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  • looping problem while appending data to existing text file

    - by Manu
    try { stmt = conn.createStatement(); stmt1 = conn.createStatement(); stmt2 = conn.createStatement(); rs = stmt.executeQuery("select cust from trip1"); rs1 = stmt1.executeQuery("select cust from trip2"); rs2 = stmt2.executeQuery("select cust from trip3"); File f = new File(strFileGenLoc); OutputStream os = (OutputStream)new FileOutputStream(f,true); String encoding = "UTF8"; OutputStreamWriter osw = new OutputStreamWriter(os, encoding); BufferedWriter bw = new BufferedWriter(osw); } while ( rs.next() ) { while(rs1.next()){ while(rs2.next()){ bw.write(rs.getString(1)==null? "":rs.getString(1)); bw.write("\t"); bw.write(rs1.getString(1)==null? "":rs1.getString(1)); bw.write("\t"); bw.write(rs2.getString(1)==null? "":rs2.getString(1)); bw.write("\t"); bw.newLine(); } } } Above code working fine. My problem is 1. "rs" resultset contains one record in the table 2. "rs1" resultset contains 5 record in the table 3. "rs2" resultset contains 5 record in the table "rs" data is getting recursive. while writing to the same text file , the output i am getting like 1 2 3 1 12 21 1 23 25 1 10 5 1 8 54 but i need output like below 1 2 3 12 21 23 25 10 5 8 54 What things i need to change in my code.. Please advice

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  • Ruby on Rails DataTable now working.

    - by Nimroo
    [Ruby on Rails DataTable guide][1]https://github.com/phronos/rails_datatables/blob/master/README.md I"m following the above and have installed the git plugin as well. All i'm getting is the <%= datatable() % returning " <script type="text/javascript"> $(function() { $('#expenses').dataTable({ "oLanguage": { "sSearch": "Search", "sProcessing": 'Processing' }, "sPaginationType": "full_numbers", "iDisplayLength": 25, "bProcessing": true, "bServerSide": false, "bLengthChange": false, "bStateSave": true, "bFilter": true, "bAutoWidth": true, 'aaSorting': [[0, 'desc']], "aoColumns": [ { 'sType': 'html', 'bSortable':true, 'bSearchable':true ,'sClass':'first' },{ 'sType': 'html', 'bSortable':true, 'bSearchable':true },{ 'sType': 'html', 'bSortable':true, 'bSearchable':true },{ 'sType': 'string', 'bSortable':true, 'bSearchable':true ,'sClass':'last' } ], "fnServerData": function ( sSource, aoData, fnCallback ) { aoData.push( ); $.getJSON( sSource, aoData, function (json) { fnCallback(json); } ); } }); }); </script>". My .html.erb looks like this: <% @page_title="User Page"%> <link rel="stylesheet" href="http://code.jquery.com/ui/1.9.2/themes/base/jquery-ui.css" /> <script src="http://code.jquery.com/jquery-1.8.3.js"></script> <script src="http://code.jquery.com/ui/1.9.2/jquery-ui.js"></script> <%=javascript_include_tag "jquery.dataTables" %> <%=stylesheet_link_tag "jquery-ui-1.9.2.custom" %> <script> $(function() { $( "#tabs" ).tabs(); }); </script> <% if current_user %> <div id="tabs"> <ul> <li><a href="#tabs-1">Expenses</a></li> <li><a href="#tabs-2">Accountant</a></li> <li><a href="#tabs-3">Requests (<%[email protected]%>)</a></li> </ul> <div id="tabs-3"> <p> <% if @requests.count != 0 %> <h2> Accountant Requests </h2> <table > <tr> <thead> <th>First Name</th> <th>Last Name</th> <th>Email Address</th> <th>Accept</th> <th>Reject</th> </thead> </tr> <% @requests.each do |request| %> <tr> <td><%= request.accountant.first_name %></td> <td><%= request.accountant.last_name %></td> <td><%= request.accountant.email %></td> <td><%= link_to 'accept', confirm_accountant_path(:accountant_id => request.accountant_id) %></td> <td><%= link_to 'Edit', edit_expense_path(request) %></td> </tr> <% end %> </tbody> </table> <% else %> <h4> You have no pending requests <h4> <% end %> </p> </div> <div id="tabs-2"> <p> <% if @accountants.count != 0 %> <h2> Accountant Info </h2> <table> <tr> <th>First Name</th> <th>Last Name</th> <th>Email Address</th> </tr> <% @accountants.each do |accountant| %> <tr> <td><%= accountant.first_name %></td> <td><%= accountant.last_name %></td> <td><%= accountant.email %></td> </tr> <% end %> </table> <% else %> <h4> Add Accountant <h4> <p> You don't have an accountant yet, perhaps consider adding one by e-mail </p> <%= render 'add_accountant_form' %> <% end %> <% end %> </p> </div> <div id="tabs-1"> <p><% if current_user %> <h4> Submit new expense </h4> <%= render 'expenses/form' %> <% columns = [{:type => 'html', :class => "first"}, {:type => 'html'}, {:type => 'html'}, {:type => nil, :class => "last"}] %> <%= datatable(columns, {:sort_by => "[0, 'desc']", table_dom_id:"expenses" }) %> <table id="expenses" class="datatable"> <thead> <tr> <th>Entry Date</th> <th>Last Update</th> <th>Amount</th> <th>User</th> <th>Receipt</th> <th></th> <th></th> </tr> </thead> <% @expenses.each do |user_expense| %> <tbody> <tr> <td><%= user_expense.created_at %></td> <td><%= user_expense.updated_at %></td> <td><%= user_expense.amount %></td> <td><%= user_expense.user.username %></td> <% if !user_expense.receipt_img.nil? %> <td><%= image_tag user_expense.receipt_img.url(:thumb) %></td> <% else %> <td>Future Button Here</td> <% end %> <td><%= link_to 'Show', user_expense %></td> <td><%= link_to 'Edit', edit_expense_path(user_expense) %></td> </tr> </tbody> <% end %> </table> <% end %></p> </div> </div>

