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What exactly is a reentrant function?
...
1. How is safely defined?
Semantically. In this case, this is not a hard-defined term. It just mean "You can do that, without risk".
2. If a program can be safely executed concurrently, does it always mean that it is reentrant?
No.
For example, let's have ...
Storing SHA1 hash values in MySQL
...INARY(20) and CHAR(40).
CREATE TABLE `binary` (
`id` int unsigned auto_increment primary key,
`password` binary(20) not null
);
CREATE TABLE `char` (
`id` int unsigned auto_increment primary key,
`password` char(40) not null
);
With million of records binary(20) takes 44.56M, whil...
O(nlogn) Algorithm - Find three evenly spaced ones within binary string
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Finally! Following up leads in sdcvvc's answer, we have it: the O(n log n) algorithm for the problem! It is simple too, after you understand it. Those who guessed FFT were right.
The problem: we are given a binary string S of l...
Git push/clone to new server
...s something I can't work out. After creating and using a git repository locally on my Mac, can I push a copy to another server somewhere else? I am behind a firewall so unfortunately I can't run git clone from the other machine.
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Java how to replace 2 or more spaces with single space in string and delete leading and trailing spa
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Try this:
String after = before.trim().replaceAll(" +", " ");
See also
String.trim()
Returns a copy of the string, with leading and trailing whitespace omitted.
regular-expressions.info/Repetition
No trim() regex
It's also possible to do this with just one re...
Setting environment variables for accessing in PHP when using Apache
I have a Linux environment and I have a PHP Web Application that conditionally runs based on environment variables using getenv in PHP. I need to know how these environment variables need to be set for the application to work correctly. I am not sure how to set this up on Apache.
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Linking static libraries to other static libraries
I have a small piece of code that depends on many static libraries (a_1-a_n). I'd like to package up that code in a static library and make it available to other people.
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jQuery `.is(“:visible”)` not working in Chrome
...n appended to a
document since it depends on the applicable styles.
All option elements are considered hidden, regardless of their
selected state.
During animations that hide an element, the element is considered
visible until the end of the animation. During animations to show an
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Split column at delimiter in data frame [duplicate]
...b','b|c','x|y'))
library(splitstackshape)
cSplit(df, "FOO", "|")
# ID FOO_1 FOO_2
# 1 11 a b
# 2 12 b c
# 3 13 x y
This particular function also handles splitting multiple columns, even if each column has a different delimiter:
df <- data.frame(ID=11:13,
...
Parsing XML with namespace in Python via 'ElementTree'
...tTree is not too smart about namespaces. You need to give the .find(), findall() and iterfind() methods an explicit namespace dictionary. This is not documented very well:
namespaces = {'owl': 'http://www.w3.org/2002/07/owl#'} # add more as needed
root.findall('owl:Class', namespaces)
Prefixes a...