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• A compiler for automata theory

  - by saadtaame

  I'm designing a programming language for automata theory. My goal is to allow programmers to use machines (DFA, NFA, etc...) as units in expressions. I'm confused whether the language should be compiled, interpreted, or jit-compiled! My intuition is that compilation is a good choice, for some operations might take too much time (converting NFA's to equivalent DFA's can be expensive). Translating to x86 seems good. There is one issue however: I want the user to be able to plot machines. Any ideas?

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• Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

  - by Alex R

  And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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• What is the purpose of Java's unary plus operator?

  - by Syntactic

  Java's unary plus operator appears to have come over from C, via C++. As near as I can tell, it has the following effects: promotes its operand to int, if it's not already an int or wider unboxes its operand, if it's a wrapper object complicates slightly the parsing of evil expressions containing large numbers of consecutive plus signs It seems to me that there are better (or, at least, clearer) ways to do all of these things. In this SO question, concerning the counterpart operator in C#, someone said that "It's there to be overloaded if you feel the need." But in Java, one cannot overload any operator. So does this operator exist in Java just because it existed in C++?

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• Can a Domain Specific Language (DSL) be localized?

  - by michielvoo

  I have never written a DSL, but I am considering it as a feature for a new project (hypothetical). It would be for end users to be able to express in natural language concepts such as weekdays between 10 and 11 except on the first monday of the month. Dutch users might write weekdagen tussen 10 en 11 behalve op de eerste maandag van de maand. In this case the position of the words seems to match, but there may be expressions where the position of verbs/nouns etc. could be different between languages. I realise the obvious answer (it depends). I am a .NET developer and I consider using Boo but I'm open to suggestions. I need to understand wether each translation requires rewriting a part of the implementation (which part) or if there is a way to do actual translations, maybe in some sort of preprocessor. Thanks!

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• Adding two Set[Any]

  - by Alex Boisvert

  Adding two Set[Int] works: Welcome to Scala version 2.8.1.final (Java HotSpot(TM) Server VM, Java 1.6.0_23). Type in expressions to have them evaluated. Type :help for more information. scala> Set(1,2,3) ++ Set(4,5,6) res0: scala.collection.immutable.Set[Int] = Set(4, 5, 6, 1, 2, 3) But adding two Set[Any] doesn't: scala> Set[Any](1,2,3) ++ Set[Any](4,5,6) <console>:6: error: ambiguous reference to overloaded definition, both method ++ in trait Addable of type (xs: scala.collection.TraversableOnce[Any])scala.collection.immutable.Set[Any] and method ++ in trait TraversableLike of type [B >: Any,That](that: scala.collection.TraversableOnce[B])(implicit bf: scala.collection.generic.CanBuildFrom[scala.collection.immutable.Set[Any],B,That])That match argument types (scala.collection.immutable.Set[Any]) Set[Any](1,2,3) ++ Set[Any](4,5,6) ^ Any suggestion to work around this error?

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• scala REPL is slow on vista

  - by Jacques René Mesrine

  I installed scala-2.8.0.RC3 by extracting the tgz file into my cygwin (vista) home directory. I made sure to set $PATH to scala-2.8.0.RC3/bin. I start the REPL by typing: $ scala Welcome to Scala version 2.8.0.RC3 (Java HotSpot(TM) Client VM, Java 1.6.0_20). Type in expressions to have them evaluated. Type :help for more information. scala> Now when I tried to enter an expression scala> 1 + 'a' the cursor hangs there without any response. Granted that I have chrome open with a million tabs and VLC playing in the background, but CPU utilization was 12% and virtual memory was about 75% utilized. What's going on ? Do I have to set the CLASSPATH or perform other steps.

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• How would you parse the location text from Twitter to get the latitude/longitude in Objective-C?

  - by Brennan

  The location text from Twitter could be just about anything. Sometimes Twitter clients set the location with the user's latitude and longitude in the following format. "\U00dcT: 43.05948,-87.908409" Since there is no built-in support for Regular Expressions in Objective-C I am considering using the NSString functions like rangeOfString to pull the float values out of this string. For my current purpose I know the values with start with 43 and 87 so I can key off those values this time but I would prefer to do better than that. What would you do to parse the latitude/longitude from this string?

