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• Mis-spelling in the .NET configuration system, a design flaw?

  - by smwikipedia

  I just wrote some .NET code to get connection string from the config file. The config file is as below: <?xml version="1.0" encoding="utf-8" ?> <configuration> <appSettings> <add key="key1" value="hello,world!"/> </appSettings> <connectionStrings> <add name="conn1" connectionString="abcd"/> </connectionStrings> </configuration> .NET Framework provide the following types to get the connection string: 1- ConnectionStringsSection : stands for the config section containing several connection strings 2- ConnectionStringSettingsCollection : stands for the connection string collection 3- ConnectionStringSettings : stands for a certain connection string. .NET Framework also provide the following types to get the App Settings: 4- AppSettingsSection 5- KeyValueConfigurationCollection 6- KeyValueConfigurationElement Compare 2 to 5, 3 to 6, why are there extra "s" in ConnectionStringSetting[s]Collection and ConnectionStringSetting[s]? This mis-spelling is really mis-leading. I think it's a design flaw. Has anyone noticed that?

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• How could I eliminate the meter names with an 'x' after them?

  - by Rose Comete

  Hi I imported some Excel data into MatLab - it is a list of about 200 meter names with about 28 rows each, but the problem is that for each there is a duplicate for the other direction - with the same meter name with an 'x' after it. Does anyone have any ideas as to how I can eliminate these ones with an 'x' after wards? Attached is the part of my code that imports the data, but unfortunately I have not got enough points on this site yet to be allowed to upload data/photos x clear all fid=fopen('sue1.csv'); % Open the file sue1.csv and read it all and put it into an array data = textscan(fid,'%s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s','Delimiter',',','CollectOutput',1); fclose(fid) j = 1; k = 1; % j - turbine number, k - date number for i = 1:length(data{1,1}) % Run through all the data if strcmp(data{1,1}(i),'') == 0 meterold{j}(k,:) = data{1,1}(i,:); % if strcmp(data{1,1}(i),'MeterName') == 0 % nummeter{j}(k,:) = str2num(data{1,1}(i,3:end)); % end k = k + 1; else % These commands are followed in the strings match (empty line) k = 1; % Reset the day counter as we're back to the beginning j = j + 1; % Add one to the meter counter as we're now looking at % a new turbine end end

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• Getting dialogue snippets from text using regular expressions

  - by sheldon

  I'm trying to extract snippets of dialogue from a book text. For example, if I have the string "What's the matter with the flag?" inquired Captain MacWhirr. "Seems all right to me." Then I want to extract "What's the matter with the flag?" and "Seem's all right to me.". I found a regular expression to use here, which is "[^"\\]*(\\.[^"\\]*)*". This works great in Eclipse when I'm doing a Ctrl+F find regex on my book .txt file, but when I run the following code: String regex = "\"[^\"\\\\]*(\\\\.[^\"\\\\]*)*\""; String bookText = "\"What's the matter with the flag?\" inquired Captain MacWhirr. \"Seems all right to me.\""; Pattern p = Pattern.compile(regex); Matcher m = p.matcher(bookText); if(m.find()) System.out.println(m.group(1)); The only thing that prints is null. So am I not converting the regex into a Java string properly? Do I need to take into account the fact that Java Strings have a \" for the double quotes?

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• How to deal with unknown entity references?

  - by Chris

  I'm parsing (a lot of) XML files that contain entity references which i dont know in advance (can't change that fact). For example: xml = "<tag>I'm content with &funny; &entity; &references;.</tag>" when i try to parse this using the following code: final DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); final DocumentBuilder db = dbf.newDocumentBuilder(); final InputSource is = new InputSource(new StringReader(xml)); final Document d = db.parse(is); i get the following exception: org.xml.sax.SAXParseException: The entity "funny" was referenced, but not declared. but, what i do want to achieve is, that the parser replaces every entity that is not declared (unknown to the parser) with an empty String ''. Or even better, is there a way to pass a map to the parser like: Map<String,String> entityMapping = ... entityMapping.put("funny","very"); entityMapping.put("entity","important"); entityMapping.put("references","stuff"); so that i could do the following: final DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); final DocumentBuilder db = dbf.newDocumentBuilder(); final InputSource is = new InputSource(new StringReader(xml)); db.setEntityResolver(entityMapping); final Document d = db.parse(is); if i would obtain the text from the document using this example code i should receive: I'm content with very important stuff. Any suggestions? Of course, i already would be happy to just replace the unknown entity's with empty strings. Thanks,

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• RIA Service - without database?

