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How to concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
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Standard C Preprocessor
$ cat xx.c
#define VARIABLE 3
#define PASTER(x,y) x ## _ ## y
#define EVALUATOR(x,y) PASTER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)
extern void NAME(mine)(char *x);
$ gcc -E xx.c
# 1 "xx.c"
# ...
Difference between “and” and && in Ruby?
What is the difference between the && and and operators in Ruby?
7 Answers
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What are C++ functors and their uses?
...about functors in C++. Can someone give me an overview as to what they are and in what cases they would be useful?
14 Answe...
Cartesian product of x and y array points into single array of 2D points
I have two numpy arrays that define the x and y axes of a grid. For example:
13 Answers
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Switch statement: must default be the last case?
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The C99 standard is not explicit about this, but taking all facts together, it is perfectly valid.
A case and default label are equivalent to a goto label. See 6.8.1 Labeled statements. Especially interesting is 6.8.1.4, which enables...
How to delete duplicate lines in a file without sorting it in Unix?
...ay then seen[$0] will evaluate to false. The ! is the logical NOT operator and will invert the false to true. Awk will print the lines where the expression evaluates to true. The ++ increments seen so that seen[$0] == 1 after the first time a line is found and then seen[$0] == 2, and so on.
Awk eval...
Understanding dict.copy() - shallow or deep?
... 3, 4, 5]}, {1: [1, 2, 3, 4]})
So:
b = a: Reference assignment, Make a and b points to the same object.
b = a.copy(): Shallow copying, a and b will become two isolated objects, but their contents still share the same reference
b = copy.deepcopy(a): Deep copying, a and b's structure and conte...
What is the rationale for fread/fwrite taking size and count as arguments?
We had a discussion here at work regarding why fread and fwrite take a size per member and count and return the number of members read/written rather than just taking a buffer and size. The only use for it we could come up with is if you want to read/write an array of structs which aren't evenly div...
Hidden features of Python [closed]
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In case you're thinking it's doing 1 < x, which comes out as True, and then comparing True < 10, which is also True, then no, that's really not what happens (see the last example.) It's really translating into 1 < x and x < 10, and x < 10 and 10 < x * 10 and x*10 < 100, but...
Confusion between factor levels and factor labels
There seems to be a difference between levels and labels of a factor in R.
Up to now, I always thought that levels were the 'real' name of factor levels, and labels were the names used for output (such as tables and plots). Obviously, this is not the case, as the following example shows:
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