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How to change the opacity (alpha, transparency) of an element in a canvas element after it has been
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309
I am also looking for an answer to this question, (to clarify, I want to be able to draw an ima...
How to append rows to an R data frame
...sive insight than system.time:
library(microbenchmark)
microbenchmark(f1(1000), f3(1000), f4(1000), times = 5)
# Unit: milliseconds
# expr min lq median uq max neval
# f1(1000) 1024.539618 1029.693877 1045.972666 1055.25931 1112.769176 5
# f3(1000) ...
Return 0 if field is null in MySQL
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Use IFNULL:
IFNULL(expr1, 0)
From the documentation:
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
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How do I get Month and Date of JavaScript in 2 digit format?
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("0" + this.getDate()).slice(-2)
for the date, and similar:
("0" + (this.getMonth() + 1)).slice(-2)
for the month.
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Is std::vector so much slower than plain arrays?
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UseVector completed in 4.412 seconds
UseVectorPushBack completed in 8.017 seconds
The whole thing completed in 14.626 seconds
So array is twice as quick as vector.
But after looking at the code in more detail this is expected; as you run across the vector twice and the array only once. ...
How to convert a string to an integer in JavaScript?
...simplest way would be to use the native Number function:
var x = Number("1000")
If that doesn't work for you, then there are the parseInt, unary plus, parseFloat with floor, and Math.round methods.
parseInt:
var x = parseInt("1000", 10); // you want to use radix 10
// so you get a decimal n...
Generating random numbers in Objective-C
...a head mainly, and I want a way to generate a pseudo-random number between 0 and 74. In Java I would use the method:
13 Ans...
Creating a UIImage from a UIColor to use as a background image for UIButton [duplicate]
... (UIImage *)imageFromColor:(UIColor *)color {
CGRect rect = CGRectMake(0, 0, 1, 1);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [color CGColor]);
CGContextFillRect(context, rect);
UIImag...
Why does HTML5 form-validation allow emails without a dot?
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Ali AlaviAli Alavi
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7
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Convert a character digit to the corresponding integer in C
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As per other replies, this is fine:
char c = '5';
int x = c - '0';
Also, for error checking, you may wish to check isdigit(c) is true first. Note that you cannot completely portably do the same for letters, for example:
char c = 'b';
int x = c - 'a'; // x is now not necessarily 1
Th...