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• Where can I find information on the Get, Set and Address methods for multidimensional System.Array i

  - by Rob Smallshire

  System.Array serves as the base class for all arrays in the Common Language Runtime (CLR). According to this article, For each concrete array type, [the] runtime adds three special methods: Get/Set/Address. and indeed if I disassemble this C# code, int[,] x = new int[1024,1024]; x[0,0] = 1; x[1,1] = 2; x[2,2] = 3; Console.WriteLine(x[0,0]); Console.WriteLine(x[1,1]); Console.WriteLine(x[2,2]); into CIL I get, IL_0000: ldc.i4 0x400 IL_0005: ldc.i4 0x400 IL_000a: newobj instance void int32[0...,0...]::.ctor(int32, int32) IL_000f: stloc.0 IL_0010: ldloc.0 IL_0011: ldc.i4.0 IL_0012: ldc.i4.0 IL_0013: ldc.i4.1 IL_0014: call instance void int32[0...,0...]::Set(int32, int32, int32) IL_0019: ldloc.0 IL_001a: ldc.i4.1 IL_001b: ldc.i4.1 IL_001c: ldc.i4.2 IL_001d: call instance void int32[0...,0...]::Set(int32, int32, int32) IL_0022: ldloc.0 IL_0023: ldc.i4.2 IL_0024: ldc.i4.2 IL_0025: ldc.i4.3 IL_0026: call instance void int32[0...,0...]::Set(int32, int32, int32) IL_002b: ldloc.0 IL_002c: ldc.i4.0 IL_002d: ldc.i4.0 IL_002e: call instance int32 int32[0...,0...]::Get(int32, int32) IL_0033: call void [mscorlib]System.Console::WriteLine(int32) IL_0038: ldloc.0 IL_0039: ldc.i4.1 IL_003a: ldc.i4.1 IL_003b: call instance int32 int32[0...,0...]::Get(int32, int32) IL_0040: call void [mscorlib]System.Console::WriteLine(int32) IL_0045: ldloc.0 IL_0046: ldc.i4.2 IL_0047: ldc.i4.2 IL_0048: call instance int32 int32[0...,0...]::Get(int32, int32) IL_004d: call void [mscorlib]System.Console::WriteLine(int32) where the calls to the aforementioned Get and Set methods can be clearly seen. It seems the arity of these methods is related to the dimensionality of the array, which is presumably why they are created by the runtime and are not pre-declared. I couldn't locate any information about these methods on MSDN and their simple names makes them resistant to Googling. I'm writing a compiler for a language which supports multidimensional arrays, so I'd like to find some official documentation about these methods, under what conditions I can expect them to exist and what I can expect their signatures to be. In particular, I'd like to know whether its possible to get a MethodInfo object for Get or Set for use with Reflection.Emit without having to create an instance of the array with correct type and dimensionality on which to reflect, as is done in the linked example.

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• how to create dynamic two dimensional array in java?

  - by Arivu2020

  i want to create two dimensional array dynamically.I know the number of columns.But the number of rows are changed dynamically.I try the array list,but it stores the value in single dimension only.what can i do?

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• How to pass an associative array as argument to a function in Bash?

  - by niksfirefly

  How do you pass an associative array as an argument to a function? Is this possible in Bash? The code below is not working as expected: function iterateArray { local ADATA="${@}" # associative array for key in "${!ADATA[@]}" do echo "key - ${key}" echo "value: ${ADATA[$key]}" done } Passing associative arrays to a function like normal arrays does not work: iterateArray "$A_DATA" or iterateArray "$A_DATA[@]"

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• How can I sort an array so that certain file extensions sort to the top?

  - by rarbox

  I have an array containing a list of files. I want to sort it in a way that it will let me have .txt files in the beginning of the array and the rest of files after that. This is what I'm doing now, which works fine. @files = (grep(/\.txt$/,@files),grep(!/\.txt$/,@files)); Is there a better way to do it though?

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• How do you make a 2-d array in Matlab?

  - by Ben Fossen

  I want to make a 2D array dij(i and j are subscripts). I want to be able to do dij = di,j-1+(di,j-1 - di-1,dj-1)/(4^j-1) My idea for this it to make to 1D arrays and then combine them into a 2D array. Is there an easier way to do this?

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• How can I multiply each item in an array easily with PHP?

  - by Henry

  I have an array called $times. It is a list of small numbers (15,14,11,9,3,2). These will be user submitted and are supposed to be minutes. As PHP time works on seconds, I would like to multiply each element of my array by 60. I've been playing around with array_walk and array_map but I can't get those working :S Thanks.

