pattern-matching

问题 I have problem on db search with like and elastic search in Turkish upper and lower case. For example I have posts table which contains post titled 'DENEME YAZI' . If I run this query: select * from posts where title like '%deneme%'; or: select * from posts where title like '%YAZI%'; I get correct result but if I run: select * from posts where title like '%yazı%'; it doesn't return any record. My database encoding is tr_TR.UTF-8 . How can I get correct results without entering exact word? 回答1

问题 I am writing a String parser that I use to parse all strings from a text file, The strings can be inside single or double quotes, Pretty simple right? well not really. I wrote a regex to match strings how I want. but it's giving me StackOverFlow error on big strings (I am aware java isn't really good with regex stuff on big strings), This is the regex pattern (['"])(?:(?!\1|\\).|\\.)*\1 This works good for all the string inputs that I need, but as soon as theres a big string it throws

问题 In C# 7.1 the below is valid code: object o = new object(); switch (o) { case CustomerRequestBase c: //do something break; } However, I want to use the pattern switch statement in the following scenario: public T Process<T>(object message, IMessageFormatter messageFormatter) where T : class, IStandardMessageModel, new() { switch (T) { case CustomerRequestBase c: //do something break; } } The IDE gives me the error "'T' is a type, which is not valid in the given context" Is there an elegant

问题 In C# 7.1 the below is valid code: object o = new object(); switch (o) { case CustomerRequestBase c: //do something break; } However, I want to use the pattern switch statement in the following scenario: public T Process<T>(object message, IMessageFormatter messageFormatter) where T : class, IStandardMessageModel, new() { switch (T) { case CustomerRequestBase c: //do something break; } } The IDE gives me the error "'T' is a type, which is not valid in the given context" Is there an elegant

问题 I have a csv file that I download that contains 3 different tables on the same tab. I only need the top table and the bottom table but depending on when I download the file the number of rows vary. I have attached an image of the file below. CSV file with the 3 tables separated by blank rows What I am hoping to accomplish is reading the 1st table and the 3rd table as two separate dataframes. I was hoping to use grep/grepl to get DF1 up to the 1st break (row 202) and get DF2 starting after the

问题 In the documentation for std::iter::Iterator::filter() it explains that values are passed to the closure by reference, and since many iterators produce references, in that case the values passed are references to references. It offers some advice to improve ergonomics, by using a &x pattern to remove one level of indirection, or a &&x pattern to remove two levels of indirection. However, I've found that this second pattern does not compile if the item being iterated does not implement Copy :

问题 In the documentation for std::iter::Iterator::filter() it explains that values are passed to the closure by reference, and since many iterators produce references, in that case the values passed are references to references. It offers some advice to improve ergonomics, by using a &x pattern to remove one level of indirection, or a &&x pattern to remove two levels of indirection. However, I've found that this second pattern does not compile if the item being iterated does not implement Copy :

问题 What can ref do that references couldn't? Could match value.try_thing() { &Some(ref e) => do_stuff(e), // ... } not be equally expressed by match value.try_thing() { &Some(e) => do_stuff(&e), // ... } 回答1: No, it is not avoidable with your proposed syntax. Your syntax does not allow for taking a reference when otherwise a move would be permissable. In this example, inner is a copy of the integer from val and changing it has no effect on val : fn main() { let mut val = Some(42); if let &mut

问题 I want to switch through many possible cases for x and there's one case (here x == 0 ) where I want to check the result of some additional code to determine what to do next. One possibility is to return early from the match. I'd use break to do this early-returning in C, but this isn't allowed in Rust. return returns from the parent function (in this case main() ) and not from the match only (i.e. the println! at the end isn't run!). I could just negate the sub-condition (here y == 0 ) and

问题 I want to switch through many possible cases for x and there's one case (here x == 0 ) where I want to check the result of some additional code to determine what to do next. One possibility is to return early from the match. I'd use break to do this early-returning in C, but this isn't allowed in Rust. return returns from the parent function (in this case main() ) and not from the match only (i.e. the println! at the end isn't run!). I could just negate the sub-condition (here y == 0 ) and