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• Struts/JSP/J2EE performance and memory profiling and issues

  - by Berlin Brown

  We are using Struts and having performance issues. And making heavy use of jsp includes, tiles, EL expressions. I am sure this is eating up a lot of memory and processing time. What are some approaches to profile the JSP page? What tools could I use? What should I look for when profiling? I have seen the code generated JSP Java Servlet Code and I see the bottlenecks but would rather measure it more accurately. This is under JDK1.5 and IBM Websphere 6.1 (RAD7)

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• What's the point of lambda in scheme?

  - by incrediman

  I am learning scheme. I know how to use both lambda and let expressions. However I'm struggling to figure out what the point is of using lambda. Can't you do everything with let that you can with lambda? It would be especially helpful to see an example of a situation where a lambda expression is a better choice than let. One other thing - are there also situations where let is more useful than lambda? If so such an example would be nice as well. Thanks!

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• How to validate expression on button click in asp.net C#

  - by Hamad

  I am making a website and I have made a form fields like email field and validation expressions associated with it. Validation is initiated on text change. But i want it t execute on "submit" button click event. I have searched but could not locate the solution to my problem. Please tel me why is this happening and how can i make it right. I am new to this web development field, So need help from you guys. Thanks in advance!!! Hamad

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• How do I use Eval() to reference values in a SortedDictionary in an asp Repeater?

  - by MatthewMartin

  I thought I was clever to switch from the memory intensive DataView to SortedDictionary as a memory efficient sortable data structure. Now I have no idea how get the key and value out of the datasource in the <%# or Eval() expressions. SortedDictionary<int, string> data = RetrieveNames(); rCurrentTeam.DataSource = data; rCurrentTeam.DataBind(); <asp:Repeater ID="rNames" runat="server"> <ItemTemplate> <asp:Label ID="lblName" runat="server" Text='<%# Eval("what?") %>' /> </ItemTemplate> </asp:Repeater> Any suggestions?

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• Selecting a specific div from a extern webpage using CURL

  - by Paulo

  Hi can anyone help me how to select a specific div from the content of a webpage. Say i want to get the div with id="body" from webpage http://www.test.com/page3.php My current code looks something like this: (not working) //REG EXP. $s_searchFor = '@^/.dont know what to put here..@ui'; //CURL $ch = curl_init(); $timeout = 5; // set to zero for no timeout curl_setopt ($ch, CURLOPT_URL, 'http://www.test.com/page3.php'); curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout); if(!preg_match($s_searchFor, $ch)) { $file_contents = curl_exec($ch); } curl_close($ch); // display file echo $file_contents; So i'd like to know how i can use reg expressions to find a specific div and how to unset the rest of the webpage so that $file_content only contains the div.

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• apache mod_rewrite regex problem with multiple parameter

  - by iko

  Regular expressions have always been my pet peeves. Every time I think that I finally got it I have a new problem ! I want to catch url like this : http://www.mydomain.com/boutique/blabla-1/bla-bla2/99/104 http://www.mydomain.com/boutique/blabla1/99 and eventually : http://www.mydomain.com/boutique/blabla-1/bla-bla2/product1/99/104/55/ after a lot of tries and errors I came up with this which seems to work with http://www.gskinner.com/RegExr/ but not in apache ^.*/boutique/([a-zA-Z-]*)(/?[a-zA-Z-]*)/?([0-9]*)/?([0-9]*)/?$ boutique.php?c1=$3&c2=$4 (I was only working with the first two url so far) MY apache rewrite log debug files are helpless : pass through /Users/iko/Sites/mysite/boutique.php I'm only interrested in getting the ids. Any help we'll be welcomed ! Thank you.

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• Pros and Cons of Different macro function / inline methods in C

  - by Robert S. Barnes

  According to the C FAQ, there are basically 3 practical methods for "inlining" code in C: #define MACRO(arg1, arg2) do { \ /* declarations */ \ stmt1; \ stmt2; \ /* ... */ \ } while(0) /* (no trailing ; ) */ or #define FUNC(arg1, arg2) (expr1, expr2, expr3) To clarify this one, the arguments are used in the expressions, and the comma operator returns the value of the last expression. or using the inline declaration which is supported as an extension to gcc and in the c99 standard. The do { ... } while (0) method is widely used in the Linux kernel, but I haven't encountered the other two methods very often if at all. I'm referring specifically to multi-statement "functions", not single statement ones like MAX or MIN. What are the pros and cons of each method, and why would you choose one over the other in various situations?

