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  • Array of Structs Initialization....

    - by user69514
    Hi I am working on a program where I have to initialize a deck of cards. I am using a struct to represent a card. However I'm not filling it correctly as I get a bunch of zero's when I display the deck of cards. I believe my mistake is in this line but I'm not sure: struct card temp = {"Clubs", value, false}; The code: void initCards(){ int count = 0; int location = 0; const int hand = 12; //add hearts int value=2; while( count < hand ){ struct card temp = {"Hearts", value, false}; cards[location] = temp; value++; count++; } count = 0; //add diamonts value = 2; while( count < hand ){ struct card temp = {"Diamonds", value, false}; cards[count] = temp; value++; count++; } //add spades count = 0; value = 2; while( count < hand ){ struct card temp = {"Spades", value, false}; cards[count] = temp; value++; count++; } //add clubs count = 0; value = 2; while( count < hand ){ struct card temp = {"Clubs", value, false}; cards[count] = temp; value++; count++; } //print the deck for(int i=0; i<52; i++){ cout << cards[i].type << " " << cards[i].rank << endl; } }

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  • C++ arrays as parameters, EDIT: now includes variable scoping

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong? EDIT Oh fun, I have a typo: it wasn't void someFunction(double results[]). It was: void someFunction(double result[])... So perhaps this is turning into a scoping question. If my double result[16] array is defined in a main.cpp, and someFunction is defined in a Utils.h file that's included by the main.cpp, does the result variable in someFunction then wreak havoc on the result array in main?

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  • lua metatable __lt __le __eq forced boolean conversion of return value

    - by chris g.
    Overloading __eq, __lt, and __le in a metatable always converts the returning value to a boolean. Is there a way to access the actual return value? This would be used in the following little lua script to create an expression tree for an argument usage: print(_.a + _.b - _.c * _.d + _.a) -> prints "(((a+b)-(c*d))+a)" which is perfectly what I would like to have but it doesn't work for print(_.a == _.b) since the return value gets converted to a boolean ps: print should be replaced later with a function processing the expression tree -- snip from lua script -- function binop(op1,op2, event) if op1[event] then return op1[event](op1, op2) end if op2[event] then return op2[event](op1, op2) end return nil end function eq(op1, op2)return binop(op1,op2, "eq") end ... function div(op1, op2)return binop(op1,op2, "div") end function exprObj(tostr) expr = { eq = binExpr("=="), lt = binExpr("<"), le = binExpr("<="), add = binExpr("+"), sub=binExpr("-"), mul = binExpr("*"), div= binExpr("/") } setmetatable(expr, { __eq = eq, __lt = lt, __le = le, __add = add, __sub = sub, __mul = mul, __div = div, __tostring = tostr }) return expr end function binExpr(exprType) function binExprBind(lhs, rhs) return exprObj(function(op) return "(" .. tostring(lhs) .. exprType .. tostring(rhs) .. ")" end) end return binExprBind end function varExpr(obj, name) return exprObj(function() return name end) end _ = {} setmetatable(_, { __index = varExpr }) -- snap -- Modifing the lua vm IS an option, however it would be nice if I could use an official release

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  • Linq.Where-to-SQL on a text field comparing to a list of values

    - by StampedeXV
    Customer.text is a field in an T-SQL DB (that I do not control and thus may not alter) of type "text". I'd like to do something like this: List<string> compare = new List<string>(); compare.Add("one"); compare.Add("two"); var q = from t in customer where t.text.Contains( compare.First()) select t; this will work. But now I'd like to do something like: (!NOT WORKING!) var q = from t in customer where compare.Contains( t.text ) select t; How can I achieve this? Is it even possible?

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  • PHP Simplify a ternary operation

    - by Obay
    In PHP, is there a way to simplify this even more, without using an if()? $foo = $bar!==0 ? $foo : ''; I was wondering if there was a way to not reassign $foo to itself if the condition is satisfied. I understand there is a way to do this in Javascript (using &&, right?), but was wondering if there was a way to do this in PHP.