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  • How do I optimize this postfix expression tree for speed?

    - by Peter Stewart
    Thanks to the help I received in this post: I have a nice, concise recursive function to traverse a tree in postfix order: deque <char*> d; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } d.push_front(cargo); return; }; This is an expression tree. The branch nodes are operators randomly selected from an array, and the leaf nodes are values or the variable 'x', also randomly selected from an array. char *values[10]={"1.0","2.0","3.0","4.0","5.0","6.0","7.0","8.0","9.0","x"}; char *ops[4]={"+","-","*","/"}; As this will be called billions of times during a run of the genetic algorithm of which it is a part, I'd like to optimize it for speed. I have a number of questions on this topic which I will ask in separate postings. The first is: how can I get access to each 'cargo' as it is found. That is: instead of pushing 'cargo' onto a deque, and then processing the deque to get the value, I'd like to start processing it right away. I don't yet know about parallel processing in c++, but this would ideally be done concurrently on two different processors. In python, I'd make the function a generator and access succeeding 'cargo's using .next(). But I'm using c++ to speed up the python implementation. I'm thinking that this kind of tree has been around for a long time, and somebody has probably optimized it already. Any Ideas? Thanks

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  • Creating a three level ASP.NET menu with SiteMap, how do i do it?

    - by user270399
    I want to create a three level menu, I have got a recursive function today that works with three levels. But the thing is how do i output the third lever? Using two repeaters i have managed to get a hold of the first two levels through the ChildNodes property. But that only gives me the second level. What if a want the third level? Example code below. How do i get the third level? :) <asp:Repeater ID="FirstLevel" DataSourceID="SiteMapDataSource" runat="server" EnableViewState="false"> <ItemTemplate> <li class="top"> <a href='/About/<%#Eval("Title")%>.aspx' class="top_link"><span class="down"><%#Eval("Title")%></span><!--[if gte IE 7]><!--></a><!--<![endif]--> <asp:Repeater runat="server" ID="SecondLevel" DataSource='<%#((SiteMapNode)Container.DataItem).ChildNodes%>'> <HeaderTemplate><!--[if lte IE 6]><table><tr><td><![endif]--><ul class="sub"></HeaderTemplate> <ItemTemplate> <li> <a href='<%#((string)Eval("Url")).Replace("~", "")%>' style="text-align: left;"><%#Eval("Title")%></a> Third repeater here? </li> </ItemTemplate> <FooterTemplate></ul><!--[if lte IE 6]></td></tr></table></a><![endif]--></FooterTemplate> </asp:Repeater> </li> </ItemTemplate> </asp:Repeater>

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  • Recursion in assembly?

