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How to remove a key from Hash and get the remaining hash in Ruby/Rails?
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14 Answers
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What is the Ruby (spaceship) operator?
...roovy is another language that supports it. Basically instead of returning 1 (true) or 0 (false) depending on whether the arguments are equal or unequal, the spaceship operator will return 1, 0, or −1 depending on the value of the left argument relative to the right argument.
a <=> b :=
i...
All combinations of a list of lists
... need itertools.product:
>>> import itertools
>>> a = [[1,2,3],[4,5,6],[7,8,9,10]]
>>> list(itertools.product(*a))
[(1, 4, 7), (1, 4, 8), (1, 4, 9), (1, 4, 10), (1, 5, 7), (1, 5, 8), (1, 5, 9), (1, 5, 10), (1, 6, 7), (1, 6, 8), (1, 6, 9), (1, 6, 10), (2, 4, 7), (2, 4, 8),...
Programmatically obtain the Android API level of a device?
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107
You can obtain API level programatically by the system constant (Build.VERSION.SDK_INT). For e...
Format number to always show 2 decimal places
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1197
(Math.round(num * 100) / 100).toFixed(2);
Live Demo
var num1 = "1";
document.getEleme...
What is Weak Head Normal Form?
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These expressions are all in normal form:
42
(2, "hello")
\x -> (x + 1)
These expressions are not in normal form:
1 + 2 -- we could evaluate this to 3
(\x -> x + 1) 2 -- we could apply the function
"he" ++ "llo" -- we could apply the (++)
(1 + 1, 2 + 2) ...
Fastest way to iterate over all the chars in a String
...e now Java will store strings as byte[] by default.
SECOND UPDATE: As of 2016-10-25, on my AMDx64 8core and source 1.8, there is no difference between using 'charAt' and field access. It appears that the jvm is sufficiently optimized to inline and streamline any 'string.charAt(n)' calls.
THIRD UPDAT...
What is the best regular expression to check if a string is a valid URL?
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Replacing NAs with latest non-NA value
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18 Answers
18
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“Cloning” row or column vectors
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Here's an elegant, Pythonic way to do it:
>>> array([[1,2,3],]*3)
array([[1, 2, 3],
[1, 2, 3],
[1, 2, 3]])
>>> array([[1,2,3],]*3).transpose()
array([[1, 1, 1],
[2, 2, 2],
[3, 3, 3]])
the problem with [16] seems to be that the transpose ha...