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  • nothrow or exception ?

    - by Muggen
    I am a student and I have small knowledge on C++, which I try to expand. This is more of a philosophical question.. I am not trying to implement something. Since #include <new> //... T * t = new (std::nothrow) T(); if(t) { //... } //... Will hide the Exception, and since dealing with Exceptions is heavier compared to a simple if(t), why isn't the normal new T() not considered less good practice, considering we will have to use try-catch() to check if a simple allocation succeeded (and if we don't, just watch the program die)?? What are the benefits (if any) of the normal new allocation compared to using a nothrow new? Exception's overhead in that case is insignificant ? Also, Assume that an allocation fails (eg. no memory exists in the system). Is there anything the program can do in that situation, or just fail gracefully. There is no way to find free memory on the heap, when all is reserved, is there? Incase an allocation fails, and an std::bad_alloc is thrown, how can we assume that since there is not enough memory to allocate an object (Eg. a new int), there will be enough memory to store an exception ?? Thanks for your time. I hope the question is in line with the rules.

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  • Problem with java and conditional (game of life)

    - by Muad'Dib
    Hello everybody, I'm trying to implement The Game of Life in java, as an exercise to learn this language. Unfortunately I have a problem, as I don't seem able to make this program run correctly. I implemented a torodial sum (the plane is a donut) with no problem: int SumNeighbours (int i, int j) { int value = 0; value = world[( i - 1 + row ) % row][( j - 1 + column ) % column]+world[( i - 1 + row ) % row][j]+world[( i - 1 + row ) % row][( j + 1 ) % column]; value = value + world[i][( j - 1 + column ) % column] + world[i][( j + 1 ) % column]; value = value + world[( i + 1 ) % row][( j - 1 + column ) % column] + world[( i + 1 ) % row][j]+world[ ( i+1 ) % row ][( j + 1 ) % column]; return value; } And it sums correctly when I test it: void NextWorldTest () { int count; int [][] nextWorld = new int[row][row]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); } System.out.println(); } world=nextWorld; } Unfortunately when I add the conditions of game of life (born/death) the program stop working correctly, as it seems not able anymore to count correctly the alive cells in the neighborhood. It counts where there are none, and it doesn't count when there are some. E.g.: it doesn't count the one below some living cells. It's a very odd behaviour, and it's been giving me a headache for 3 days now... maybe I'm missing something basic about variables? Here you can find the class. void NextWorld () { int count; int [][] nextWorld = new int[row][column]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); if ( ( world[i][j] == 0) && ( count == 3 ) ) { nextWorld[i][j] = 1; } else if ( ( world[i][j] == 1 ) && ( (count == 3) || (count == 2) )) { nextWorld[i][j] = 1; } else { nextWorld[i][j]=0; } } System.out.println(); } world=nextWorld; } } Am I doing something wrong? Below you can find the full package. package com.GaOL; public class GameWorld { int [][] world; int row; int column; public int GetRow() { return row; } public int GetColumn() { return column; } public int GetWorld (int i, int j) { return world[i][j]; } void RandomGen (int size, double p1) { double randomCell; row = size; column = size; world = new int[row][column]; for (int i = 0; i<row; i++ ) { for (int j = 0; j<column; j++ ) { randomCell=Math.random(); if (randomCell < 1-p1) { world[i][j] = 0; } else { world[i][j] = 1; } } } } void printToConsole() { double test = 0; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { if ( world[i][j] == 0 ) { System.out.print(" "); } else { System.out.print(" * "); test++; } } System.out.println(""); } System.out.println("ratio is " + test/(row*column)); } int SumNeighbours (int i, int j) { int value = 0; value = world[( i - 1 + row ) % row][( j - 1 + column ) % column]+world[( i - 1 + row ) % row][j]+world[( i - 1 + row ) % row][( j + 1 ) % column]; value = value + world[i][( j - 1 + column ) % column] + world[i][( j + 1 ) % column]; value = value + world[( i + 1 ) % row][( j - 1 + column ) % column] + world[( i + 1 ) % row][j]+world[ ( i+1 ) % row ][( j + 1 ) % column]; return value; } void NextWorldTest () { int count; int [][] nextWorld = new int[row][row]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); } System.out.println(); } world=nextWorld; } void NextWorld () { int count; int [][] nextWorld = new int[row][column]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); if ( ( world[i][j] == 0) && ( count == 3 ) ) { nextWorld[i][j] = 1; } else if ( ( world[i][j] == 1 ) && ( (count == 3) || (count == 2) )) { nextWorld[i][j] = 1; } else { nextWorld[i][j]=0; } } System.out.println(); } world=nextWorld; } } and here the test class: package com.GaOL; public class GameTestClass { public static void main(String[] args) { GameWorld prova = new GameWorld(); prova.RandomGen(10, 0.02); for (int i=0; i<3; i++) { prova.printToConsole(); prova.NextWorld(); } } }