  - by Heko

  Helo! I need to write a RIA service to call Java webservices from Silverlight 3.0 app. I'm testing how stuff works and in my Web app I have a MyData class which has 2 properties (int ID, string Text): namespace SilverlightApplication1.Web { public class MyData { [Key] public int ID { get; set; } public string Text { get; set; } } } Then I wrote simple DomainService: [EnableClientAccess()] public class MyService : DomainService { public IQueryable<MyData> GetMyData(string Url) { // here I will call my WebService List<MyData> result = new List<MyData>(); result.Add(new MyData { ID = 1, Text = Url }); return result.AsQueryable(); } } } How can I get data into my SL app? Now I have this: namespace SilverlightApplication1 { public partial class MainPage : UserControl { public MainPage() { InitializeComponent(); MyContext context = new MyContext(); } } } I called and load but nothink worsk (exceptions, or nulls)... I had Invoke annotation but MyData is not TEntity and I can't use Strings or other simple types as well... :/ I'm reading and reading posts and nothing works like it should.. Any help would be really appreciated. Thank you!

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• Why doesn't String's hashCode() cache 0?

  - by polygenelubricants

  I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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• Ruby integer to string key

  - by Gene

  A system I'm building needs to convert non-negative Ruby integers into shortest-possible UTF-8 string values. The only requirement on the strings is that their lexicographic order be identical to the natural order on integers. What's the best Ruby way to do this? We can assume the integers are 32 bits and the sign bit is 0. This is successful: (i >> 24).chr + ((i >> 16) & 0xff).chr + ((i >> 8) & 0xff).chr + (i & 0xff).chr But it appears to be 1) garbage-intense and 2) ugly. I've also looked at pack solutions, but these don't seem portable due to byte order. FWIW, the application is Redis hash field names. Building keys may be a performance bottleneck, but probably not. This question is mostly about the "Ruby way".

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• Member function overloading/template specialization issue

  - by Ferruccio

  I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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• pointer, malloc and char in C

  - by user2534078

  im trying to copy a const char array to some place in the memory and point to it . lets say im defining this var under the main prog : char *p = NULL; and sending it to a function with a string : myFunc(&p, "Hello"); now i want that at the end of this function the pointer will point to the letter H but if i puts() it, it will print Hello . here is what i tried to do : void myFunc(char** ptr , const char strng[] ) { *ptr=(char *) malloc(sizeof(strng)); char * tmp=*ptr; int i=0; while (1) { *ptr[i]=strng[i]; if (strng[i]=='\0') break; i++; } *ptr=tmp; } i know its a rubbish now, but i would like to understand how to do it right, my idea was to allocate the needed memory, copy a char and move forward with the pointer, etc.. also i tried to make the ptr argument byreferenec (like &ptr) but with no success due to a problem with the lvalue and rvalue . the only thing is changeable for me is the function, and i would like not to use strings, but chars as this is and exercise . thanks for any help in advance.

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• Passing mix of T and T[] to a Java varargs method

  - by rfalke

  Suppose you have a Java method void foobar(int id, String ... args) and want to pass both String arrays and Strings into the method. Like this String arr1[]={"adas", "adasda"}; String arr2[]={"adas", "adasda"}; foobar(0, "adsa", "asdas"); foobar(1, arr1); foobar(2, arr1, arr2); foobar(3, arr1, "asdas", arr2); In Python there is "*" for this. Is there some way better than such rather ugly helper method: static String[] concat(Object... args) { List<String> result = new ArrayList<String>(); for (Object arg : args) { if (arg instanceof String) { String s = (String) arg; result.add(s); } else if (arg.getClass().isArray() && arg.getClass().getComponentType().equals(String.class)) { String arr[] = (String[]) arg; for (String s : arr) { result.add(s); } } else { throw new RuntimeException(); } } return result.toArray(new String[result.size()]); } which allows foobar(4, concat(arr1, "asdas", arr2));

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• How do I fix the alpha value after calling GDI text functions?

