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  • Derivative of a Higher-Order Function

    - by Claudiu
    This is in the context of Automatic Differentiation - what would such a system do with a function like map, or filter - or even one of the SKI Combinators? Example: I have the following function: def func(x): return sum(map(lambda a: a**x, range(20))) What would its derivative be? What will an AD system yield as a result? (This function is well-defined on real-number inputs).

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  • T-SQL String Functions: difference between using Left/Right and Substring and strange behaviour

    - by TheObserver
    I am using SQL Server 2008 & 2005 (Express). I'm trying to extract part of an alpha numeric string from a varchar field. RIGHT(str_field,3) yields null values but substring(str_field, len(str_field)-2, len(str_field)) gives the right value. left(str_field,7) gives the expected values. What gives? I would have thought that RIGHT(str_field,3) and substring(str_field, len(str_field)-2, len(str_field)) are equivalent expressions.

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  • problem with a join

    - by Luca Romagnoli
    I have this code: int se = (int) settings.GruppoSegreteria; var acc = db.USR_Accounts.Where( p => p.ID_Gruppo == se); var segreterie = from s in db.USR_Utenti join h in acc on s.ID equals h.USR_UtentiReference select s; And this error: The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join' I don't understand it. Can you help me? thanks

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  • Need Flex Regex Validation Expression for password that allows for only alphanumeric values and requ

    - by BlueDude
    Hi I'm trying to setup a RegexpValidator that only accepts a string of alphanumeric characters between 6-30 characters long and requires one number. I'm new to Regular Expressions and everything I've tried seems to keep returning an invalid ValidationRsultEvent. Here's a chunk of code: <mx:RegExpValidator id="regexValidator" source="{passwordInput}" property="text" triggerEvent="" valid="onPasswordValidate(event)" invalid="onPasswordValidate(event)" /> private function validateRegister():void { regexValidator.expression = "^(?=.*(\d|\W)).{6,30}$"; regexValidator.validate(); }

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  • Ignoring Whitespace with Regex(perl)

    - by Zerobu
    Hello, I am using Perl Regular expressions. How would i go about ignoring white space and still perform a test to see if a string match. For example. $var = " hello "; #I want var to igonore whitespace and still match if($var =~ m/hello/) { }

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  • Hidden features of C#3.5 [closed]

    - by xyz
    Possible Duplicate: Hidden Features of C#? Kindly donot mistake this question with Hidden Features of C#?. It is specific to C# 3.5 / dot net 3.5 I have figured out some(what I have used so far). They are as under 1) Linq 2(Objects, Sql, Xml) 2) Lambda expressions 3) Extention methods 4) Object initializers 5) Collection initialisers 6) Anonymous delegates 7)Automatic properties Please help me in finding out more. Thanks

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  • How to test if a gawk string contain a number?

    - by Tim Menzies
    In gawk I know two ways to test if a string contains a number. Which is best? Method one: using regular expressions: function method1(x) { return x ~ /^[+-]?([0-9]+[.]?[0-9]*|[.][0-9]+)([eE][+-]?[0-9]+)?$/ } Method two: the coercion trick (simpler): function method2(x) { return (x != "") && (x+0 == x) } Is there any reason to favor the more complex method1 over the simpler method2?

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  • PHP Application check name is unique if not append

    - by user270797
    My application requires the user to enter their business name, which the application will automatically create into a unique identifier to be used in URLs, ie "Bob's Cafe" will become "bobs-cafe" But if there are duplicate names I would like the application to add a number so if there is already a "bobs-cafe" we will use "bobs-cafe-1" and likewise if there is already a "bobs-cafe-1" we will use "bobs-cafe-2" Ive used explode and also looked at a regular expressions but I dont know the best way to approach this. Im stuck in being able to grab the number and incrementing it and returning the string

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  • Using two struts2 taglibs in each other

    - by Milad.KH
    Hi I want to use two struts taglib in each other, something like this: < s:properties value="url-< s:properties value="number"/"/ or < s:properties value="url-${number}"/ but I got the following error in the second one: According to TLD or attribute directive in tag file, attribute values does not accept any expressions. Anybody has a solution ? Thanks

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  • Built-in precedence in Expression Trees?

    - by jdk
    I'm unable to find the .NET FCL built-in concept of precedence to leverage while constructing Expression Trees. Ref System.Linq.Expressions Namespace. Is this something that must be handled manually in code, or is it somehow implicit and I'm not recognizing it? Maybe through helper methods or classes? I want to apply it to math operations to ensure 3 + 5 * 10 results in 53 instead of 80.

