. Contingent/complex traversals, you just capture what would have been local stack variables in reference-counted pointers that you close ov...
Java 8: Lambda-Streams, Filter by Method with Exception
I have a problem trying out the Lambda expressions of Java 8.
Usually it works fine, but now I have methods that throw IOException 's.
It's best if you look at the following code:
...