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  • In C what is the difference between null and a new line character? Guys help please [migrated]

    - by Siddhartha Gurjala
    Whats the conceptual difference and similarity between NULL and a newline character i.e between '\0' and '\n' Explain their relevance for both integer and character data type variables and arrays? For reference here is an example snippets of a program to read and write a 2d char array PROGRAM CODE 1: int main() { char sort(),stuname(),swap(),(*p)(),(*q)(); int n; p=stuname; q=swap; printf("Let the number of students in the class be \n"); scanf("%d",&n); fflush(stdin); sort(p,q,n); return 0; } char sort(p1,q1,n1) char (*p1)(),(*q1)(); int n1; { (*p1)(n1); (*q1)(); } char stuname(int nos) // number of students { char name[nos][256]; int i,j; printf("Reading names of %d students started--->\n\n",nos); name[0][0]='k'; //initialising as non NULL charecter for(i=0;i<nos;i++) // nos=number of students { printf("Give name of student %d\n",i); for(j=0;j<256;j++) { scanf("%c",&name[i][j]); if(name[i][j]=='\n') { name[i][j]='\0'; j=257; } } } printf("\n\nWriting student names:\n\n"); for(i=0;i<nos;i++) { for(j=0;j<256&&name[i][j]!='\0';j++) { printf("%c",name[i][j]); } printf("\n"); } } char swap() { printf("Will swap shortly after getting clarity on scanf and %c"); } The above code is working good where as the same logic given with slight diff is not giving appropriate output. Here's the code PROGRAM CODE 2: #include<stdio.h> int main() { char sort(),stuname(),swap(),(*p)(),(*q)(); int n; p=stuname; q=swap; printf("Let the number of students in the class be \n"); scanf("%d",&n); fflush(stdin); sort(p,q,n); return 0; } char sort(p1,q1,n1) char (*p1)(),(*q1)(); int n1; { (*p1)(n1); (*q1)(); } char stuname(int nos) // number of students { char name[nos][256]; int i,j; printf("Reading names of %d students started--->\n\n",nos); name[0][0]='k'; //initialising as non NULL charecter for(i=0;i<nos;i++) // nos=number of students { printf("Give name of student %d\n",i); ***for(j=0;j<256&&name[i][j]!='\0';j++)*** { scanf("%c",&name[i][j]); /*if(name[i][j]=='\n') { name[i][j]='\0'; j=257; }*/ } } printf("\n\nWriting student names:\n\n"); for(i=0;i<nos;i++) { for(j=0;j<256&&name[i][j]!='\0';j++) { printf("%c",name[i][j]); } printf("\n"); } } char swap() { printf("Will swap shortly after getting clarity on scanf and %c"); } Here one more instance of same program not giving proper output given below PROGRAM CODE 3: #include<stdio.h> int main() { char sort(),stuname(),swap(),(*p)(),(*q)(); int n; p=stuname; q=swap; printf("Let the number of students in the class be \n"); scanf("%d",&n); fflush(stdin); sort(p,q,n); return 0; } char sort(p1,q1,n1) char (*p1)(),(*q1)(); int n1; { (*p1)(n1); (*q1)(); } char stuname(int nos) // number of students { char name[nos][256]; int i,j; printf("Reading names of %d students started--->\n\n",nos); name[0][0]='k'; //initialising as non NULL charecter for(i=0;i<nos;i++) // nos=number of students { printf("Give name of student %d\n",i); ***for(j=0;j<256&&name[i][j]!='\n';j++)*** { scanf("%c",&name[i][j]); /*if(name[i][j]=='\n') { name[i][j]='\0'; j=257; }*/ } name[i][i]='\0'; } printf("\n\nWriting student names:\n\n"); for(i=0;i<nos;i++) { for(j=0;j<256&&name[i][j]!='\0';j++) { printf("%c",name[i][j]); } printf("\n"); } } char swap() { printf("Will swap shortly after getting clarity on scanf and %c"); } Why the program code 2 and program code 3 are not working as expected as that of the code 1?