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• Delphi 6: How to search a dynamic array for sub-string quickly?

  - by Robert Oschler

  How can I search a dynamic array of char in Delphi 6 for a sub-string and get back an index to a match, not a pointer? I've seen functions in Delphi 6 that do this for strings but not for dynamic char arrays. There is a function called SearchBuf but that function returns a PChar pointer to the match location when what I need is the array index of the match. Thanks.

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• Java: change an element in a prepopulated List of string array.

  - by battousai622

  I have a List of string array already populated in storeInv. How do i change a specific element in the string array? For example the code below... Thanks =] List <String[]> storeInv ; //assume already populated with elements String[] store = storeInv.get(5); store[1] = 123; store.set(5, store[1]); //this gives me an error.

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• Is there a Pattern in Scala that add a method to an Array object?

  - by Fred Haslam

  Is there a Pattern in Scala that can add a method to an Array object? I am thinking of the implicit conversion of Int to RichInt. But that can't be done as Array is a final class.

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• how to pass an integeter array from a asp.net mvc controller action back to javascript using jquery

  - by oo

  Here is my jQuery code: $.get('/Home/GetList', function(data) { debugger; $('#myMultiSelect').val(data); }); Here is my controller code: public ActionResult GetList(int id) { int[] bodyParts = _repository.GetList(id); //how do i return this as an array back to javascript ?? } if I have the GetList function return an array of integers, how do I return this to the jQuery function?

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• how to pass an array from a asp.net mvc controller action back to javascript using jquery / ajax

  - by oo

  Here is my jQuery code: $.get('/Home/GetList', function(data) { debugger; $('#myMultiSelect').val(values); }); Here is my controller code: public ActionResult GetList(int id) { int[] bodyParts = _repository.GetList(id); //how do i return this as an array back to javascript ?? } if I have the GetList function return an array of integers, how do I return this to the jQuery function?

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• PHP - Checking whether a string exists in an entire array?

  - by RC

  Hi all, Basic array question: $string = "The quick brown cat"; $check1 = "apple"; $check2 = "ball"; $check3 = "cat"; if ( (stripos($string, $check1) === false) || (stripos($string, $check2) === false) || (stripos($string, $check3) === false) ) { echo "Fail"; } How do I condense the above using an array ($check[])? Thanks!

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• How allocate or free only parts of an array?

  - by drigoSkalWalker

  see this example: int *array = malloc (10 * sizeof(int)) Then free only the first 3 blocks? Or make equal java, have an array with negative index, or an index that not began with 0. Thanks a lot.

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• Is it okay to use array[key] in PHP?

  - by terrani

  Hi, I have a simple question. Is it okay to use array without single or double quotion like $array[key]? I thought it is bad because PHP look for constant first if I don't use single or doulbe quotion. One of my colleagues told me that it does not matter. WHat do you guys think?

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• Unable to access intel fake RAID 1 array in Fedora 14 after reboot