    - by Davis
    I'm trying to get a better grasp of assembly, and I am a little confused about how to recursively call functions when I have to deal with registers, popping/pushing, etc. I am embedding x86 assembly in C++. Here I am trying to make a method which given an array of integers will build a linked list containing these integers in the order they appear in the array. I am doing this by calling a recursive function: insertElem (struct elem *head, struct elem *newElem, int data) -head: head of the list -data: the number that will be inserted at the end of a list -newElem: points to the location in memory where I will store the new element (data field) My problem is that I keep overwriting the registers instead of a typical linked list. For example, if I give it an array {2,3,1,8,3,9} my linked-list will return the first element (head) and only the last element, because the elements keep overwriting each other after head is no longer null. So here my linked list looks something like: 2--9 instead of 2--3--1--8--3--9 I feel like I don't have a grasp on how to organize and handle the registers. newElem is in EBX and just keeps getting rewritten. Thanks in advance!

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  • How to get the size of a binary tree ?

    - by Andrei Ciobanu
    I have a very simple binary tree structure, something like: struct nmbintree_s { unsigned int size; int (*cmp)(const void *e1, const void *e2); void (*destructor)(void *data); nmbintree_node *root; }; struct nmbintree_node_s { void *data; struct nmbintree_node_s *right; struct nmbintree_node_s *left; }; Sometimes i need to extract a 'tree' from another and i need to get the size to the 'extracted tree' in order to update the size of the initial 'tree' . I was thinking on two approaches: 1) Using a recursive function, something like: unsigned int nmbintree_size(struct nmbintree_node* node) { if (node==NULL) { return(0); } return( nmbintree_size(node->left) + nmbintree_size(node->right) + 1 ); } 2) A preorder / inorder / postorder traversal done in an iterative way (using stack / queue) + counting the nodes. What approach do you think is more 'memory failure proof' / performant ? Any other suggestions / tips ? NOTE: I am probably going to use this implementation in the future for small projects of mine. So I don't want to unexpectedly fail :).

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  • caching previous return values of procedures in scheme

    - by Brock
    In Chapter 16 of "The Seasoned Schemer", the authors define a recursive procedure "depth", which returns 'pizza nested in n lists, e.g (depth 3) is (((pizza))). They then improve it as "depthM", which caches its return values using set! in the lists Ns and Rs, which together form a lookup-table, so you don't have to recurse all the way down if you reach a return value you've seen before. E.g. If I've already computed (depthM 8), when I later compute (depthM 9), I just lookup the return value of (depthM 8) and cons it onto null, instead of recursing all the way down to (depthM 0). But then they move the Ns and Rs inside the procedure, and initialize them to null with "let". Why doesn't this completely defeat the point of caching the return values? From a bit of experimentation, it appears that the Ns and Rs are being reinitialized on every call to "depthM". Am I misunderstanding their point? I guess my question is really this: Is there a way in Scheme to have lexically-scoped variables preserve their values in between calls to a procedure, like you can do in Perl 5.10 with "state" variables?

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  • breadth-first traversal of directory tree is not lazy

    - by user855443
    I try to traverse the diretory tree. A naive depth-first traversal seems not to produce the data in a lazy fashion and runs out of memory. I next tried a breadth first approach, which shows the same problem - it uses all the memory available and then crashes. the code i have is: getFilePathBreadtFirst :: FilePath -> IO [FilePath] getFilePathBreadtFirst fp = do fileinfo <- getInfo fp res :: [FilePath] <- if isReadableDirectory fileinfo then do children <- getChildren fp lower <- mapM getFilePathBreadtFirst children return (children ++ concat lower) return (children ++ concat () else return [fp] -- should only return the files? return res getChildren :: FilePath -> IO [FilePath] getChildren path = do names <- getUsefulContents path let namesfull = map (path </>) names return namesfull testBF fn = do -- crashes for /home/frank, does not go to swap fps <- getFilePathBreadtFirst fn putStrLn $ unlines fps I think all the code is either linear or tail recursive, and I would expect that the listing of filenames starts immediately, but in fact it does not. Where is the error in my code and my thinking? where have I lost lazy evaluation?

