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  • How to see if type is instance of a class in Haskell?

    - by Raekye
    I'm probably doing this completely wrong (the unhaskell way); I'm just learning so please let me know if there's a better way to approach this. Context: I'm writing a bunch of tree structures. I want to reuse my prettyprint function for binary trees. Not all trees can use the generic Node/Branch data type though; different trees need different extra data. So to reuse the prettyprint function I thought of creating a class different trees would be instances of: class GenericBinaryTree a where is_leaf :: a -> Bool left :: a -> a node :: a -> b right :: a -> a This way they only have to implement methods to retrieve the left, right, and current node value, and prettyprint doesn't need to know about the internal structure. Then I get down to here: prettyprint_helper :: GenericBinaryTree a => a -> [String] prettyprint_helper tree | is_leaf tree = [] | otherwise = ("{" ++ (show (node tree)) ++ "}") : (prettyprint_subtree (left tree) (right tree)) where prettyprint_subtree left right = ((pad "+- " "| ") (prettyprint_helper right)) ++ ((pad "`- " " ") (prettyprint_helper left)) pad first rest = zipWith (++) (first : repeat rest) And I get the Ambiguous type variable 'a0' in the constraint: (Show a0) arising from a use of 'show' error for (show (node tree)) Here's an example of the most basic tree data type and instance definition (my other trees have other fields but they're irrelevant to the generic prettyprint function) data Tree a = Branch (Tree a) a (Tree a) | Leaf instance GenericBinaryTree (Tree a) where is_leaf Leaf = True is_leaf _ = False left (Branch left node right) = left right (Branch left node right) = right node (Branch left node right) = node I could have defined node :: a -> [String] and deal with the stringification in each instance/type of tree, but this feels neater. In terms of prettyprint, I only need a string representation, but if I add other generic binary tree functions later I may want the actual values. So how can I write this to work whether the node value is an instance of Show or not? Or what other way should I be approaching this problem? In an object oriented language I could easily check whether a class implements something, or if an object has a method. I can't use something like prettyprint :: Show a => a -> String Because it's not the tree that needs to be showable, it's the value inside the tree (returned by function node) that needs to be showable. I also tried changing node to Show b => a -> b without luck (and a bunch of other type class/preconditions/whatever/I don't even know what I'm doing anymore).

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  • Can I create template-based library objects in Dreamweaver CS5?

    - by Danjah
    At work we need two 'streams' of template. The first are general layout templates, like the ones already available in the MX through CS5 packages (except we'd have our own customised ones). The second are more granular objects, some of which are functional. In both cases, I don't want Jimmy to be able to wreak havoc inside anything other than the 'editable regions' which make up the templates. Now this is fine if I stick with the first scenario (layout templates) where there's simply a big chunk of editable region for good ole Jim to sprawl into, think of this as the 'body content' area. But I really do need these granular library (or snippet) objects to work in the same way. Unfortunately with my attempts so far they don't work as I'd have thought - perhaps for good reason? When I create a blank template and throw in my chunk of HTML (unobstrusive JS and external CSS use selectors in this HTML to provide style and function) and save it as a new library item or snippet, all looks well. Then I create a new document based on a layout template and save it as a plain html file (still all good so far). Next I drop in my custom library item... still all good... but then I go to save the document and it only allows me to save it as a new template! I expected it would just allow me to save it as HTML and have it simply respect the defined editable regions, as happens in the containing page 'body content' editable region. Apologies if that got specific and technical quite quickly, but it is quite particular. If you want some example files lemme know and I'll zip some up. Many thanks :) p.s It is not a requirement that library objects must somehow inject their dependency files into the newly created page - I already know what they'll be. Also, I know I must 'detatch from original' once I drop a library item into a document which then allows customisation of the library object.

