pattern-matching

问题 I'm trying to use pattern matching to write a calculator application. Two major types defined as below: type key = Plus | Minus | Multi | Div | Equals | Digit of int;; type state = { lcd: int; (* last computation done *) lka: key; (* last key actived *) loa: key; (* last operation actived *) vpr: int (* value print on the screen *) };; let print_state s = match s with state (a,_,_,d) -> print_int a; //Here has the compile error print_newline(); print_int d; print_newline();; However, if I

问题 I am very new to regex , Using python re i am looking to extract phone numbers from the following multi-line string text below : Source = """<p><strong>Kuala Lumpur</strong><strong>:</strong> +60 (0)3 2723 7900</p> <p><strong>Mutiara Damansara:</strong> +60 (0)3 2723 7900</p> <p><strong>Penang:</strong> + 60 (0)4 255 9000</p> <h2>Where we are </h2> <strong> Call us on:</strong> +6 (03) 8924 8686 </p></div><div class="sys_two"> <h3 class="parentSchool">General enquiries</h3><p style="FONT-SIZE

问题 Everybody says that pattern matching is a great feature in functional languages. Why? Can't I simple use ifs and switch cases for everything? I'd like to understand the advantages of using pattern matching instead of regular procedural programming ifs and switch cases 回答1: I'd first like to note that you don't use pattern matching "instead" of switch statements. Scala doesn't have switch statements, what it does have is match blocks, with cases inside that superficially look very similar to a

问题 Everybody says that pattern matching is a great feature in functional languages. Why? Can't I simple use ifs and switch cases for everything? I'd like to understand the advantages of using pattern matching instead of regular procedural programming ifs and switch cases 回答1: I'd first like to note that you don't use pattern matching "instead" of switch statements. Scala doesn't have switch statements, what it does have is match blocks, with cases inside that superficially look very similar to a

问题 I have read that the Longest Common Prefix (LCP) could be used to find the number of occurrences of a pattern in a string. Specifically, you just need to create the suffix array of the text, sort it, and then instead of doing binary search to find the range so that you can figure out the number of occurrences, you simply compute the LCP for each successive entry in the suffix array. Although using binary search to find the number of occurrences of a pattern is obvious I can't figure out how

问题 In scala.util.matching.Regex trait MatchData I see that there support for groupnames , I thought that this was related to (Regex Named Capturing Groups) But since Java does not support groupnames until version 7 as I understand it (ref), Scala version 2.8.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6. gives me this exception: scala> val pattern = """(?<login>\w+) (?<id>\d+)""".r java.util.regex.PatternSyntaxException: Look-behind group does not have an obvio us maximum length near index 11 (

问题 In scala.util.matching.Regex trait MatchData I see that there support for groupnames , I thought that this was related to (Regex Named Capturing Groups) But since Java does not support groupnames until version 7 as I understand it (ref), Scala version 2.8.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6. gives me this exception: scala> val pattern = """(?<login>\w+) (?<id>\d+)""".r java.util.regex.PatternSyntaxException: Look-behind group does not have an obvio us maximum length near index 11 (

问题 I'm learning about regular expression. I don't know how to combine different regular expression to make a single generic regular expression. I want to write a single regular expression which works for multiple cases. I know this is can be done with naive approach by using or " | " operator. I don't like this approach. Can anybody tell me better approach? 回答1: You need to compile all your regex functions. Check this example: import re re1 = r'\d+\.\d*[L][-]\d*\s[A-Z]*[/]\d*' re2 = '\d*[/]\d*[A

问题 I'm trying to understand Pattern.quote using the following code: String pattern = Pattern.quote("1252343% 8 567 hdfg gf^$545"); System.out.println("Pattern is : "+pattern); produces the output: Pattern is : \Q1252343% 8 567 hdfg gf^$545\E What are \Q and \E here? The documentation description says : Returns a literal pattern String for the specified String . This method produces a String that can be used to create a Pattern that would match the string s as if it were a literal pattern.

问题 How to save all text with replaced text. At now save only replaced text I want to change only 9752951c-0392-71e1-01a3- ac10016b0000 in txt 1.txt text ... <URL>http://bs.com/opr-console/rest/9.10/event_list/9752951c-0392-71e1-01a3- ac10016b0000</URL> <method>PUT</method> <auth-methods>DIGEST</auth-methods> <auth-preemptive>true</auth-preemptive> <auth-username>admin</auth-username> <auth-password>rO0ABXQABWFkbWlu</auth- .....bla-bla-la.. vbs script: Dim objExec, objShell, objWshScriptExec,