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  • Rails: three most recent comments with unique users

    - by Dennis Collective
    what would I put in the named scope :by_unique_users so that I can do Comment.recent.by_unique_users.limit(3), and only get one comment per user? class User has_many :comments end class Comment belongs_to :user named_scope :recent, :order => 'comments.created_at DESC' named_scope :limit, lambda { |limit| {:limit => limit}} named_scope :by_unique_users end on sqlite named_scope :by_unique_user, :group = "user_id" works, but makes it freak out on postgres, which is deployed on production PGError: ERROR: column "comments.id" must appear in the GROUP BY clause or be used in an aggregate function

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  • Regex to use each letter only once?

    - by gtcaz
    Is it possible to construct a PCRE-style regular expression that will only match each letter in a list only once? For example, if you have the letters "lrsa" and you try matching a word list against: ^[lrsa]*m[lrsa]*$ you're going to match "lams" (valid), but also "lamas" (invalid for our purposes because you only had one "a"). If your letter set was "lrsaa", you would want to match "lamas". Is this possible with regular expressions, or should I handle it programmatically?

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  • Using Squeak from a shell

    - by Vijay Mathew
    Can I launch Squeak as a REPL (no GUI), where I can enter and evaluate Smalltalk expressions? I know the default image don't allow this. Is there any documentation on how to build a minimum image that can be accessed from a command-line shell?

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  • regular expression help

    - by JPro
    I always get confused using regular expressions. Can anyone please suggest me a tutorial? I need help with checking for a string which, cannot contain any wild characters except colon, comma, full stop. It will be better to replace these if found. Any help? Thanks.

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  • wildcards to use in codeigniter routing?

    - by ajsie
    in codeigniter you can use wildcard to reroute. i never heard the word wildcards before. is this a set of rules you can use like regexp? cause in codeigniter documentation they just gave some examples eg. $route['product/(:num)'] = "catalog/product_lookup_by_id/$1"; is there a list/reference with all the available wildcard expressions you can use?

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  • Getting started with nbehave

    - by dotnetdev
    Hi, I am looking at using BDD, however, when evaluating the stories/conditions I write (using nBehave), how do I check if the story passes? Do I write another library with test methods? For example, if I want to test a site for having a link called "About", do I write a method which can check this and then another method in another class library which can call the method to check the link via lambda syntax and add the relevant test and bdd attributes? Thanks

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  • Parsing language for both binary and character files

    - by Thorsten S.
    The problem: You have some data and your program needs specified input. For example strings which are numbers. You are searching for a way to transform the original data in a format you need. And the problem is: The source can be anything. It can be XML, property lists, binary which contains the needed data deeply embedded in binary junk. And your output format may vary also: It can be number strings, float, doubles.... You don't want to program. You want routines which gives you commands capable to transform the data in a form you wish. Surely it contains regular expressions, but it is very good designed and it offers capabilities which are sometimes much more easier and more powerful. Something like a super-grep which you can access (!) as program routines, not only as tool. It allows: joining/grouping/merging of results inserting/deleting/finding/replacing write macros which allows to execute a command chain repeatedly meta-grouping (lists-tables-hypertables) Example (No, I am not looking for a solution to this, it is just an example): You want to read xml strings embedded in a binary file with variable length records. Your tool reads the record length and deletes the junk surrounding your text. Now it splits open the xml and extracts the strings. Being Indian number glyphs and containing decimal commas instead of decimal points, your tool transforms it into ASCII and replaces commas with points. Now the results must be stored into matrices of variable length....etc. etc. I am searching for a good language / language-design and if possible, an implementation. Which design do you like or even, if it does not fulfill the conditions, wouldn't you want to miss ? EDIT: The question is if a solution for the problem exists and if yes, which implementations are available. You DO NOT implement your own sorting algorithm if Quicksort, Mergesort and Heapsort is available. You DO NOT invent your own text parsing method if you have regular expressions. You DO NOT invent your own 3D language for graphics if OpenGL/Direct3D is available. There are existing solutions or at least papers describing the problem and giving suggestions. And there are people who may have worked and experienced such problems and who can give ideas and suggestions. The idea that this problem is totally new and I should work out and implement it myself without background knowledge seems for me, I must admit, totally off the mark.

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  • SED: Matching on 2 patterns on the same line

    - by Brian Knott
    Hi I want to delete a line using sed if it matches 2 regular expressions in the same line. EG the line starts with /* and end with */ (comment). The following script will do most of that. sed -e '/^\/*/ d' -e '/*\/$/ d' filename This script will remove all lines that start with * and end with */. I want it to remove the line only if is meets both criteria not one.

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