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  • Communication between lexer and parser

    - by FredOverflow
    Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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  • Find all ways to insert zeroes into a bit pattern

    - by James
    I've been struggling to wrap my head around this for some reason. I have 15 bits that represent a number. The bits must match a pattern. The pattern is defined in the way the bits start out: they are in the most flush-right representation of that pattern. So say the pattern is 1 4 1. The bits will be: 000000010111101 So the general rule is, take each number in the pattern, create that many bits (1, 4 or 1 in this case) and then have at least one space separating them. So if it's 1 2 6 1 (it will be random): 001011011111101 Starting with the flush-right version, I want to generate every single possible number that meets that pattern. The # of bits will be stored in a variable. So for a simple case, assume it's 5 bits and the initial bit pattern is: 00101. I want to generate: 00101 01001 01010 10001 10010 10100 I'm trying to do this in Objective-C, but anything resembling C would be fine. I just can't seem to come up with a good recursive algorithm for this. It makes sense in the above example, but when I start getting into 12431 and having to keep track of everything it breaks down.

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  • C++. How to define template parameter of type T for class A when class T needs a type A template parameter?

    - by jaybny
    Executor class has template of type P and it takes a P object in constructor. Algo class has a template E and also has a static variable of type E. Processor class has template T and a collection of Ts. Question how can I define Executor< Processor<Algo> > and Algo<Executor> ? Is this possible? I see no way to defining this, its kind of an "infinite recursive template argument" See code. template <class T> class Processor { map<string,T> ts; void Process(string str, int i) { ts[str].Do(i); } } template <class P> class Executor { Proc &p; Executor(P &p) : Proc(p) {} void Foo(string str, int i) { p.Process(str,i); } Execute(string str) { } } template <class E> class Algo { static E e; void Do(int i) {} void Foo() { e.Execute("xxx"); } } main () { typedef Processor<Algo> PALGO; // invalid typedef Executor<PALGO> EPALGO; typedef Algo<EPALGO> AEPALGO; Executor<PALGO> executor(PALGO()); AEPALGO::E = executor; }

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  • Aggregate path counts using HierarchyID

    - by austincav
    Business problem - understand process fallout using analytics data. Here is what we have done so far: Build a dictionary table with every possible process step Find each process "start" Find the last step for each start Join dictionary table to last step to find path to final step In the final report output we end up with a list of paths for each start to each final step: User Fallout Step HierarchyID.ToString() A 1/1/1 B 1/1/1/1/1 C 1/1/1/1 D 1/1/1 E 1/1 What this means is that five users (A-E) started the process. Assume only User B finished, the other four did not. Since this is a simple example (without branching) we want the output to look as follows: Step Unique Users 1 5 2 5 3 4 4 2 5 1 The easiest solution I could think of is to take each hierarchyID.ToString(), parse that out into a set of subpaths, JOIN back to the dictionary table, and output using GROUP BY. Given the volume of data, I'd like to use the built-in HierarchyID functions, e.g. IsAncestorOf. Any ideas or thoughts how I could write this? Maybe a recursive CTE?

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  • Best implementation of Java Queue?

    - by Georges Oates Larsen
    I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

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  • Hide/Show some HTML table cells individually and align the remaining cells as they belong to the same row [closed]