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• which regular expression will capture this sequence?

  - by John Smith

  The text follows this pattern <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) <tr class="text" (any sequence of characters here, except ABC)ABC(any sequence of characters here, except ABC) so basically the above line might repeat itself multiple times, and the idea is to retrieve the first 3 characters immediately after ABC. I have tried regular expressions along the lines of \<tr class="text" [.]+ABC(?<capture>[.]{3}) but they all fail. Can someone give me a hint?

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• Expression.OrElse, dynamically creating a condition.

  - by Jim

  Hi, I am attempting to create a dynamic where clause using the standard expression API. var query = ( from p in Parties orderby p.PartyId orderby p.FullName select p ).AsQueryable(); Expression<Func<Party, bool>> @fn = (p) => SqlMethods.Like(p.FullName, "%smith%") || SqlMethods.Like(p.Person.FirstName, "%smith%"); Expression<Func<Party, bool>> @sn = (p) => SqlMethods.Like(p.Person.FirstName, words[0]); ParameterExpression pe = Expression.Parameter(typeof(Party), "p"); Expression orelse = Expression.OrElse( Expression.Lambda(@fn, pe), Expression.Lambda(@sn, pe) ); The expressions above will ultimately be added to a where clause. I need to add a bunch of 'likes'. How do I do this? I get InvalidOperationException on the operator OrElse I have also tried Expression.Or Thanks Regards Craig.

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• How to read a file with variable multi-row data in Python

  - by dr.bunsen

  I have a file that is about 100Mb that looks like this: #meta data 1 skadjflaskdjfasljdfalskdjfl sdkfjhasdlkgjhsdlkjghlaskdj asdhfk #meta data 2 jflaksdjflaksjdflkjasdlfjas ldaksjflkdsajlkdfj #meta data 3 alsdkjflasdjkfglalaskdjf This file contains one row of meta data that corresponds to several, variable length data containing only alpha-numeric characters. What is the best way to read this data into a simple list like this: data = [[#meta data 1, skadjflaskdjfasljdfalskdjflsdkfjhasdlkgjhsdlkjghlaskdjasdhfk], [#meta data 2, jflaksdjflaksjdflkjasdlfjasldaksjflkdsajlkdfj], [#meta data 3, alsdkjflasdjkfglalaskdjf]] My initial idea was to use the read() method to read the whole file into memory and then use regular expressions to parse the data into the desired format. Is there a better more pythonic way? All metadata lines start with an octothorpe and all data lines are all alpha-numeric. Thanks!

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• Python: Elegant way to check if at least one regex in list matches a string

  - by houbysoft

  Hi. I have a list of regexes in python, and a string. Is there an elegant way to check if the at least one regex in the list matches the string? By elegant, I mean something better than simply looping through all of the regexes and checking them against the string and stopping if a match is found. Basically, I had this code: list = ['something','another','thing','hello'] string = 'hi' if string in list: pass # do something else: pass # do something else Now I would like to have some regular expressions in the list, rather than just strings, and I am wondering if there is an elegant solution to check for a match to replace if string in list:. Thanks in advance.

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• update columns when value is numeric in tsql

  - by knittl

  i want to normalize date fields from an old badly designed db dump. i now need to update every row, where the datefield only contains the year. update table set date = '01.01.' + date where date like '____' and isnumeric(date) = 1 and date >= 1950 but this will not work, because sql does not do short circuit evaluation of boolean expressions. thus i get an error "error converting nvarchar '01.07.1989' to int" is there a way to work around this? the column also contains strings with a length of 4, which are not numbers (????, 5/96, 70/8, etc.) the table only has 60000 rows

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• Why is this logical expression in python False?

  - by W3ctor

  My question is, why are these expressions False? Python 2.6.4 (r264:75706, Dec 7 2009, 18:45:15) [GCC 4.4.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> num = raw_input("Choose a number: ") Choose a number: 5 >>> print num 5 >>> print ( num < 18 ) False >>> print ( num == 5 ) False Because if i try this: >>> print ( num > 0 ) True The expression works fine. Thank you for the help!

