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Why use double indirection? or Why use pointers to pointers?
When should a double indirection be used in C? Can anyone explain with a example?
18 Answers
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Reading from text file until EOF repeats last line [duplicate]
...he following C++ code uses a ifstream object to read integers from a text file (which has one number per line) until it hits EOF . Why does it read the integer on the last line twice? How to fix this?
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“for loop” with two variables? [duplicate]
...ested for loop, use:
import itertools
for i, j in itertools.product(range(x), range(y)):
# Stuff...
If you just want to loop simultaneously, use:
for i, j in zip(range(x), range(y)):
# Stuff...
Note that if x and y are not the same length, zip will truncate to the shortest list. As @a...
variable === undefined vs. typeof variable === “undefined”
...for comparison can throw an error whereas a typeof check never will.
For example, the following is used in IE for parsing XML:
var x = new ActiveXObject("Microsoft.XMLDOM");
To check whether it has a loadXML method safely:
typeof x.loadXML === "undefined"; // Returns false
On the other hand:
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Static variable inside of a function in C
...ope.
The scope of variable is where the variable name can be seen. Here, x is visible only inside function foo().
The lifetime of a variable is the period over which it exists. If x were defined without the keyword static, the lifetime would be from the entry into foo() to the return from foo();...
Immutable vs Mutable types
... know the float object is considered to be immutable, with this type of example from my book:
16 Answers
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Efficient evaluation of a function at every cell of a NumPy array
...irectly to a Numpy array each time you need it:
import numpy as np
def f(x):
return x * x + 3 * x - 2 if x > 0 else x * 5 + 8
f = np.vectorize(f) # or use a different name if you want to keep the original f
result_array = f(A) # if A is your Numpy array
It's probably better to specify...
Test for equality among all elements of a single vector
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I use this method, which compares the min and the max, after dividing by the mean:
# Determine if range of vector is FP 0.
zero_range <- function(x, tol = .Machine$double.eps ^ 0.5) {
if (length(x) == 1) return(TRUE)
x <- range(x) / mean(x)
isTRUE(all.equal(x[1], ...
Does a favicon have to be 32x32 or 16x16?
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Update for 2020: Sticking to the original question of 16x16 versus 32x32 icons: the current recommendation should be to provide a 32x32 icon, skipping 16x16 entirely. All current browsers and devices support 32x32 icons. The icon will routinely be upscaled to as much as 192x192 de...
How to add a border just on the top side of a UIView
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