    - by Brian
    [Edited at the resquest of admins] The best way I can explain my problem is showning an example. I have the table that you can see on the link below (since I can't post images...), that ha a table head (blue) and four rows, whose cells are green and white in color. I just want the white cells to hide/show alternately by clicking on green cells, which would remain always visible as parent cells. After hiding white cells, the green ones should be aligned into the same row, as they would fit like tetris bricks. That's all, I think more clear is impossible. http://i.stack.imgur.com/3n3In.jpg (follow the link to see the image explanation) The table code: <table class="columns" cellspacing="0" border="0"> <tr> <td class="left" rowspan="2"> <div style="text-align:center;"></div> </td> </tr><tr><td class="middle"> <div id="detail_table_source" style="display:none"></div> <br> <table id="detail_table" class="detail"> <colgroup> <col style="width:20px;"> <col style="width:40px;"> <col style="width:70px;"> <col style="width:20px;"> </colgroup> <thead> <tr> <th width="88">Blahhh</th> <th width="211">BLAHH</th> <th width="229">BLAHH</th> </tr> </thead> <tbody> <tr class="parent" id="row123" style="cursor: pointer; " title="Click to expand/collapse"> <td bgcolor="#A6A4CC">Blahhh</td> <td bgcolor="#A6A4CC">blah blah </td> <td bgcolor="#A6A4CC">Blahh</td> </tr> <tr class="child-row123" style="display: none; "> <td rowspan="3" bgcolor="#5B5B5B">&nbsp;</td> <td>blah blah </td> <td>blah blah</td> </tr> <tr class="child-row123" style="display: none; "> <td>blah blah</td> <td>blah blah</td> </tr> <tr class="child-row123" style="display: none; "> <td>blah blah</td> <td>blah blah</td> </tr> <tr> <td bgcolor="#6B7A94" class="parent" id="row456" style="cursor: pointer; " title="Click to expand/collapse"><strong>Blahh</strong></td> <td bgcolor="#FFFFFF" class="child-cell456" style="display: none; ">blah blah</td> <td bgcolor="#FFFFFF" class="child-cell456" style="display: none; ">blah blah</td> </tr> <tr> <td rowspan="4" valign="top" bgcolor="#5B5B5B" class="child-row456" style="display: none; ">&nbsp;</td> <td bgcolor="#6B7A94" class="parent" id="cell456" style="cursor: pointer; " title="Click to expand/collapse">blah blah</td> <td bgcolor="#6B7A94" class="parent" id="cell456" style="cursor: pointer; " title="Click to expand/collapse">blah blah</td> </tr> <tr> <td class="child-cell456" style="display: none; ">blah blah</td> <td class="child-cell456" style="display: none; ">blah blah</td> </tr> <tr> <td class="child-cell456" style="display: none; ">blah blah</td> <td class="child-cell456" style="display: none; ">blah blah</td> </tr> </tbody> </table> The script to hide/show whole rows (this works because it is copied from another example): <script language="javascript"> $(function() { $('tr.parent') .css("cursor","pointer") .attr("title","Click to expand/collapse") .click(function(){ $(this).siblings('.child-'+this.id).toggle(); }); $('tr[@class^=child-]').hide().children('td'); }); </script> And the failed attempt at expanding/hiding individual cells: <script language="javascript"> $(function() { $('td.parent') .css("cursor","pointer") .attr("title","Click to expand/collapse") .click(function(){ $(this).siblings('.child-'+this.id).toggle(); }); $('td[@class^=child-]').hide().children('td'); }); </script>

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  • Stretch UL to fill the entire DIV

    - by Interfaith
    There is a similar post: Stretch horizontal ul to fit width of div But mine is a little bit tricky, as I have tried the above example but failed. My code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-… <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title></title> <script type='text/javascript' src='https://ajax.googleapis.com/ajax/li… <script> function mainmenu(){ $(" #nav ul ").css({display: "none"}); // Opera Fix $(" #nav li").hover(function(){ $(this).find('ul:first').css({visibi… "visible",display: "none"}).show(400); },function(){ $(this).find('ul:first').css({visibi… "hidden"}); }); } $(document).ready(function(){ mainmenu(); }); </script> <style> body{ font-size:0.85em; font-family:Verdana, Arial, Helvetica, sans-serif; } #nav, #nav ul{ margin:0; padding:0; list-style-type:none; list-style-position:outside; position:relative; line-height:1.5em; display: table; width: 100%; } #nav a{ display:block; padding:10px 15px 10px 15px; border:1px solid #fff; color:#fff; text-align: center; margin:0; text-decoration:none; background: #C34328; border-top:1px solid #EF593B; -moz-box-shadow:0px 3px 4px #591E12 inset; -webkit-box-shadow:0px 3px 4px #591E12 inset; -box-shadow:0px 3px 4px #591E12 inset; } #nav a:hover{ background-color:#fff; color:#333; } #nav li{ float:left; position:relative; } #nav ul { position:absolute; display:none; width:12em; top:3.2em; } #nav li ul a{ width:12em; height:auto; float:left; } #nav ul ul{ top:auto; } #nav li ul ul { left:12em; margin:0px 0 0 10px; } </style> </head> <body> <div style="width: 980px; border: 1px black solid;"> <ul id="nav"> <li><a href="#">Find a Doctor</a></li> <li><a href="#">Why Interfaith</a></li> <li><a href="#">For Patients & Visitors</a> <ul> <li><a href="#">3.1 jQuery</a></li> <li><a href="#">3.2 Mootools</a></li> <li><a href="#">3.3 Prototype</a></li> </ul> </li> <li><a href="#">Medical Services</a> <ul> <li><a href="#">Behavioral Health</a></li> <li><a href="#">Clinical Laboratory</a></li> <li><a href="#">Dentistry</a></li> <li><a href="#">Emergency</a></li> <li><a href="#">Gynecology</a></li> <li><a href="#">Medicine</a></li> <li><a href="#">Pastoral</a></li> <li><a href="#">Pediatrics</a></li> <li><a href="#">Physical Medicine & Rehab</a></li> </ul> </li> <li><a href="#">Medical Trainings</a> <ul> <li><a href="#">Medical Training</a></li> <li><a href="#">Behavioral Health</a></li> <li><a href="#">Predoctoral Externship</a></li> <li><a href="#">Podiatric Residency</a></li> <li><a href="#">Dental Residency</a></li> <li><a href="#">Pulmonary Medicine</a></li> </ul> </li> <li><a href="#">Contact</a></li> </ul> </div> </body> </html> Can someone tell me where I have to edit to complete the code? Thanks