  - by Sim

  Hello everyone, 1st I am relatively new to linux (but not to *nix). I have 4 disks assembled in the following intel ahci bios fake raid arrays: 2x320GB RAID1 - used for operating systems md126 2x1TB RAID1 - used for data md125 I have used the raid of size 320GB to install my operating system and the second raid I didn't even select during the installation of Fedora 14. After successful partitioning and installation of Fedora, I tried to make the second array available, it was possible to make it visible in linux with mdadm --assembe --scan , after that I created one maximum size partition and 1 maximum size ext4 filesystem in it. Mounted, and used it. After restart - a few I/O errors during boot regarding md125 + inability to mount the filesystem on it and dropped into repair shell. I commented the filesystem in fstab and it booted. To my surprise, the array was marked as "auto read only": [root@localhost ~]# cat /proc/mdstat Personalities : [raid1] md125 : active (auto-read-only) raid1 sdc[1] sdd[0] 976759808 blocks super external:/md127/0 [2/2] [UU] md127 : inactive sdc[1](S) sdd[0](S) 4514 blocks super external:imsm md126 : active raid1 sda[1] sdb[0] 312566784 blocks super external:/md1/0 [2/2] [UU] md1 : inactive sdb[1](S) sda[0](S) 4514 blocks super external:imsm unused devices: <none> [root@localhost ~]# and the partition in it was not available as device special file in /dev: [root@localhost ~]# ls -l /dev/md125* brw-rw---- 1 root disk 9, 125 Jan 6 15:50 /dev/md125 [root@localhost ~]# But the partition is there according to fdisk: [root@localhost ~]# fdisk -l /dev/md125 Disk /dev/md125: 1000.2 GB, 1000202043392 bytes 19 heads, 10 sectors/track, 10281682 cylinders, total 1953519616 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x1b238ea9 Device Boot Start End Blocks Id System /dev/md125p1 2048 1953519615 976758784 83 Linux [root@localhost ~]# I tried to "activate" the array in different ways (I'm not experienced with mdadm and the man page is gigantic so I was only browsing it looking for my answer) but it was impossible - the array would still stay in "auto read only" and the device special file for the partition it will not be in /dev. It was only after I recreated the partition via fdisk that it reappeared in /dev... until next reboot. So, my question is - How do I make the array automatically available after reboot? Here is some additional information: 1st I am able to see the UUID of the array in blkid: [root@localhost ~]# blkid /dev/sdc: UUID="b9a1149f-ae11-4fc8-a600-0d77354dc42a" SEC_TYPE="ext2" TYPE="ext3" /dev/sdd: UUID="b9a1149f-ae11-4fc8-a600-0d77354dc42a" SEC_TYPE="ext2" TYPE="ext3" /dev/md126p1: UUID="60C8D9A7C8D97C2A" TYPE="ntfs" /dev/md126p2: UUID="3d1b38a3-b469-4b7c-b016-8abfb26a5d7d" TYPE="ext4" /dev/md126p3: UUID="1Msqqr-AAF8-k0wi-VYnq-uWJU-y0OD-uIFBHL" TYPE="LVM2_member" /dev/mapper/vg00-rootlv: LABEL="_Fedora-14-x86_6" UUID="34cc1cf5-6845-4489-8303-7a90c7663f0a" TYPE="ext4" /dev/mapper/vg00-swaplv: UUID="4644d857-e13b-456c-ac03-6f26299c1046" TYPE="swap" /dev/mapper/vg00-homelv: UUID="82bd58b2-edab-4b4b-aec4-b79595ecd0e3" TYPE="ext4" /dev/mapper/vg00-varlv: UUID="1b001444-5fdd-41b6-a59a-9712ec6def33" TYPE="ext4" /dev/mapper/vg00-tmplv: UUID="bf7d2459-2b35-4a1c-9b81-d4c4f24a9842" TYPE="ext4" /dev/md125: UUID="b9a1149f-ae11-4fc8-a600-0d77354dc42a" SEC_TYPE="ext2" TYPE="ext3" /dev/sda: TYPE="isw_raid_member" /dev/md125p1: UUID="420adfdd-6c4e-4552-93f0-2608938a4059" TYPE="ext4" [root@localhost ~]# Here is how /etc/mdadm.conf looks like: [root@localhost ~]# cat /etc/mdadm.conf # mdadm.conf written out by anaconda MAILADDR root AUTO +imsm +1.x -all ARRAY /dev/md1 UUID=89f60dee:e46a251f:7475814b:d4cc19a9 ARRAY /dev/md126 UUID=a8775c90:cee66376:5310fc13:63bcba5b ARRAY /dev/md125 UUID=b9a1149f:ae114fc8:a6000d77:354dc42a [root@localhost ~]# here is how /proc/mdstat looks like after I recreate the partition in the array so that it becomes available: [root@localhost ~]# cat /proc/mdstat Personalities : [raid1] md125 : active raid1 sdc[1] sdd[0] 976759808 blocks super external:/md127/0 [2/2] [UU] md127 : inactive sdc[1](S) sdd[0](S) 4514 blocks super external:imsm md126 : active raid1 sda[1] sdb[0] 312566784 blocks super external:/md1/0 [2/2] [UU] md1 : inactive sdb[1](S) sda[0](S) 4514 blocks super external:imsm unused devices: <none> [root@localhost ~]# Detailed output regarding the array in subject: [root@localhost ~]# mdadm --detail /dev/md125 /dev/md125: Container : /dev/md127, member 0 Raid Level : raid1 Array Size : 976759808 (931.51 GiB 1000.20 GB) Used Dev Size : 976759940 (931.51 GiB 1000.20 GB) Raid Devices : 2 Total Devices : 2 Update Time : Fri Jan 7 00:38:00 2011 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 UUID : 30ebc3c2:b6a64751:4758d05c:fa8ff782 Number Major Minor RaidDevice State 1 8 32 0 active sync /dev/sdc 0 8 48 1 active sync /dev/sdd [root@localhost ~]# and /etc/fstab, with /data commented (the filesystem that is on this array): # # /etc/fstab # Created by anaconda on Thu Jan 6 03:32:40 2011 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/mapper/vg00-rootlv / ext4 defaults 1 1 UUID=3d1b38a3-b469-4b7c-b016-8abfb26a5d7d /boot ext4 defaults 1 2 #UUID=420adfdd-6c4e-4552-93f0-2608938a4059 /data ext4 defaults 0 1 /dev/mapper/vg00-homelv /home ext4 defaults 1 2 /dev/mapper/vg00-tmplv /tmp ext4 defaults 1 2 /dev/mapper/vg00-varlv /var ext4 defaults 1 2 /dev/mapper/vg00-swaplv swap swap defaults 0 0 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 [root@localhost ~]# Thanks in advance to everyone that even read this whole issue :-)