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  • returning null vs returning zero, which would be better?

    - by Dark Star1
    I inherited a project that I am managing and having to maintain pending the redevelopment of the code base. At the moment I am being tasked with adding little feature all over the place and have gotten into the habit of returning null instead of zero in parts of the code where I am working on. The problem is we have a client that is using this code and parts of code that require data from my implemented features recieve a null and dump the stack trace in UI. I would like to avoid this entirely from my input but without the nullPointer exceptions there's the potential that errors would be introduced into the client's data which may go un-noticed. Usually I would have come up with my own error notification system but I have never inherited a project before. so I am unsure whether to continue down this path. I still believe that the stack dump is preferable to un-noticed data corruption/inaccuracies.

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  • How do you create links with a NULL or # in Drupal?

    - by blunders
    Trying to create folders for links where the parent has no content, it's just a folder. Need to be able to insert #, but Drupal is saying it's not a link. Just want the user to click it and nothing happen, the child of that menu item will already be being displayed without a click. Version: Drupal 6 (appears worked in D5) I've attempted the following: '', #, <#>, empty, <empty>, null, <null>, blank, <blank>, <none>, none, <answer> ...just kidding. ERROR: The path '<insert_non-url>' is either invalid or you do not have access to it. Question, just ask -- thanks!

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  • What does /dev/null mean in a shell script?

    - by rishiag
    I've started learning bash scripting by using this guide: http://www.tldp.org/LDP/abs/abs-guide.pdf However I got stuck at the first script: cd /var/log cat /dev/null > messages cat /dev/null > wtmp echo "Log files cleaned up." What do lines 2 and 3 do in Ubuntu (I understand cat)? Is it only for other Linux distributions? After running this script as root, the output I get is Log files cleaned up. But /var/log still contains all the files.

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  • Why does Linq to Entity Sum return null when the list is empty?

    - by Hannele
    There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. Now, I could go a flag these as duplicates, but I feel it is still an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty list. But because the result of the Sum extension for nullable types is also not nullable, why would the Linq to SQL / Linq to Entity Sum have been designed to behave this way?

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  • Why does Linq to Entity Sum return null when the result set is empty?

    - by Hannele
    There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. I feel it is an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty result set. But because the result of the Sum extension for non-nullable types is also non-nullable, why does the Linq to SQL / Linq to Entity Sum behave this way?

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  • should std::auto_ptr<>::operator = reset / deallocate its existing pointee ?

    - by afriza
    I read here about std::auto_ptr<::operator= Notice however that the left-hand side object is not automatically deallocated when it already points to some object. You can explicitly do this by calling member function reset before assigning it a new value. However, when I read the source code for header file C:\Program Files\Microsoft Visual Studio 8\VC\ce\include\memory template<class _Other> auto_ptr<_Ty>& operator=(auto_ptr<_Other>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr<_Ty>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr_ref<_Ty> _Right) _THROW0() { // assign compatible _Right._Ref (assume pointer) _Ty **_Pptr = (_Ty **)_Right._Ref; _Ty *_Ptr = *_Pptr; *_Pptr = 0; // release old reset(_Ptr); // set new return (*this); } What is the correct/standard behavior? How do other STL implementations behave?