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  • Basis of definitions

    - by Yttrill
    Let us suppose we have a set of functions which characterise something: in the OO world methods characterising a type. In mathematics these are propositions and we have two kinds: axioms and lemmas. Axioms are assumptions, lemmas are easily derived from them. In C++ axioms are pure virtual functions. Here's the problem: there's more than one way to axiomatise a system. Given a set of propositions or methods, a subset of the propositions which is necessary and sufficient to derive all the others is called a basis. So too, for methods or functions, we have a desired set which must be defined, and typically every one has one or more definitions in terms of the others, and we require the programmer to provide instance definitions which are sufficient to allow all the others to be defined, and, if there is an overspecification, then it is consistent. Let me give an example (in Felix, Haskell code would be similar): class Eq[t] { virtual fun ==(x:t,y:t):bool => eq(x,y); virtual fun eq(x:t, y:t)=> x == y; virtual fun != (x:t,y:t):bool => not (x == y); axiom reflex(x:t): x == x; axiom sym(x:t, y:t): (x == y) == (y == x); axiom trans(x:t, y:t, z:t): implies(x == y and y == z, x == z); } Here it is clear: the programmer must define either == or eq or both. If both are defined, the definitions must be equivalent. Failing to define one doesn't cause a compiler error, it causes an infinite loop at run time. Defining both inequivalently doesn't cause an error either, it is just inconsistent. Note the axioms specified constrain the semantics of any definition. Given a definition of == either directly or via a definition of eq, then != is defined automatically, although the programmer might replace the default with something more efficient, clearly such an overspecification has to be consistent. Please note, == could also be defined in terms of !=, but we didn't do that. A characterisation of a partial or total order is more complex. It is much more demanding since there is a combinatorial explosion of possible bases. There is an reason to desire overspecification: performance. There also another reason: choice and convenience. So here, there are several questions: one is how to check semantics are obeyed and I am not looking for an answer here (way too hard!). The other question is: How can we specify, and check, that an instance provides at least a basis? And a much harder question: how can we provide several default definitions which depend on the basis chosen?

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  • Lazy Processing of Streams

    - by Giorgio
    I have the following problem scenario: I have a text file and I have to read it and split it into lines. Some lines might need to be dropped (according to criteria that are not fixed). The lines that are not dropped must be parsed into some predefined records. Records that are not valid must be dropped. Duplicate records may exist and, in such a case, they are consecutive. If duplicate / multiple records exist, only one item should be kept. The remaining records should be grouped according to the value contained in one field; all records belonging to the same group appear one after another (e.g. AAAABBBBCCDEEEFF and so on). The records of each group should be numbered (1, 2, 3, 4, ...). For each group the numbering starts from 1. The records must then be saved somewhere / consumed in the same order as they were produced. I have to implement this in Java or C++. My first idea was to define functions / methods like: One method to get all the lines from the file. One method to filter out the unwanted lines. One method to parse the filtered lines into valid records. One method to remove duplicate records. One method to group records and number them. The problem is that the data I am going to read can be too big and might not fit into main memory: so I cannot just construct all these lists and apply my functions one after the other. On the other hand, I think I do not need to fit all the data in main memory at once because once a record has been consumed all its underlying data (basically the lines of text between the previous record and the current record, and the record itself) can be disposed of. With the little knowledge I have of Haskell I have immediately thought about some kind of lazy evaluation, in which instead of applying functions to lists that have been completely computed, I have different streams of data that are built on top of each other and, at each moment, only the needed portion of each stream is materialized in main memory. But I have to implement this in Java or C++. So my question is which design pattern or other technique can allow me to implement this lazy processing of streams in one of these languages.

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  • How to create Office365 SharePoint site using SharePoint2010 template

    - by ybbest
    Recently, I worked with a client that has office 365 upgraded to SharePoint 2013.But they still like to create the SharePoint site using the old SharePoint2010 template, if you like to know how , here are the steps: 1. Go to your Office 365 portal https://portal.microsoftonline.com/admin/default.aspx and then go to the SharePoint admin page. 2. Next, click settings page. 3. Change the Global experience Version Settings. 4. Finally, you will be able to create SharePoint site using 2010 template.