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• multi_index composite_key replace with iterator

  - by Rohit

  Is there anyway to loop through an index in a boost::multi_index and perform a replace? #include <iostream> #include <string> #include <boost/multi_index_container.hpp> #include <boost/multi_index/composite_key.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> using namespace boost::multi_index; using namespace std; struct name_record { public: name_record(string given_name_,string family_name_,string other_name_) { given_name=given_name_; family_name=family_name_; other_name=other_name_; } string given_name; string family_name; string other_name; string get_name() const { return given_name + " " + family_name + " " + other_name; } void setnew(string chg) { given_name = given_name + chg; family_name = family_name + chg; } }; struct NameIndex{}; typedef multi_index_container< name_record, indexed_by< ordered_non_unique< tag<NameIndex>, composite_key < name_record, BOOST_MULTI_INDEX_MEMBER(name_record,string, name_record::given_name), BOOST_MULTI_INDEX_MEMBER(name_record,string, name_record::family_name) > > > > name_record_set; typedef boost::multi_index::index<name_record_set,NameIndex>::type::iterator IteratorType; typedef boost::multi_index::index<name_record_set,NameIndex>::type NameIndexType; void printContainer(name_record_set & ns) { cout << endl << "PrintContainer" << endl << "-------------" << endl; IteratorType it1 = ns.begin(); IteratorType it2 = ns.end (); while (it1 != it2) { cout<<it1->get_name()<<endl; it1++; } cout << "--------------" << endl << endl; } void modifyContainer(name_record_set & ns) { cout << endl << "ModifyContainer" << endl << "-------------" << endl; IteratorType it3; IteratorType it4; NameIndexType & idx1 = ns.get<NameIndex>(); IteratorType it1 = idx1.begin(); IteratorType it2 = idx1.end(); while (it1 != it2) { cout<<it1->get_name()<<endl; name_record nr = *it1; nr.setnew("_CHG"); bool res = idx1.replace(it1,nr); cout << "result is: " << res << endl; it1++; } cout << "--------------" << endl << endl; } int main() { name_record_set ns; ns.insert( name_record("Joe","Smith","ENTRY1") ); ns.insert( name_record("Robert","Brown","ENTRY2") ); ns.insert( name_record("Robert","Nightingale","ENTRY3") ); ns.insert( name_record("Marc","Tuxedo","ENTRY4") ); printContainer (ns); modifyContainer (ns); printContainer (ns); return 0; } PrintContainer ------------- Joe Smith ENTRY1 Marc Tuxedo ENTRY4 Robert Brown ENTRY2 Robert Nightingale ENTRY3 -------------- ModifyContainer ------------- Joe Smith ENTRY1 result is: 1 Marc Tuxedo ENTRY4 result is: 1 Robert Brown ENTRY2 result is: 1 -------------- PrintContainer ------------- Joe_CHG Smith_CHG ENTRY1 Marc_CHG Tuxedo_CHG ENTRY4 Robert Nightingale ENTRY3 Robert_CHG Brown_CHG ENTRY2 --------------

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• Why does PHP overwrite values when I iterate through this array twice (by reference, by value)

  - by jeremy

  If I iterate through an array twice, once by reference and then by value, PHP will overwrite the last value in the array if I use the same variable name for each loop. This is best illustrated through an example: $array = range(1,5); foreach($array as &$element) { $element *= 2; } print_r($array); foreach($array as $element) { } print_r($array); Output: Array ( [0] = 2 [1] = 4 [2] = 6 [3] = 8 [4] = 10 ) Array ( [0] = 2 [1] = 4 [2] = 6 [3] = 8 [4] = 8 ) Note that I am not looking for a fix, I am looking to understand why this is happening. Also note that it does not happen if the variable names in each loop are not each called $element, so I'm guessing it has to do with $element still being in scope and a reference after the end of the first loop.

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• How to search array for duplicates using a single array?