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  • Best Functional Approach

    - by dbyrne
    I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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  • Pascals Triangle by recursion

    - by Olpers
    Note : My Class Teacher gave me this question as an assignment... I am not asked to do it but please tell me how to do it with recursion Binomial coefficients can be calculated using Pascal's triangle: 1 n = 0 1 1 1 2 1 1 3 3 1 1 4 6 4 1 n = 4 Each new level of the triangle has 1's on the ends; the interior numbers are the sums of the two numbers above them. Task: Write a program that includes a recursive function to produce a list of binomial coefficients for the power n using the Pascal's triangle technique. For example, Input = 2 Output = 1 2 1 Input = 4 Output = 1 4 6 4 1 done this So Far but tell me how to do this with recursion... #include<stdio.h> int main() { int length,i,j,k; //Accepting length from user printf("Enter the length of pascal's triangle : "); scanf("%d",&length); //Printing the pascal's triangle for(i=1;i<=length;i++) { for(j=1;j<=length-i;j++) printf(" "); for(k=1;k<i;k++) printf("%d",k); for(k=i;k>=1;k--) printf("%d",k); printf("\n"); } return 0; }

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  • How to write a simple Lexer/Parser with antlr 2.7?

    - by Burkhard
    Hello, I have a complex grammar (in antlr 2.7) which I need to extend. Having never used antlr before, I wanted to write a very simple Lexer and Parser first. I found a very good explanation for antlr3 and tried to adapt it: header{ #include <iostream> using namespace std; } options { language="Cpp"; } class P2 extends Parser; /* This will be the entry point of our parser. */ eval : additionExp ; /* Addition and subtraction have the lowest precedence. */ additionExp : multiplyExp ( "+" multiplyExp | "-" multiplyExp )* ; /* Multiplication and addition have a higher precedence. */ multiplyExp : atomExp ( "*" atomExp | "/" atomExp )* ; /* An expression atom is the smallest part of an expression: a number. Or when we encounter parenthesis, we're making a recursive call back to the rule 'additionExp'. As you can see, an 'atomExp' has the highest precedence. */ atomExp : Number | "(" additionExp ")" ; /* A number: can be an integer value, or a decimal value */ number : ("0".."9")+ ("." ("0".."9")+)? ; /* We're going to ignore all white space characters */ protected ws : (" " | "\t" | "\r" | "\n") { newline(); } ; It does generate four files without errors: P2.cpp, P2.hpp, P2TokenTypes.hpp and P2TokenTypes.txt. But now what? How do I create a working programm with that? I tried to add these files to a VS2005-WinConsole-Project but it does not compile: p2.cpp(277) : fatal error C1010: unexpected end of file while looking for precompiled header. Did you forget to add '#include "stdafx.h"' to your source?

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  • How to transform a production to LL(1) grammar for a list separated by a semicolon?