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  • ASP.NET MVC Tabular Display Template

    The ASP.NET MVC2 templates feature is a pretty nice way to quickly scaffold objects at runtime. Be sure to read Brad Wilsons fantastic series on this topic starting at ASP.NET MVC 2 Templates, Part 1: Introduction. As great as this feature is, there is one template thats conspicuously missing. ASP.NET MVC does not include a template for displaying a list of objects in a tabular format. Earlier today, ScottGu forwarded an email from Daniel Manes (what?! no blog! ;) with a question on how to accomplish...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • T4MVC Add-In to auto run template

    T4MVC is a fantastic solution to avoid 'Magic Strings' in ASP.NET MVC. Thanks to David Ebbo for this contribution which has made its way to MVCContrib. Must keep T4 template open and save it once.This has been the only negative thing about the template. I thought about writing an Add-In for VS to do this and even taked to David about doing it. Well, his latest post has inspired me to...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Marketplace to buy Templates for Twitter Bootstrap framework?

    - by Clay Nichols
    Are there any sites where I could buy a site template designed in Twitter Bootstrap (so that it's easy to modify)? I'm working on a site redesign and I think finding a template that looks close enough and modifying it is an economical way to go. (We're pretty niche so I don't need us to have a super cool website.) But folks I've talked to say that many of those templates are hard to modify. So I'm thinking that finding a template designed in a customizable framework would be easy to modify.

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  • Xcode custom project template creates only references to files

    - by user315374
    Hi, I tried to create a custom project template for setting up unit testing. The problem is that when i create a new project based on this template it creates references to the template files : When i edit a file, it changes my template files instead of my actual project files ! When i delete my template, files from my actual project becomes red ! The project template is in : /Developer/Platforms/iPhoneOS.platform/Developer/Library/Xcode/Project Templates/Application/Test-based Application Reading some question on stack overflow i tried to install my template project in /Library/Application Support/Developer/Shared/Xcode/Project Templates But i cannot see my template when i create a new project. Can anybody help ? Thanks, Vincent

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  • How can I switch timezones in Perl's Template::Plugin::Date?

    - by aidan
    I have a calendar on my website, generated in Perl using Template::Toolkit and Template::Plugin::Date. It highlights the current day. I achieve this by iterating through all the dates (as I print the calendar) and comparing against the current date. Something like this: [% IF cur_date == date.format(format = '%Y-%m-%d') %] ... [% END %] It all works well until someone in Australia looks at it. (They are in a different timezone to me and my server in the UK). What's the best way to get Template::Plugin::Date to use a different time zone? It accepts a 'locale' parameter, but AFAIK this is only used for formatting.

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  • how to use php, html, css togther in a html template [closed]

    - by pandu
    I work with conversion of a html template in to PHP, normally i code like this <div id="test"> <?php echo "<p>hello world</p>"; ?> </div> <?php for($i=0;$i<=8;$i++){ echo "<ul>"; echo "<li>link1"; echo "<li>link2"; echo "</ul>"; } ?> Suggest an easy way to use html tags in php code, other than using a template system, Also tell me how to use for, foreach loop, if else, along with html,CSS tags

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  • Oracle VM RAC template - what it took