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• Permanently write variables to a php file with php

  - by Oliver

  I need to be able to permanently change variables in a php file using php. I am creating a multilanguage site using codeigniter and using the language helper which stores the text in php files in variables in this format: $lang['title'] = "Stuff"; I've been able to access the plain text of the files using fopen() etc and I it seems that I could probably locate the areas I want to edit with with regular expressions and rewrite the file once I've made the changes but it seems a bit hacky. Is there any easy way to edit these variables permanently using php? Cheers

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• How to replace for-loops with a functional statement in C#?

  - by Lernkurve

  A colleague once said that God is killing a kitten every time I write a for-loop. When asked how to avoid for-loops, his answer was to use a functional language. However, if you are stuck with a non-functional language, say C#, what techniques are there to avoid for-loops or to get rid of them by refactoring? With lambda expressions and LINQ perhaps? If so, how? Questions So the question boils down to: Why are for-loops bad? Or, in what context are for-loops to avoid and why? Can you provide C# code examples of how it looks before, i.e. with a loop, and afterwards without a loop?

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• Is it a solvable problem to generate a regular expression that matches some input set?

  - by Roman

  I provide some input set which contains known separated number of text blocks. I want to make a program that automatically generate 1 or more regular expressions each of which matches every text block in the input set. I see some relatively easy ways to implement a brute-force search. But I'm not an expert in compilers theory. That's why I'm curious: 1) is this problem solvable? or there are some principle impossibility to make such algorithm? 2) is it possible to achieve polynomial complexity for this algorithm and avoid brute forcing?

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• prolog to solve grammar involving braces

  - by Abhilash Muthuraj

  I'm trying to solve DCG grammar in prolog and succeeded upto a point, i'm stuck in evaluating the expressions involving braces like these. expr( T, [’(’, 5, +, 4, ’)’, *, 7], []), expr(Z) --> num(Z). expr(Z) --> num(X), [+], expr(Y), {Z is X+Y}. expr(Z) --> num(X), [-], expr(Y), {Z is X-Y}. expr(Z) --> num(X), [*], expr(Y), {Z is X*Y}. num(D) --> [D], {number(D)}. eval(L, V, []) :- expr(V, L, []).

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• Regex and unicode

  - by dbr

  I have a script that parses the filenames of TV episodes (show.name.s01e02.avi for example), grabs the episode name (from the www.thetvdb.com API) and automatically renames them into something nicer (Show Name - [01x02].avi) The script works fine, that is until you try and use it on files that have Unicode show-names (something I never really thought about, since all the files I have are English, so mostly pretty-much all fall within [a-zA-Z0-9'\-]) How can I allow the regular expressions to match accented characters and the likes? Currently the regex's config section looks like.. config['valid_filename_chars'] = """0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@£$%^&*()_+=-[]{}"'.,<>`~? """ config['valid_filename_chars_regex'] = re.escape(config['valid_filename_chars']) config['name_parse'] = [ # foo_[s01]_[e01] re.compile('''^([%s]+?)[ \._\-]\[[Ss]([0-9]+?)\]_\[[Ee]([0-9]+?)\]?[^\\/]*$'''% (config['valid_filename_chars_regex'])), # foo.1x09* re.compile('''^([%s]+?)[ \._\-]\[?([0-9]+)x([0-9]+)[^\\/]*$''' % (config['valid_filename_chars_regex'])), # foo.s01.e01, foo.s01_e01 re.compile('''^([%s]+?)[ \._\-][Ss]([0-9]+)[\.\- ]?[Ee]([0-9]+)[^\\/]*$''' % (config['valid_filename_chars_regex'])), # foo.103* re.compile('''^([%s]+)[ \._\-]([0-9]{1})([0-9]{2})[\._ -][^\\/]*$''' % (config['valid_filename_chars_regex'])), # foo.0103* re.compile('''^([%s]+)[ \._\-]([0-9]{2})([0-9]{2,3})[\._ -][^\\/]*$''' % (config['valid_filename_chars_regex'])), ]

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