    - by Subb
    Hi, I'm reading this introductory book on parsing (which is pretty good btw) and one of the exercice is to "build a parser for your favorite language." Since I don't want to die today, I thought I could do a parser for something relatively simple, ie a simplified CSS. Note: This book teach you how to right a LL(1) parser using the recursive-descent algorithm. So, as a sub-exercice, I am building the grammar from what I know of CSS. But I'm stuck on a production that I can't transform in LL(1) : //EBNF block = "{", declaration, {";", declaration}, [";"], "}" //BNF <block> =:: "{" <declaration> "}" <declaration> =:: <single-declaration> <opt-end> | <single-declaration> ";" <declaration> <opt-end> =:: "" | ";" This describe a CSS block. Valid block can have the form : { property : value } { property : value; } { property : value; property : value } { property : value; property : value; } ... The problem is with the optional ";" at the end, because it overlap with the starting character of {";", declaration}, so when my parser meet a semicolon in this context, it doesn't know what to do. The book talk about this problem, but in its example, the semicolon is obligatory, so the rule can be modified like this : block = "{", declaration, ";", {declaration, ";"}, "}" So, Is it possible to achieve what I'm trying to do using a LL(1) parser?

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  • Scheme: Mysterious void in pattern match.

    - by Schemer
    Hi. I am writing a function called annotate that uses match-lambda -- often with recursive calls to annotate. Here is one of the pattern matches: (`(lambda (,<param1> . ,<params>) ,<stmts>) `(CLOSURE ENV (,<param1> . ,<params>) (lambda (ENV) ,(map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))))) However, when this pattern is matched this is what returns: '(CLOSURE ENV (x) (lambda (ENV) ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y)))))) #<void>) Specifically I can't figure out where "void" is coming from. In fact, if I include the line: ,(displayln (map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))) it prints: ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y))))) notably without "void". If someone could tell me what the problem is it would be greatly appreciated. Thanks.

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  • How to handle build rule with unknown targets in OMake when target list generator is built

    - by Michael E
    I have a project which uses OMake for its build system, and I am trying to handle a rather tough corner case. I have some definition files and a tool which can take these definition files and create GraphViz files. There are two problems, though: Each definition file can produce multiple graphs, and the list of graphs it can produce is encoded in the file. My dump tool does have a -list option which lists all the graphs a definition file will produce. This dump tool is built in the source tree. I want this list available in the OMakefile so I can use other rules to convert the DOT files to SVG, and have a phony target depend on all the SVGs (goal: a single build command which builds SVG descriptions of all my graphs). If I only had the first problem, it would be easy - I would run the tool to build a list, and then use that list to build a target which invokes the dumper to output the GraphViz files. However, I am rather stuck on forcing the dump tool to be built before it is needed. If this were make, I would just run make recursively to build the dump tool. OMake does not allow recursive invocation, however, and the build function is only usable from osh. Any suggestions for a good solution to this problem?

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  • TortoiseSVN Error: "OPTIONS of 'https://...' could not connect to server (...)"

    - by Zack Peterson
    I'm trying to setup a new computer to synchronize with my SVN repository that's hosted with cvsdude.com. I get this error: Here's what I did (these have worked in the past): Downloaded and installed TortoiseSVN Created a new folder C:\aspwebsite Right-clicked, chose SVN Checkout... Entered the following information, clicked OK: URL of repository: https://<reponame>-svn.cvsdude.com/aspwebsite Checkout directory: C:\aspwebsite Checkout depth: Fully recursive Omit externals: Unchecked Revision: HEAD revision Got TortoiseSVN error: OPTIONS of 'https://<reponame>-svn.cvsdude.com/aspwebsite': could not connect to server (https://<reponame>-svn.cvsdude.com) Rather than getting the error, TortoiseSVN should have asked for my username and password and then downloaded about 90MB. Why can't I checkout from my Subversion repository? Kent Fredric wrote: Either their security certificate has expired, or their hosting is broken/down. Contact CVSDude and ask them whats up. It could also be a timeout, because for me their site is exhaustively slow.. It errors after only a couple seconds. I don't think it's a timeout. Matt wrote: Try visiting https://[redacted]-svn.cvsdude.com/aspwebsite and see what happens. If you can visit it in your browser, you ought to be able to get the files in your SVN client and we can work from there. If it fails, then there's your answer. I can access the site in a web browser.

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  • Has anyone ever had OpenCV work with Python 2.7 on MacOS 10.6?