    - by wcoekaer
    In my previous posting I introduced the latest Oracle Real Application Cluster / Oracle VM template. I mentioned how easy it is to deploy a complete Oracle RAC cluster with Oracle VM. In fact, you don't need any prior knowledge at all to get a complete production-ready setup going. Here is an example... I built a 4 node RAC cluster, completely configured in just over 40 minutes - starting from import template into Oracle VM, create VMs to fully up and running Oracle RAC. And what was needed? 1 textfile with some hostnames and ip addresses and deploycluster.py. The setup is a 4 node cluster where each VM has 8GB of RAM and 4 vCPUs. The shared ASM storage in this case is 100GB, 5 x 20GB volumes. The VM names are racovm.0-racovm.3. The deploycluster script starts the VMs, verifies the configuration and sends the database cluster configuration info through Oracle VM Manager to the 4 node VMs. Once the VMs are up and running, the first VM starts the actual Oracle RAC setup inside and talks to the 3 other VMs. I did not log into any VM until after everything was completed. In fact, I connected to the database remotely before logging in at all. # ./deploycluster.py -u admin -H localhost --vms racovm.0,racovm.1,racovm.2,racovm.3 --netconfig ./netconfig.ini Oracle RAC OneCommand (v1.1.0) for Oracle VM - deploy cluster - (c) 2011-2012 Oracle Corporation (com: 26700:v1.1.0, lib: 126247:v1.1.0, var: 1100:v1.1.0) - v2.4.3 - wopr8.wimmekes.net (x86_64) Invoked as root at Sat Jun 2 17:31:29 2012 (size: 37500, mtime: Wed May 16 00:13:19 2012) Using: ./deploycluster.py -u admin -H localhost --vms racovm.0,racovm.1,racovm.2,racovm.3 --netconfig ./netconfig.ini INFO: Login password to Oracle VM Manager not supplied on command line or environment (DEPLOYCLUSTER_MGR_PASSWORD), prompting... Password: INFO: Attempting to connect to Oracle VM Manager... INFO: Oracle VM Client (3.1.1.305) protocol (1.8) CONNECTED (tcp) to Oracle VM Manager (3.1.1.336) protocol (1.8) IP (192.168.1.40) UUID (0004fb0000010000cbce8a3181569a3e) INFO: Inspecting /root/rac/deploycluster/netconfig.ini for number of nodes defined... INFO: Detected 4 nodes in: /root/rac/deploycluster/netconfig.ini INFO: Located a total of (4) VMs; 4 VMs with a simple name of: ['racovm.0', 'racovm.1', 'racovm.2', 'racovm.3'] INFO: Verifying all (4) VMs are in Running state INFO: VM with a simple name of "racovm.0" is in a Stopped state, attempting to start it...OK. INFO: VM with a simple name of "racovm.1" is in a Stopped state, attempting to start it...OK. INFO: VM with a simple name of "racovm.2" is in a Stopped state, attempting to start it...OK. INFO: VM with a simple name of "racovm.3" is in a Stopped state, attempting to start it...OK. INFO: Detected that all (4) VMs specified on command have (5) common shared disks between them (ASM_MIN_DISKS=5) INFO: The (4) VMs passed basic sanity checks and in Running state, sending cluster details as follows: netconfig.ini (Network setup): /root/rac/deploycluster/netconfig.ini buildcluster: yes INFO: Starting to send cluster details to all (4) VM(s)....... INFO: Sending to VM with a simple name of "racovm.0".... INFO: Sending to VM with a simple name of "racovm.1"..... INFO: Sending to VM with a simple name of "racovm.2"..... INFO: Sending to VM with a simple name of "racovm.3"...... INFO: Cluster details sent to (4) VMs... Check log (default location /u01/racovm/buildcluster.log) on build VM (racovm.0)... INFO: deploycluster.py completed successfully at 17:32:02 in 33.2 seconds (00m:33s) Logfile at: /root/rac/deploycluster/deploycluster2.log my netconfig.ini # Node specific information NODE1=db11rac1 NODE1VIP=db11rac1-vip NODE1PRIV=db11rac1-priv NODE1IP=192.168.1.56 NODE1VIPIP=192.168.1.65 NODE1PRIVIP=192.168.2.2 NODE2=db11rac2 NODE2VIP=db11rac2-vip NODE2PRIV=db11rac2-priv NODE2IP=192.168.1.58 NODE2VIPIP=192.168.1.66 NODE2PRIVIP=192.168.2.3 NODE3=db11rac3 NODE3VIP=db11rac3-vip NODE3PRIV=db11rac3-priv NODE3IP=192.168.1.173 NODE3VIPIP=192.168.1.174 NODE3PRIVIP=192.168.2.4 NODE4=db11rac4 NODE4VIP=db11rac4-vip NODE4PRIV=db11rac4-priv NODE4IP=192.168.1.175 NODE4VIPIP=192.168.1.176 NODE4PRIVIP=192.168.2.5 # Common data PUBADAP=eth0 PUBMASK=255.255.255.0 PUBGW=192.168.1.1 PRIVADAP=eth1 PRIVMASK=255.255.255.0 RACCLUSTERNAME=raccluster DOMAINNAME=wimmekes.net DNSIP= # Device used to transfer network information to second node # in interview mode NETCONFIG_DEV=/dev/xvdc # 11gR2 specific data SCANNAME=db11vip SCANIP=192.168.1.57 last few lines of the in-VM log file : 2012-06-02 14:01:40:[clusterstate:Time :db11rac1] Completed successfully in 2 seconds (0h:00m:02s) 2012-06-02 14:01:40:[buildcluster:Done :db11rac1] Build 11gR2 RAC Cluster 2012-06-02 14:01:40:[buildcluster:Time :db11rac1] Completed successfully in 1779 seconds (0h:29m:39s) From start_vm to completely configured : 29m:39s. The other 10m was the import template and create 4 VMs from template along with the shared storage configuration. This consists of a complete Oracle 11gR2 RAC database with ASM, CRS and the RDBMS up and running on all 4 nodes. Simply connect and use. Production ready. Oracle on Oracle.

