大约有 48,000 项符合查询结果（耗时：0.0780秒） [XML]
Count number of objects in list [closed]
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length(x)
Get or set the length of vectors (including lists) and factors, and of any other R object for which a method has been defined.
lengths(x)
Get the length of each element of a list or atomic vector (is.atomic) as an integer or numeric vector.
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Why is there no logical xor in JavaScript?
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JavaScript traces its ancestry back to C, and C does not have a logical XOR operator. Mainly because it's not useful. Bitwise XOR is extremely useful, but in all my years of programming I have never needed a logical XOR.
If you have two boolean variables you can mim...
Remove HTML Tags from an NSString on the iPhone
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A quick and "dirty" (removes everything between < and >) solution, works with iOS >= 3.2:
-(NSString *) stringByStrippingHTML {
NSRange r;
NSString *s = [[self copy] autorelease];
while ((r = [s rangeOfString:@"<[...
Google Maps: how to get country, state/province/region, city given a lat/long value?
...e. I need to store this information in a manner that hierarchy is preserve and without duplicates (e.g. "USA" and "United States" and "United States of America" are the same country; I only want one instance of this country in my database).
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Format SQL in SQL Server Management Studio
...h complete T-SQL batch/script support (any DDL, any DML), SSMS Plugin, command-line bulk formatter, and other options.
It's available for immediate/online use at http://poorsql.com, and just today graduated to "version 1.0" (it was in beta version for a few months), having just acquired support for...
How to extract a substring using regex
... modifier, so that for this 'is' my 'data' with quotes it would stop early and return is instead of matching as many characters as possible and return is' my 'data, which is the default behavior.
– Timekiller
Sep 12 '16 at 14:08
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How to pass arguments into a Rake task with environment in Rails? [duplicate]
...ironment using the :needs option. For example:
desc "Testing environment and variables"
task :hello, :message, :needs => :environment do |t, args|
args.with_defaults(:message => "Thanks for logging on")
puts "Hello #{User.first.name}. #{args.message}"
end
Updated per @Peiniau's comment...
Using Regular Expressions to Extract a Value in Java
...blic static void main(String[] args) {
// create matcher for pattern p and given string
Matcher m = p.matcher("Testing123Testing");
// if an occurrence if a pattern was found in a given string...
if (m.find()) {
// ...then you can use group() methods.
System.out.prin...
How to find server name of SQL Server Management Studio
...tance. To connect to it in Management Studio, just type . (dot) OR (local) and click Connect. If the instance name is different, then use .\[instance name] to connect to it (for example if the instance name is SQL2008, connect to .\SQL2008).
Also make sure SQL Server and SQL Server Browser services...
Update MongoDB field using value of another field
...ion 4.2+ which allows using of aggregation pipeline in the update document and the updateOne, updateMany or update collection method. Note that the latter has been deprecated in most if not all languages drivers.
MongoDB 4.2+
Version 4.2 also introduced the $set pipeline stage operator which is an...