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  • what does "out of range" mean?

    - by user329820
    Hi I have checked these statements with mysql and no error will happen and also the out put will be 0 rows BUT my friend checked it and he found an error for SELECT becaouse it is out of range !! IS he correct? thanks CREATE TABLE T1(A INTEGER NULL); SELECT * FROM T1;

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  • Haskell Add Function Return to List Until Certain Length

    - by kienjakenobi
    I want to write a function which takes a list and constructs a subset of that list of a certain length based on the output of a function. If I were simply interested in the first 50 elements of the sorted list xs, then I would use fst (splitAt 50 (sort xs)). However, the problem is that elements in my list rely on other elements in the same list. If I choose element p, then I MUST also choose elements q and r, even if they are not in the first 50 elements of my list. I am using a function finderFunc which takes an element a from the list xs and returns a list with the element a and all of its required elements. finderFunc works fine. Now, the challenge is to write a function which builds a list whose total length is 50 based on multiple outputs of finderFunc. Here is my attempt at this: finish :: [a] -> [a] -> [a] --This is the base case, which adds nothing to the final list finish [] fs = [] --The function is recursive, so the fs variable is necessary so that finish -- can forward the incomplete list to itself. finish ps fs -- If the final list fs is too small, add elements to it | length fs < 50 && length (fs ++ newrs) <= 50 = fs ++ finish newps newrs -- If the length is met, then add nothing to the list and quit | length fs >= 50 = finish [] fs -- These guard statements are currently lacking, not the main problem | otherwise = finish [] fs where --Sort the candidate list sortedps = sort ps --(finderFunc a) returns a list of type [a] containing a and all the -- elements which are required to go with it. This is the interesting -- bit. rs is also a subset of the candidate list ps. rs = finderFunc (head sortedps) --Remove those elements which are already in the final list, because -- there can be overlap newrs = filter (`notElem` fs) rs --Remove the elements we will add to the list from the new list -- of candidates newps = filter (`notElem` rs) ps I realize that the above if statements will, in some cases, not give me a list of exactly 50 elements. This is not the main problem, right now. The problem is that my function finish does not work at all as I would expect it to. Not only does it produce duplicate elements in the output list, but it sometimes goes far above the total number of elements I want to have in the list. The way this is written, I usually call it with an empty list, such as: finish xs [], so that the list it builds on starts as an empty list.

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  • Using [self method] or @selector(method)?

    - by fuzzygoat
    Can anyone enlighten me as to the differences between the two statements below. [self playButtonSound]; AND: [self performSelector:@selector(playButtonSound)]; I am just asking as I had some old code that used @selector, now with a little more knowledge I can't think why I did not use [self playButtonSound] instead, they both seem to do the same as written here. gary

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  • How to disable activerecord cache logging in rails

    - by user1508459
    I'm trying to disable logging of caching in production. Have succeeded in getting SQL to stop logging queries, but no luck with caching log entries. Example line in production log: CACHE (0.0ms) SELECT merchants.* FROM merchants WHERE merchants.id = 1 LIMIT 1 I do not want to disable all logging, since I want logger.debug statements to show up in the production log. Using rails 3.2.1 with Mysql and Apache. Any suggestions?

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  • Python - How is this snippet working?

    - by orokusaki
    For some reason this function confused me: def protocol(port): return port == "443" and "https://" or "http://" Can somebody explain the order of what's happening behind the scenes to make this work the way it does. I understood it as this until I tried it: Either A) def protocol(port): if port == "443": if bool("https://"): return True elif bool("http://"): return True return False Or B) def protocol(port): if port == "443": return True + "https://" else: return True + "http://" Is this some sort of special case in Python, or am I completely misunderstanding how statements work?

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  • C++: Short question regarding switch and break

    - by oh boy
    Example: switch( x ) { case y: if ( true ) { break; } cout << "Oops"; break; } If the switch statement selects y, will Oops be written to the standard output? - Is break in switch statements a dynamic keyword like continue which can be called under conditions or static like a closing bracket }?

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  • require_once at the beginning or when really needed?

    - by takeshin
    Where should I put require_once statements, and why? Always on the beginning of a file, before the class, In the actual method when the file is really needed It depends ? Most frameworks put includes at the beginning and do not care if the file is really needed. Using autoloader is the other case here.

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  • seperated mysql statement query in php

    - by stone
    So, I can run the following statements from within mysql itself successfully. SET @fname = 'point1'; SELECT * FROM country WHERE name=@fname;` But when I try to pass the query through php like this and run it, I get an error on the second line $query = "SET @fname = 'point1';"; $query .= "SELECT * FROM country WHERE name=@fname;";

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  • Does there exists a method to render an object using DebuggerDisplayAttribute

    - by Joe
    I have a number of classes that are decorated with DebuggerDisplayAttribute. I want to be able to add trace statements to Unit Tests that will display instances of these classes. Does there exist a method in the .NET Framework that will display an object formatted using DebuggerDisplayAttribute (or fall back to using .ToString() if no DebuggerDisplayAttribute is defined)?