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  • Simple question about a cocos2d based game template

    - by Zishan
    I am learning a cocos2d based Game template tutorial from here and now I am at this point of the tutorial. My question is, how can i run 30 different scenes in 30 different levels of 5 chapter? Now I am using this switch (gameData.selectedLevel) { case 1: [SceneManager goChapter1Level1Scene]; break; (... snip a whole lot of lines...) case 30: [SceneManager goChapter5Level6Scene]; break; default: break; } in the "- (void) onPlay: (CCMenuItemImage*) sender" method. But it work only for 6 levels scene of chapter1. Other 4 chapters levels are show as same as 1st chapter levels scene. they are not show their own level scene. can any one please teach me, how can I do this stuff using this game template?

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  • Using a SQL Prompt snippet with template parameters

    - by SQLDev
    As part of my product management role I regularly attend trade shows and man the Red Gate booth in the vendor exhibition hall. Amongst other things this involves giving product demos to customers. Our latest demo involves SQL Source Control and SQL Test in a continuous integration environment. In order to demonstrate quite how easy it is to set up our tools from scratch we start the demo by creating an entirely new database to link to source control, using an individual database name for each conference attendee. In SQL Server Management Studio this can be done either by selecting New Database from the Object Explorer or by executing “CREATE DATABASE DemoDB_John” in a query window. We recently extended the demo to include SQL Test. This uses an open source SQL Server unit testing framework called tSQLt (www.tsqlt.org), which has a CLR object that requires EXTERNAL_ACCESS to be set as follows: ALTER DATABASE DemoDB_John SET TRUSTWORTHY ON This isn’t hard to do, but if you’re giving demo after demo, this two-step process soon becomes tedious. This is where SQL Prompt snippets come into their own. I can create a snippet named create_demo_db for this following: CREATE DATABASE DemoDB_John GO USE DemoDB_John GO ALTER DATABASE DemoDB_John SET TRUSTWORTHY ON Now I just have to type the first few characters of the snippet name, select the snippet from SQL Prompt’s candidate list, and execute the code. Simple! The problem is that this can only work once due to the hard-coded database name. Luckily I can leverage a nice feature in SQL Server Management Studio called Template Parameters. If I modify my snippet to be: CREATE DATABASE <DBName,, DemoDB_> GO USE <DBName,, DemoDB_> GO ALTER DATABASE <DBName,, DemoDB_> SET TRUSTWORTHY ON Once I’ve invoked the snippet, I can press Ctrl-Shift-M, which calls up the Specify Values for Template Parameters dialog, where I can type in my database name just once. Now you can click OK and run the query. Easy. Ideally I’d like for SQL Prompt to auto-invoke the Template Parameter dialog for all snippets where it detects the angled bracket syntax, but typing in the keyboard shortcut is a small price to pay for the time savings.