    - by ?????
    I've been trying on and off for the past 6 months to get OpenCV to work with Python on MacOS. Every time there's a new release, I try again and fail. I've tried both 64-bit and 32-bit, and both the xcode gcc and gcc installed via macports. I just spend the past two days on it, hopeful that the latest OpenCV release, that appears to include Python support directly would work. It doesn't. I've also tried and failed to use this: http://code.google.com/p/pyopencv/ I've been using OpenCV with C++ or Microsoft C++/CLI for the past few years, but I'd love to use it with Python on a Mac because that is my primary development environment. I'd love to hear from anyone who's actually been able to get the opencv python examples to run under Mac OS 10.6, either 32 or 64-bit. My last attempt was to follow the instructions on this page http://recursive-design.com/blog/2010/12/14/face-detection-with-osx-and-python/ with a clean, fresh install of 10.6 on a 64-bit capable Mac. My PYTHONPATH is set, and I can see the cv library in it. But an "import cv" from python fails. Previously, the closest I've ever gotten (again, staring on a clean, fresh 10.6 install) was this: Python 2.7.1 (r271:86882M, Nov 30 2010, 10:35:34) [GCC 4.2.1 (Apple Inc. build 5664)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import cv Fatal Python error: Interpreter not initialized (version mismatch?) Abort trap thrilllap-2:~ swirsky$ I've seen a lot of folks answering similar questions here, but have never seen an definitive answer for it.

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  • PHP: Three item validation comparison

    - by DavidYell
    I have 3 featured product panels on the homepage, and I'm writing a CMS page for it. I'm trying to validate the items. They are selected via three <select> elements, featured1, featured2 and featured3. The default is <option value="0" selected>Select an element</option> I need to validate the $_POST to ensure that the user hasn't selected the same product for more than one of the panels. I have worked out that each $_POST needs to be $_POST['featuredN'] > 0 but I can't seem to find a logical way of processing the 7 potential outcomes. Using a logic table, where 1 is a set value. 1 2 3 ------- 0 0 0 1 1 1 1 0 0 0 1 0 0 0 1 1 1 0 0 1 1 If an item is 0, then I will not update it, but I want the user to be able to update a single item if needs be. I cannot find a logical way to see if the item is not 0, and then compare it to another item if that also is not 0. So far my colleague suggested, adding up the values. Which works to see if condition 1 0 0 0 is not met. I have a vague feeling that some form of recursive function might be in order, but I can't quite get my brain to help me on this one! So to the collective brain! :)

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  • Mixing together Connect by, inner join and sum with Oracle

    - by François
    Hey there, I need help with a oracle query. Excuse me in advance for my english. Here is my setup: I have 2 tables called respectively "tasks" and "timesheets". The "tasks" table is a recursive one, that way each task can have multiple subtasks. Each timesheet is associated with a task (not necessarily the "root" task) and contains the number of hours worked on it. Example: Tasks id:1 | name: Task A | parent_id: NULL id:2 | name: Task A1 | parent_id: 1 id:3 | name: Task A1.1 | parent_id: 2 id:4 | name: Task B | parent_id: NULL id:5 | name: Task B1 | parent_id: 4 Timesheets id:1 | task_id: 1 | hours: 1 id:2 | task_id: 2 | hours: 3 id:3 | task_id:3 | hours: 1 id:5 | task_id:5 | hours:1 ... What I want to do: I want a query that will return the sum of all the hours worked on a "task hierarchy". If we take a look at the previous example, It means I would like to have the following results: task A - 5 hour(s) | task B - 1 hour(s) At first I tried this SELECT TaskName, Sum(Hours) "TotalHours" FROM ( SELECT replace(sys_connect_by_path(decode(level, 1, t.name), '~'), '~') As TaskName, ts.hours as hours FROM tasks t INNER JOIN timesheets ts ON t.id=ts.task_id START WITH PARENTOID=-1 CONNECT BY PRIOR t.id = t.parent_id ) GROUP BY TaskName Having Sum(Hours) > 0 ORDER BY TaskName And it almost work. THe only problem is that if there are no timesheet for a root task, it will skip the whole hieararchy... but there might be timesheets for the child rows and it is exactly what happens with Task B1. I know it is the "inner join" part that is causing my problem but I'm not sure how can I get rid of it. Any idea how to solve this problem? Thank you

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