  - by Daniel Stutzbach

  I have a application that uses the Aero glass effect, so each pixel has an alpha value in addition to red, green, and blue values. I have one custom-draw control that has a solid white background (alpha = 255). I would like to draw solid text on the control using the GDI text functions. However, these functions set the alpha value to an arbitrary value, causing the text to translucently show whatever window is beneath my application's. After calling rendering the text, I would like to go through all of the pixels in the control and set their alpha value back to 255. What's the best way to do that? I haven't had any luck with the BitBlt, GetPixel, and SetPixel functions. They appear to be oblivious to the alpha value. Here are other solutions that I have considered and rejected: Draw to a bitmap, then copy the bitmap to the device: With this approach, the text rendering does not make use of the characteristics of the monitor (e.g., ClearText). Use GDI+ for text rendering: This application originally used GDI+ for text rendering (before I started working on Aero support). I switched to GDI because of difficulties I encountered trying to accurately measure strings with GDI+. I'd rather not switch back. Set the Aero region to avoid the control in question: My application's window is actually a child window of a different application running in a different process. I don't have direct control over the Aero settings on the top-level window. The application is written in C# using Windows Forms, though I'm not above using Interop to call Win32 API functions.

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• Porting Python algorithm to C++ - different solution

  - by cb0

  Hello, I have written a little brute string generation script in python to generate all possible combinations of an alphabet within a given length. It works quite nice, but for the reason I wan't it to be faster I try to port it to C++. The problem is that my C++ Code is creating far too much combination for one word. Heres my example in python: ./test.py gives me aaa aab aac aad aa aba .... while ./test (the c++ programm gives me) aaa aaa aaa aaa aa Here I also get all possible combinations, but I get them twice ore more often. Here is the Code for both programms: #!/usr/bin/env python import sys #Brute String Generator #Start it with ./brutestringer.py 4 6 "abcdefghijklmnopqrstuvwxyz1234567890" "" #will produce all strings with length 4 to 6 and chars from a to z and numbers 0 to 9 def rec(w, p, baseString): for c in "abcd": if (p<w - 1): rec(w, p + 1, baseString + "%c" % c) print baseString for b in range(3,4): rec(b, 0, "") And here the C++ Code #include <iostream> using namespace std; string chars="abcd"; void rec(int w,int b,string p){ unsigned int i; for(i=0;i<chars.size();i++){ if(b < (w-1)){ rec(w, (b+1), p+chars[i]); } cout << p << "\n"; } } int main () { int a=3, b=0; rec (a+1,b, ""); return 0; } Does anybody see my fault ? I don't have much experience with C++. Thanks indeed

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• session variables in an ASP.NET

  - by Beep

  hi guy i am trying to place my session in to a drop down, any help would be great. at the moment it puts the data in to a label, i wish to put it into a dropdown with it adding a new string every time i click button without getting rid of the last default page protected void Button1_Click1(object sender, EventArgs e) { Session["Fruitname"] = TbxName.Text; // my session i have made } output page protected void Page_Load(object sender, EventArgs e) { var fruitname = Session["Fruitname"] as String; // my session ive made fruit.Text = fruitname; // session used in lable } Have Tried var myFruits = Session["Fruitname"] as List<string>; myFruits.Add(listbox1.Text); but i get error when i try to run the program Broken glass thanks for your help, it is still not doing what i need but its getting there. var fruitname = Session["Fruitname"] as String; // my session ive made fruit.Text = string.Join(",", fruitname); // session used in lable this is what is working. i need a dropdown to display all the strings put into TbxName.Text; to output into fruit

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• HELP Retrieving the url parameter from a JSON store from a EXTJS ComboBox

  - by Newbie

  I am having a problem retrieving the parameters from the url section of a json store for a combobox in EXTJS from my code behind page in c#. The following is the code in the store: var ColorStore = new Ext.data.JsonStore( { autoLoad: true, url: '/proxies/ReturnJSON.aspx?view=rm_colour_view', root: 'Rows', fields: ['company', 'raw_mat_col_code', 'raw_mat_col_desc'] }); And the following code is in my code behind page: protected void Page_Load(object sender, EventArgs e) { string jSonString = ""; connectionClass.connClass func = new connectionClass.connClass(); DataTable dt = func.getDataTable("sELECT * from rm_colour_view"); //Response.Write(Request.QueryString["view"]); string w = Request.Params.Get("url"); string z = Request.Params.Get("view"); string x = Request.Params.Get("view="); string c = Request.Params.Get("?view"); string s = Request.QueryString.Get("view"); string d = Request.Params["?view="]; string f = Request.Form["ColorStore"]; jSonString = Serialize(dt); Response.Write(jSonString); } The string w has gives the following output: /proxies/ReturnJSON.aspx but all the others strings return null... How can rm_colour_view from the datastore then be retrived??? Any help would be appreciated! Thanks