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  • Template Matching 2 ROI in a single video capture in real time

    - by YS
    Hi, I am working on a project to perform template matching on a video captured via my webcam. I am able to create 2 template from the webcam capture, but I am unable to perform template matching for both. The program can run only with either template matching, but not both. My program sequence is: Capture from webcam get template 1 get template 2 perform template 1 matching with webcam capture then perform template 2 matching with webcam capture if fail, stop. Can any expert advice me on this?

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  • How can I easily pass all the variables from a template to a partial in Symfony with output escaping

    - by Failpunk
    It there an easy way to pass all the variables a template file has access to onto a partial when I have output escaping on? I tend to create a template file, then refactor things into a partial at some point and it would seem that there would be an easy way to just pass all the same variables from the template to the partial and be done with it. I have output escaping on and I can't just pass in $sf_data. It look like calling a partial from within another partial is very simple...just pass in the variable $vars.

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  • How to define template directives (from an API perspective)?

    - by Ralph
    Preface I'm writing a template language (don't bother trying to talk me out of it), and in it, there are two kinds of user-extensible nodes. TemplateTags and TemplateDirectives. A TemplateTag closely relates to an HTML tag -- it might look something like div(class="green") { "content" } And it'll be rendered as <div class="green">content</div> i.e., it takes a bunch of attributes, plus some content, and spits out some HTML. TemplateDirectives are a little more complicated. They can be things like for loops, ifs, includes, and other such things. They look a lot like a TemplateTag, but they need to be processed differently. For example, @for($i in $items) { div(class="green") { $i } } Would loop over $items and output the content with the variable $i substituted in each time. So.... I'm trying to decide on a way to define these directives now. Template Tags The TemplateTags are pretty easy to write. They look something like this: [TemplateTag] static string div(string content = null, object attrs = null) { return HtmlTag("div", content, attrs); } Where content gets the stuff between the curly braces (pre-rendered if there are variables in it and such), and attrs is either a Dictionary<string,object> of attributes, or an anonymous type used like a dictionary. It just returns the HTML which gets plunked into its place. Simple! You can write tags in basically 1 line. Template Directives The way I've defined them now looks like this: [TemplateDirective] static string @for(string @params, string content) { var tokens = Regex.Split(@params, @"\sin\s").Select(s => s.Trim()).ToArray(); string itemName = tokens[0].Substring(1); string enumName = tokens[1].Substring(1); var enumerable = data[enumName] as IEnumerable; var sb = new StringBuilder(); var template = new Template(content); foreach (var item in enumerable) { var templateVars = new Dictionary<string, object>(data) { { itemName, item } }; sb.Append(template.Render(templateVars)); } return sb.ToString(); } (Working example). Basically, the stuff between the ( and ) is not split into arguments automatically (like the template tags do), and the content isn't pre-rendered either. The reason it isn't pre-rendered is because you might want to add or remove some template variables or something first. In this case, we add the $i variable to the template variables, var templateVars = new Dictionary<string, object>(data) { { itemName, item } }; And then render the content manually, sb.Append(template.Render(templateVars)); Question I'm wondering if this is the best approach to defining custom Template Directives. I want to make it as easy as possible. What if the user doesn't know how to render templates, or doesn't know that he's supposed to? Maybe I should pass in a Template instance pre-filled with the content instead? Or maybe only let him tamper w/ the template variables, and then automatically render the content at the end? OTOH, for things like "if" if the condition fails, then the template wouldn't need to be rendered at all. So there's a lot of flexibility I need to allow in here. Thoughts?

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  • When does a const return type interfere with template instantiation?

    - by Rimo
    From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. ... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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