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Performance surprise with “as” and nullable types
...ficient code, no value conversions have to be considered.
The is operator test is easy, just check if the object isn't null and is of the expected type, takes but a few machine code instructions. The cast is also easy, the JIT compiler knows the location of the value bits in the object and uses th...
计算统计特征（正态分布）函数及实例 - C/C++ - 清泛网 - 专注C/C++及内核技术
... <map>
int _tmain(int argc, _TCHAR* argv[])
{
std::map<int, int> map_test;
map_test[0] = 100;
map_test[5] = 80;
map_test[2] = 10;
map_test[8] = 99;
map_test[4] = 102;
StdevInfo stdev_info;
stdev_info.init();
stdev_info.caculate_stdev_info(map_test.begin(), map_test.end(),
...
Is 'switch' faster than 'if'?
...-- note that the compiler in practice would need to insert some form of if test around the table to ensure that the input was valid in the table. Note also that it only works in the specific case that the input is a run of consecutive numbers.
If the number of branches in a switch is extremely larg...
Why can't R's ifelse statements return vectors?
...ion for ifelse states:
ifelse returns a value with the same
shape as test which is filled with
elements selected from either yes or
no depending on whether the element
of test is TRUE or FALSE.
Since you are passing test values of length 1, you are getting results of length 1. If you p...
Postgres unique constraint vs index
...basic but important issue, so I decided to learn by example.
Let's create test table master with two columns, con_id with unique constraint and ind_id indexed by unique index.
create table master (
con_id integer unique,
ind_id integer
);
create unique index master_unique_idx on master (in...
Comparison of full text search engine - Lucene, Sphinx, Postgresql, MySQL?
...QL and index that table and it's entries.
1.Table Structure
CREATE TABLE test_solr_mysql
(
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
name VARCHAR(45) NULL,
created TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (id)
);
2.Populate the above table
INSERT INTO `test_solr_mysql` (`n...
Attach a file from MemoryStream to a MailMessage in C#
... (var message = new MailMessage("me@example.com", "you@example.com", "Just testing", "See attachment..."))
{
writer.WriteLine("Comma,Seperated,Values,...");
writer.Flush();
stream.Position = 0; // read from the start of what was written
message.Attachments.Add(new Attachment(str...
How to tell if a string contains a certain character in JavaScript?
...
I would go with /hello/g.test(your_string). While indexOf works, I think a regex test tells a better story of what you're trying to accomplish. If I'm trying to find a sequence of characters inside a string, the index is irrelevant.
...
Virtual Serial Port for Linux
I need to test a serial port application on Linux, however, my test machine only has one serial port.
8 Answers
...
Javascript: negative lookbehind equivalent?
...matches
const reverse = s => s.split('').reverse().join('');
const test = (stringToTests, reversedRegexp) => stringToTests
.map(reverse)
.forEach((s,i) => {
const match = reversedRegexp.test(s);
console.log(stringToTests[i], match, 'token:', match ? reverse(reversedRegexp.e...