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Convert a row of a data frame to vector
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Might have been changed in the meantime, but today unlist allows dropping names: identical(unlist(df[1,], use.names = FALSE), as.numeric(df[1,])) (and btw df still is not a sensible name for a data.frame... ;-))
– Andri Signorell
Sep 25 '1...
Undefined reference to `pow' and `floor'
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Look in /lib or /usr/lib. The libraries are all named lib<name>.a or lib<name>.so - it's the "<name>" you put after the -l. In this case, the math library is named libm.so, so we call it -lm.
– ams
Dec 29 '11 at ...
What does |= (ior) do in Python?
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edited Sep 24 at 0:32
answered Jan 9 '18 at 1:52
pyl...
Fastest way to determine if an integer's square root is an integer
... CPU (x86) and programming language (C/C++). Your results may vary, especially because I don't know how the Java factor will play out.
My approach is threefold:
First, filter out obvious answers. This includes negative numbers and looking at the last 4 bits. (I found looking at the last six di...
How to print a query string with parameter values when using Hibernate
...he the following categories:
org.hibernate.SQL - set to debug to log all SQL DML statements as they are executed
org.hibernate.type - set to trace to log all JDBC parameters
So a log4j configuration could look like:
# logs the SQL statements
log4j.logger.org.hibernate.SQL=debug
# Logs the...
std::enable_if to conditionally compile a member function
... I want to use std::enable_if to choose between two member-functions and allow only one of them to be used.
7 Answers
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How to find memory leak in a C++ code/project?
...e software tools
1
Understand the operator basics. The C++ operator new allocates heap memory. The delete operator frees heap memory. For every new, you should use a delete so that you free the same memory you allocated:
char* str = new char [30]; // Allocate 30 bytes to house a string.
delete ...
.NET data structures: ArrayList, List, HashTable, Dictionary, SortedList, SortedDictionary — Speed,
...d Visual Basic books talk about them to a certain extent, but they never really go into any real detail.
13 Answers
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How would I run an async Task method synchronously?
I'm learning about async/await, and ran into a situation where I need to call an async method synchronously. How can I do that?
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Check if a class has a member function of a given signature
...oid ReportMemUsage(const TMap& m, std::true_type)
{
// We may call used_memory() on m here.
}
template<typename TMap>
void ReportMemUsage(const TMap&, std::false_type)
{
}
template<typename TMap>
void ReportMemUsage(const TMap& m)
{
ReportMemUsage(m,
std:...