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C++ - passing references to std::shared_ptr or boost::shared_ptr
...p points to an object that cannot be destroyed during this function
}
So by using a reference to a shared_ptr, you disable that guarantee. So in your second case:
Class::only_work_with_sp(boost::shared_ptr<foo> &sp) //Again, no copy here
{
...
sp->do_something();
...
Delete all data in SQL Server database
...ECT TOP 1 [name] FROM sysobjects WHERE [type] = 'P' AND category = 0 ORDER BY [name])
WHILE @name is not null
BEGIN
SELECT @SQL = 'DROP PROCEDURE [dbo].[' + RTRIM(@name) +']'
EXEC (@SQL)
PRINT 'Dropped Procedure: ' + @name
SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [t...
Should I pass an std::function by const-reference?
...
If you want performance, pass by value if you are storing it.
Suppose you have a function called "run this in the UI thread".
std::future<void> run_in_ui_thread( std::function<void()> )
which runs some code in the "ui" thread, then signals...
Get object by id()? [duplicate]
Let's say I have an id of a Python object, which I retrieved by doing id(thing) . How do I find thing again by the id number I was given?
...
How to delete a row by reference in data.table?
My question is related to assignment by reference versus copying in data.table . I want to know if one can delete rows by reference, similar to
...
使用 XML 和 Web 服务 · App Inventor 2 中文网
...XML, it will signal an error and return the empty list.
The list returned by XMLTextDecode contains one pair for each top-level tag-delimited structure in the input string. For example, decoding
123
returns the list of one pair (hello, 123) and decoding
123
456
returns the list of two pair...
Finding duplicate values in a SQL table
...
SELECT
name, email, COUNT(*)
FROM
users
GROUP BY
name, email
HAVING
COUNT(*) > 1
Simply group on both of the columns.
Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY but this has changed with the idea of "functional depe...
LIMIT 10..20 in SQL Server
... is not part of standard SQL. It's supported as a vendor extension to SQL by MySQL, PostgreSQL, and SQLite.
Other brands of database may have similar features (e.g. TOP in Microsoft SQL Server), but these don't always work identically.
It's hard to use TOP in Microsoft SQL Server to mimic the L...
How do I find duplicate values in a table in Oracle?
...
Aggregate the column by COUNT, then use a HAVING clause to find values that appear greater than one time.
SELECT column_name, COUNT(column_name)
FROM table_name
GROUP BY column_name
HAVING COUNT(column_name) > 1;
...
What are the use(s) for tags in Go?
...for your own use.
As mentioned in the documentation of reflect.StructTag, by convention the value of a tag string is a space-separated list of key:"value" pairs, for example:
type User struct {
Name string `json:"name" xml:"name"`
}
The key usually denotes the package that the subsequent "va...