大约有 45,000 项符合查询结果（耗时：0.0712秒） [XML]
Why does Math.round(0.49999999999999994) return 1?
....1 This is a specification bug, for precisely this one pathological case.2 Java 7 no longer mandates this broken implementation.3
The problem
0.5+0.49999999999999994 is exactly 1 in double precision:
static void print(double d) {
System.out.printf("%016x\n", Double.doubleToLongBits(d));
}
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Why does ~True result in -2?
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240
int(True) is 1.
1 is:
00000001
and ~1 is:
11111110
Which is -2 in Two's complement1
1 ...
Aggregate / summarize multiple variables per group (e.g. sum, mean)
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Where is this year() function from?
You could also use the reshape2 package for this task:
require(reshape2)
df_melt <- melt(df1, id = c("date", "year", "month"))
dcast(df_melt, year + month ~ variable, sum)
# year month x1 x2
1 2000 1 -80.83405 -224.9540159
2 ...
How do you test that a Python function throws an exception?
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724
Use TestCase.assertRaises (or TestCase.failUnlessRaises) from the unittest module, for example:...
Standard deviation of a list
I want to find mean and standard deviation of 1st, 2nd,... digits of several (Z) lists. For example, I have
8 Answers
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New Array from Index Range Swift
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This works for me:
var test = [1, 2, 3]
var n = 2
var test2 = test[0..<n]
Your issue could be with how you're declaring your array to begin with.
EDIT:
To fix your function, you have to cast your Slice to an array:
func aFunction(numbers: Array<Int...
python tuple to dict
For the tuple, t = ((1, 'a'),(2, 'b'))
dict(t) returns {1: 'a', 2: 'b'}
6 Answers
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How to pass a single object[] to a params object[]
...at you mean in this case.
Foo((object)new object[]{ (object)"1", (object)"2" }));
As an array is a subtype of object, this all works out. Bit of an odd solution though, I'll agree.
share
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improv...
Append a dictionary to a dictionary [duplicate]
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525
You can do
orig.update(extra)
or, if you don't want orig to be modified, make a copy first:
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