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• Jumping onto next string when the condition is met

  - by user98235

  This was a problem related to one of the past topcoder exam problems called HowEasy. Let's assume that we're given a sentence, for instance, "We a1re really awe~~~some" I just wanted to take get rid of every word in the sentence that doesn't contain alphabet characters, so in the above sentence, the desired output would be "We really" The below is the code I wrote (incomplete), and I don't know how to move on to the next string when the condition (the string contains a character that's not alphabet) is met. Could you suggest some revisions or methods that would allow me to do that? vect would be the vector of strings containing the desired output string param; cin>>param; stringstream ss(param); vector<string> vect; string c; while(ss >> c){ for(int i=0; i < c.length(); i++){ if(!(97<=int(c[i])&&int(c[i])<=122) && !(65<=int(c[i])&&int(c[i])<=90)){ //I want to jump onto next string once the above condition is met //and ignore string c; } vect.push_back(c); if (ss.peek() == ' '){ ss.ignore(); } } }

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• What's the best way to handle layout issues with multi-language support in WPF/XAML?

  - by Tim

  I'm creating a standalone WPF app with multi-language support. I've found some great resources (mostly on SO) on how to store and access the strings as needed. This part is pretty straightforward and doable, but I'm fuzzy on how to take care of screen layout issues. I'm using some custom images to skin up my app for buttons, etc. For instance, here's a button with some text within: <Button Canvas.Left="33" Canvas.Top="484" Style="{StaticResource SmallButtonBase}"> <TextBlock FontSize="20" FontWeight="Bold" TextAlignment="Center" FontFamily="Helvetica"> Enter </TextBlock> </Button> Now here is the same button with text from another language: <Button Canvas.Left="33" Canvas.Top="484" Style="{StaticResource SmallButtonBase}"> <TextBlock FontSize="20" FontWeight="Bold" TextAlignment="Center" FontFamily="Helvetica"> Enterenschtein </TextBlock> </Button> So my question is: What is a good method to prevent this "overflow" situation. I'd like to have XAML take care of any font resizing or indenting that is needed automatically so that I don't have to tweak the UI for each language I'm supporting. Any insight is appreciated!

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• Within a DLL, how is the function table structured?

  - by Willi Ballenthin

  I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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• C preprocessor problem in Microsoft Visual Studio 2010

  - by Remo.D

  I've encountered a problem with the new Visual C++ in VS 2010. I've got a header with the following defines: #define STC(y) #y #define STR(y) STC(\y) #define NUM(y) 0##y The intent is that you can have some constant around like #define TOKEN x5A and then you can have the token as a number or as a string: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\x5A" This is the expected behavior under the the substitution rules of macros arguments and so far it has worked well with gcc, open watcom, pellesC (lcc), Digital Mars C and Visual C++ in VS2008 Express. Today I recompiled the library with VS2010 Express only to discover that it doesn't work anymore! Using the new version I would get: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\y" It seems that the new preprocessor treats \y as an escape sequence even within a macro body which is a non-sense as escape sequences only have a meaning in literal strings. I suspect this is a gray area of the ANSI standard but even if the original behavior was mandated by the standard, MS VC++ is not exactly famous to be 100% ANSI C compliant so I guess I'll have to live with the new behavior of the MS compiler. Given that, does anybody have a suggestion on how to re-implement the original macros behavior with VS2010?

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• Java: Inputting text from a file using split

  - by 00PS

  I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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• Stopping process in /etc/inittab kills spawned process. Doesn't happen in rc.local.

  - by Paul

  Hi, I'm trying to execute a firmware upgrade while my programming is running in inittab. My program will run 2 commands. One to extract the installer script from the tarball and the other to execute the installer script. In my code I'm using the system() function call. These are the 2 command strings below, system ( "tar zvxf tarball.tar.gz -C / installer.sh 2>&1" ); system( "nohup installer.sh tarball >/dev/null 2>&1 &" ); The installer script requires the tarball to be an argument. I've tried using sudo but i still have the same problem. I've tried nohup with no success. The installer script has to kill my program when doing the firmware upgrade but the installer script will stay alive. If my program is run from the command line or rc.local, on my target device, my upgrade works fine, i.e. when my program is killed my installer script continues. But I need to run my program from /etc/inittab so it can respawn if it dies. To stop my program in inittab the installer script will hash it out and execute "telinit q". This is where my program dies (but thats what I want it to do), but it also kills my installer script. Does anyone know why this is happening and what can I do to solve it? Thanks in advance.

