大约有 46,000 项符合查询结果（耗时：0.0274秒） [XML]
All falsey values in JavaScript
...
Falsey values in JavaScript
false
Zero of Number type: 0 and also -0, 0.0, and hex form 0x0 (thanks RBT)
Zero of BigInt type: 0n and -0n (new in 2020, thanks GetMeARemoteJob)
"", '' and `` - strings of length 0
null
undefined
NaN
document.all (in HTML browsers only)
This is a ...
Apply a function to every row of a matrix or a data frame
... 3 4
[3,] 5 6
R> apply(M, 1, function(x) 2*x[1]+x[2])
[1] 4 10 16
R>
This takes a matrix and applies a (silly) function to each row. You pass extra arguments to the function as fourth, fifth, ... arguments to apply().
...
How can I scale the content of an iframe?
...ra and Safari if you change the CSS to:
<style>
#wrap { width: 600px; height: 390px; padding: 0; overflow: hidden; }
#frame { width: 800px; height: 520px; border: 1px solid black; }
#frame {
-ms-zoom: 0.75;
-moz-transform: scale(0.75);
-moz-transform-origin...
How to debug Lock wait timeout exceeded on MySQL?
...***
Type: InnoDB
Name:
Status:
=====================================
110514 19:44:14 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 4 seconds
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SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 9014315, signal count 780...
Reset C int array to zero : the fastest way?
Assuming that we have a T myarray[100] with T = int, unsigned int, long long int or unsigned long long int, what is the fastest way to reset all its content to zero (not only for initialization but to reset the content several times in my program)? Maybe with memset?
...
How to get line count of a large file cheaply in Python?
...
40 Answers
40
Active
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Why is XOR the default way to combine hashes?
...om (1-bit) inputs, the AND function output probability distribution is 75% 0 and 25% 1. Conversely, OR is 25% 0 and 75% 1.
The XOR function is 50% 0 and 50% 1, therefore it is good for combining uniform probability distributions.
This can be seen by writing out truth tables:
a | b | a AND b
---+...
How to extract the decision rules from scikit-learn decision-tree?
... print "{}return {}".format(indent, tree_.value[node])
recurse(0, 1)
This prints out a valid Python function. Here's an example output for a tree that is trying to return its input, a number between 0 and 10.
def tree(f0):
if f0 <= 6.0:
if f0 <= 1.5:
return [[ 0.]]
...
Is it possible to change only the alpha of a rgba background colour on hover?
... { display: block; position: relative; }
div { position: absolute; bottom: 0; background-color: rgba(var(--rgb), 0.8); }
a:hover div { background-color: rgba(var(--rgb), 1); }
To understand how this works, see How do I apply opacity to a CSS color variable?
If custom properties are not an option,...
How to initialize a two-dimensional array in Python?
... \
for i in range (0, 10): \
new = [] \ can be replaced } this too
for j in range (0, 10): } with a list /
new.append(foo) / comprehension /
twod...