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  • How to make MySQL utilize available system resources, or find "the real problem"?

    - by anonymous coward
    This is a MySQL 5.0.26 server, running on SuSE Enterprise 10. This may be a Serverfault question. The web user interface that uses these particular queries (below) is showing sometimes 30+, even up to 120+ seconds at the worst, to generate the pages involved. On development, when the queries are run alone, they take up to 20 seconds on the first run (with no query cache enabled) but anywhere from 2 to 7 seconds after that - I assume because the tables and indexes involved have been placed into ram. From what I can tell, the longest load times are caused by Read/Update Locking. These are MyISAM tables. So it looks like a long update comes in, followed by a couple 7 second queries, and they're just adding up. And I'm fine with that explanation. What I'm not fine with is that MySQL doesn't appear to be utilizing the hardware it's on, and while the bottleneck seems to be the database, I can't understand why. I would say "throw more hardware at it", but we did and it doesn't appear to have changed the situation. Viewing a 'top' during the slowest times never shows much cpu or memory utilization by mysqld, as if the server is having no trouble at all - but then, why are the queries taking so long? How can I make MySQL use the crap out of this hardware, or find out what I'm doing wrong? Extra Details: On the "Memory Health" tab in the MySQL Administrator (for Windows), the Key Buffer is less than 1/8th used - so all the indexes should be in RAM. I can provide a screen shot of any graphs that might help. So desperate to fix this issue. Suffice it to say, there is legacy code "generating" these queries, and they're pretty much stuck the way they are. I have tried every combination of Indexes on the tables involved, but any suggestions are welcome. Here's the current Create Table statement from development (the 'experimental' key I have added, seems to help a little, for the example query only): CREATE TABLE `registration_task` ( `id` varchar(36) NOT NULL default '', `date_entered` datetime NOT NULL default '0000-00-00 00:00:00', `date_modified` datetime NOT NULL default '0000-00-00 00:00:00', `assigned_user_id` varchar(36) default NULL, `modified_user_id` varchar(36) default NULL, `created_by` varchar(36) default NULL, `name` varchar(80) NOT NULL default '', `status` varchar(255) default NULL, `date_due` date default NULL, `time_due` time default NULL, `date_start` date default NULL, `time_start` time default NULL, `parent_id` varchar(36) NOT NULL default '', `priority` varchar(255) NOT NULL default '9', `description` text, `order_number` int(11) default '1', `task_number` int(11) default NULL, `depends_on_id` varchar(36) default NULL, `milestone_flag` varchar(255) default NULL, `estimated_effort` int(11) default NULL, `actual_effort` int(11) default NULL, `utilization` int(11) default '100', `percent_complete` int(11) default '0', `deleted` tinyint(1) NOT NULL default '0', `wf_task_id` varchar(36) default '0', `reg_field` varchar(8) default '', `date_offset` int(11) default '0', `date_source` varchar(10) default '', `date_completed` date default '0000-00-00', `completed_id` varchar(36) default NULL, `original_name` varchar(80) default NULL, PRIMARY KEY (`id`), KEY `idx_reg_task_p` (`deleted`,`parent_id`), KEY `By_Assignee` (`assigned_user_id`,`deleted`), KEY `status_assignee` (`status`,`deleted`), KEY `experimental` (`deleted`,`status`,`assigned_user_id`,`parent_id`,`date_due`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 And one of the ridiculous queries in question: SELECT users.user_name assigned_user_name, registration.FIELD001 parent_name, registration_task.status status, registration_task.date_modified date_modified, registration_task.date_due date_due, registration.FIELD240 assigned_wf, if(LENGTH(registration_task.description)>0,1,0) has_description, registration_task.* FROM registration_task LEFT JOIN users ON registration_task.assigned_user_id=users.id LEFT JOIN registration ON registration_task.parent_id=registration.id where (registration_task.status != 'Completed' AND registration.FIELD001 LIKE '%' AND registration_task.name LIKE '%' AND registration.FIELD060 LIKE 'GN001472%') AND registration_task.deleted=0 ORDER BY date_due asc LIMIT 0,20; my.cnf - '[mysqld]' section. [mysqld] port = 3306 socket = /var/lib/mysql/mysql.sock skip-locking key_buffer = 384M max_allowed_packet = 100M table_cache = 2048 sort_buffer_size = 2M net_buffer_length = 100M read_buffer_size = 2M read_rnd_buffer_size = 160M myisam_sort_buffer_size = 128M query_cache_size = 16M query_cache_limit = 1M EXPLAIN above query, without additional index: +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ | 1 | SIMPLE | registration_task | ref | idx_reg_task_p,status_assignee | idx_reg_task_p | 1 | const | 1067354 | Using where; Using filesort | | 1 | SIMPLE | registration | eq_ref | PRIMARY,gbl | PRIMARY | 8 | sugarcrm401.registration_task.parent_id | 1 | Using where | | 1 | SIMPLE | users | ref | PRIMARY | PRIMARY | 38 | sugarcrm401.registration_task.assigned_user_id | 1 | | +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ EXPLAIN above query, with 'experimental' index: +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+ | 1 | SIMPLE | registration_task | range | idx_reg_task_p,status_assignee,NewIndex1,tcg_experimental | tcg_experimental | 259 | NULL | 103345 | Using where; Using filesort | | 1 | SIMPLE | registration | eq_ref | PRIMARY,gbl | PRIMARY | 8 | sugarcrm401.registration_task.parent_id | 1 | Using where | | 1 | SIMPLE | users | ref | PRIMARY | PRIMARY | 38 | sugarcrm401.registration_task.assigned_user_id | 1 | | +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+