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• Confusion in MIPS code

  - by Haya Hallian

  While going through the MIPS code I got some confusion. Code is shown as follows .data key: .ascii "key: " # "key: \n" char: .asciiz " \n" .text .globl main main: jal getchar la $a0, char # $a0 contains address of char variable (" \n") sb $v0, ($a0) # replace " " in char with v0, which is read_character (X) la $a0, key # now a0 will contain, address of "key: " "X\n" What I dont understand is that how load address instruction works. First a0 contained address of char variable. In next line we are storing value of v0 in that location. there is no offset with ($a0), is that assumed to be 0 like in 0($a0)? Why only the " " empty space is replaced with v0, and why not the "\n" get replaced? or It may also have been the case that both the empty space and \n character get replced by v0. Secondly when we load the address of key in a0, the previous address should be overwritten. a0 should have contained the address of key only, but from comment it seems that the two strings are concatenated. How does that happen.

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• What would happen if a same file being read and appended at the same time(python programming)?

  - by Shane

  I'm writing a script using two separate thread one doing file reading operation and the other doing appending, both threads run fairly frequently. My question is, if one thread happens to read the file while the other is just in the middle of appending strings such as "This is a test" into this file, what would happen? I know if you are appending a smaller-than-buffer string, no matter how frequently you read the file in other threads, there would never be incomplete line such as "This i" appearing in your read file, I mean the os would either do: append "This is a test" - read info from the file; or: read info from the file - append "This is a test" to the file; and such would never happen: append "This i" - read info from the file - append "s a test". But if "This is a test" is big enough(assuming it's a bigger-than-buffer string), the os can't do appending job in one operation, so the appending job would be divided into two: first append "This i" to the file, then append "s a test", so in this kind of situation if I happen to read the file in the middle of the whole appending operation, would I get such result: append "This i" - read info from the file - append "s a test", which means I might read a file that includes an incomplete string?

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• Pointer and malloc issue

  - by Andy

  I am fairly new to C and am getting stuck with arrays and pointers when they refer to strings. I can ask for input of 2 numbers (ints) and then return the one I want (first number or second number) without any issues. But when I request names and try to return them, the program crashes after I enter the first name and not sure why. In theory I am looking to reserve memory for the first name, and then expand it to include a second name. Can anyone explain why this breaks? Thanks! #include <stdio.h> #include <stdlib.h> void main () { int NumItems = 0; NumItems += 1; char* NameList = malloc(sizeof(char[10])*NumItems); printf("Please enter name #1: \n"); scanf("%9s", NameList[0]); fpurge(stdin); NumItems += 1; NameList = realloc(NameList,sizeof(char[10])*NumItems); printf("Please enter name #2: \n"); scanf("%9s", NameList[1]); fpurge(stdin); printf("The first name is: %s",NameList[0]); printf("The second name is: %s",NameList[1]); return 0; }

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• How can I write a function template for all types with a particular type trait?

  - by TC

  Consider the following example: struct Scanner { template <typename T> T get(); }; template <> string Scanner::get() { return string("string"); } template <> int Scanner::get() { return 10; } int main() { Scanner scanner; string s = scanner.get<string>(); int i = scanner.get<int>(); } The Scanner class is used to extract tokens from some source. The above code works fine, but fails when I try to get other integral types like a char or an unsigned int. The code to read these types is exactly the same as the code to read an int. I could just duplicate the code for all other integral types I'd like to read, but I'd rather define one function template for all integral types. I've tried the following: struct Scanner { template <typename T> typename enable_if<boost::is_integral<T>, T>::type get(); }; Which works like a charm, but I am unsure how to get Scanner::get<string>() to function again. So, how can I write code so that I can do scanner.get<string>() and scanner.get<any integral type>() and have a single definition to read all integral types? Update: bonus question: What if I want to accept more than one range of classes based on some traits? For example: how should I approach this problem if I want to have three get functions that accept (i) integral types (ii) floating point types (iii) strings, respectively.

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