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  • patterns in case statement in bash scripting

    - by Ramiro Rela
    The man says that case statements use "filename expansion pattern matching". I usually want to have short names for some parameters, so I go: case $1 in req|reqs|requirements) TASK="Functional Requirements";; met|meet|meetings) TASK="Meetings with the client";; esac logTimeSpentIn "$TASK" I tried patterns like "req*" or "me{e,}t" which I understand would expand correctly to match those values in the context of filename expansion, but it doesn't work. Thanks.

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  • insert exclusive locking

    - by Markus
    Hi, I have thought about the following SQL statements: INSERT INTO A(a1, a2) SELECT b1, udf_SomeFunc(b1) FROM B Where udf_SomeFunc makes a select on table A. As I understand, first, a shared lock is set on A (I am talking just about table A now), then, after this lock is released, an exclusive lock is obtained to insert the data. The question is: is it possible, that another transaction will get the exclusive lock on table A, just before the current transaction takes its exclusive lok on A?

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  • Assign a list of integers to an @var

    - by justSteve
    I can: declare @idOrder int set @idOrder = 21319 I want: declare @idOrder int set @idOrder = (21319, 21320) for use in a series of statements where the 'WHERE' clause uses the IN operator delete Orders where idOrder in @idOrder instead of delete Orders where idOrder in (21319, 21320)

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  • SQL - Conditionally evaluate WHERE clauses

    - by Crimius
    I need to get a WHERE clause to only evaluate certain statements. something like: WHERE field_a = field_b AND (CASE WHEN <PARAM>type</PARAM> = 5 THEN {field_c = 1 OR field_c = 2} WHEN <PARAM>type</PARAM> = 6 THEN {field_c = 3 OR field_c = 4} ELSE field_c = <PARAM>type</PARAM> so that when the Param type = 5, it only checks if field_c = 1 or 2. Any thoughts?

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  • How can I map a String to a function in Java?

    - by Bears will eat you
    Currently, I have a bunch of Java classes that implement a Processor interface, meaning they all have a processRequest(String key) method. The idea is that each class has a few (say, <10) member Strings, and each of those maps to a method in that class via the processRequest method, like so: class FooProcessor implements Processor { String key1 = "abc"; String key2 = "def"; String key3 = "ghi"; // and so on... String processRequest(String key) { String toReturn = null; if (key1.equals(key)) toReturn = method1(); else if (key2.equals(key)) toReturn = method2(); else if (key3.equals(key)) toReturn = method3(); // and so on... return toReturn; } String method1() { // do stuff } String method2() { // do other stuff } String method3() { // do other other stuff } // and so on... } You get the idea. This was working fine for me, but now I need a runtime-accessible mapping from key to function; not every function actually returns a String (some return void) and I need to dynamically access the return type (using reflection) of each function in each class that there's a key for. I already have a manager that knows about all the keys, but not the mapping from key to function. My first instinct was to replace this mapping using if-else statements with a Map<String, Function>, like I could do in Javascript. But, Java doesn't support first-class functions so I'm out of luck there. I could probably dig up a third-party library that lets me work with first-class functions, but I haven't seen any yet, and I doubt that I need an entire new library. I also thought of putting these String keys into an array and using reflection to invoke the methods by name, but I see two downsides to this method: My keys would have to be named the same as the method - or be named in a particular, consistent way so that it's easy to map them to the method name. This seems WAY slower than the if-else statements I have right now. Efficiency is something of a concern because these methods will tend to get called pretty frequently, and I want to minimize unnecessary overhead. TL; DR: I'm looking for a clean, minimal-overhead way to map a String to some sort of a Function object that I can invoke and call (something like) getReturnType() on. I don't especially mind using a 3rd-party library if it really fits my needs. I also don't mind using reflection, though I would strongly prefer to avoid using reflection every single time I do a method lookup - maybe using some caching strategy that combines the Map with reflection. Thoughts on a good way to get what I want? Cheers!

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  • if with multiple conditions, order of execution

    - by markus
    Hi, In an if statement with multiple conditions is second executed if the outcome is clear after checking the first condition? example: if(i>0 && array[i]==0){ } If I swap the conditions a seg fault may occur for negative values of i but this way the memory debugger doesn't find a problem. Can I be sure that this works always or do have have to use nested if statements?

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  • Using Oracle Zero Date

    - by Noam
    I have an application with existing data, that has Zero in the date column. When I look at it from sqlplus I see: 00-DECEMB when I use the dump function on this column, I Get: Typ=12 Len=7: 100,100,0,0,1,1,1 I need to work with the existing data from .Net (no changes to the data,or the data structure or even existing sql statements) How the hack do I read this value, or write it. The db version varies, from 8 to 11. Help would be appreciated

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  • Printing Variable names and contents as debugging tool; looking for emacs/Python shortcut

    - by Schof
    I find myself adding debugging "print" statements quite often -- stuff like this: print("a_variable_name: %s" % a_variable_name) How do you all do that? Am I being neurotic in trying to find a way to optimize this? I may be working on a function and put in a half-dozen or so of those lines, figure out why it's not working, and then cut them out again. Have you developed an efficient way of doing that? I'm coding Python in Emacs.

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