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  • How to negate a predicate function using operator ! in C++?

    - by Chan
    Hi, I want to erase all the elements that do not satisfy a criterion. For example: delete all the characters in a string that are not digit. My solution using boost::is_digit worked well. struct my_is_digit { bool operator()( char c ) const { return c >= '0' && c <= '9'; } }; int main() { string s( "1a2b3c4d" ); s.erase( remove_if( s.begin(), s.end(), !boost::is_digit() ), s.end() ); s.erase( remove_if( s.begin(), s.end(), !my_is_digit() ), s.end() ); cout << s << endl; return 0; } Then I tried my own version, the compiler complained :( error C2675: unary '!' : 'my_is_digit' does not define this operator or a conversion to a type acceptable to the predefined operator I could use not1() adapter, however I still think the operator ! is more meaningful in my current context. How could I implement such a ! like boost::is_digit() ? Any idea? Thanks, Chan Nguyen

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  • Search SQL Question Between Related Two Tables

    - by mTuran
    Hi, I am writing some kind of search engine for my web application and i have a problem. I have 2 tables first of is projects table: PROJECTS TABLE id int(11) NO PRI NULL auto_increment employer_id int(11) NO MUL NULL project_title varchar(100) NO MUL NULL project_description text NO NULL project_budget int(11) NO NULL project_allowedtime int(11) NO NULL project_deadline datetime NO NULL total_bids int(11) NO NULL average_bid int(11) NO NULL created datetime NO MUL NULL active tinyint(1) NO MUL NULL PROJECTS_SKILLS TABLE project_id int(11) NO MUL NULL skill_id int(11) NO MUL NULL For example: I want ask this query to database: 1-) Skills are 5 and 7. 2-) Order results by created 3-) project title contains "php" word. 4-) Returned rows should contain projects.* columuns. 5-) Projects should be distinct(i don't want same projects in return of query). Please write sql query that ensure these conditions. Thank You.

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