  - by patrick

  I am checking a list of 10 spots, each spot w/ 3 top users to see if a user is in an array before echoing and storing. foreach($top_10['top_10'] as $top10) //loop each spot { $getuser = ltrim($top10['url'], " users/" ); //strip url if ($usercount < 3) { if ((array_search($getuser, $array) !== true)) { echo $getuser; $array[$c++] = $getuser; } else { echo "duplicate <br /><br />"; } } } The problem I am having is that for every loop, it creates a multi-dimensional array for some reason which only allows array_search to search the current array and not all combined. I am wanting to store everything in the same $array. This is what I see after a print_r($array) Array ( [0] => 120728 [1] => 205247 ) Array ( [0] => 232123 [1] => 091928 )

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• Create new Array of parameter type

  - by pimvdb

  I'm trying to create a function to parse out all values in a multidimensional Array with all but one dimension given. The details are not relevant, but for this function I need to return an one-dimensional Array containing values of the same type the original multidimensional Array has. To pass any Array with any dimension to my function, I declared the type of this parameter as Array. However, how would I create a new Array of that specific type (e.g. Integer)? Currently I have the following code: Function GetRow(ByVal arr As Array) As Array Dim result As (...) 'This should be Integer() if arr contains Integers, etc. Return result End Function How do I declare the type of result to make it having the same type of values as arr? New Array is not possible as it is declared MustInherit. Thanks a lot.

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• Rebuilding array on 3ware 9690SA-8I

  - by Tim Jones

  I have a RAID10 (8x1TB) array on a 3ware 9690 card running on an Ubuntu 1110 server. There was a kernel update so I scheduled a reboot after which the array was inaccessible. I checked the status a drive has died in the array, but the controller has thrown the entire array into an 'inoperable' state instead of simply degraded (what's the point of the RAID now ;-). After taking out the 'dead' drive I run a quick test to find it completely functional without a bad sector to be found. I try to put the drive back in but the array still marks the disk as degraded (remembering serial number or something??) and the entire array as inoperable... So I swap it out for a known working drive (not the same capacity but higher - should still work) and initiate a rebuild with the the new drive as a replacement. This fails instantly with the error "(0x0B:0x0033): Unit busy : Failed to start Rebuild on Unit 0". The unit shouldn't be busy as it is not mounted (the card itself is listed with lshw but the array it provides is not). I'm pretty much at an impasse now, I don't understand how I can have a single drive failure on a RAID10 that makes the entire array inaccessible, degraded I could understand but inaccessible?? I don't think the controller as prior to the reboot it was completely functional.

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• Class member functions instantiated by traits

  - by Jive Dadson

  I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched Stack Overflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state information was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (VC++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice? UPDATE: Here's another try at explaining it. I want the user to be able to fill out an order (manifest) for a custom optimizer, something like ordering off of a Chinese menu - one from column A, one from column B, etc.. Waiter, from column A (updaters), I'll have the BFGS update with Cholesky-decompositon sauce. From column B (line-searchers), I'll have the cubic interpolation line-search with an eta of 0.4 and a rho of 1e-4, please. Etc... UPDATE: Okay, okay. Here's the playing-around that I've done. I offer it reluctantly, because I suspect it's a completely wrong-headed approach. It runs okay under vc++ 2008. #include <boost/utility.hpp> #include <boost/type_traits/integral_constant.hpp> namespace dj { struct CBFGS { void bar() {printf("CBFGS::bar %d\n", data);} CBFGS(): data(1234){} int data; }; template<class T> struct is_CBFGS: boost::false_type{}; template<> struct is_CBFGS<CBFGS>: boost::true_type{}; struct LMQN {LMQN(): data(54.321){} void bar() {printf("LMQN::bar %lf\n", data);} double data; }; template<class T> struct is_LMQN: boost::false_type{}; template<> struct is_LMQN<LMQN> : boost::true_type{}; struct default_optimizer_traits { typedef CBFGS update_type; }; template<class traits> class Optimizer; template<class traits> void foo(typename boost::enable_if<is_LMQN<typename traits::update_type>, Optimizer<traits> >::type& self) { printf(" LMQN %lf\n", self.data); } template<class traits> void foo(typename boost::enable_if<is_CBFGS<typename traits::update_type>, Optimizer<traits> >::type& self) { printf("CBFGS %d\n", self.data); } template<class traits = default_optimizer_traits> class Optimizer{ friend typename traits::update_type; //friend void dj::foo<traits>(typename Optimizer<traits> & self); // How? public: //void foo(void); // How??? void foo() { dj::foo<traits>(*this); } void bar() { data.bar(); } //protected: // How? typedef typename traits::update_type update_type; update_type data; }; } // namespace dj int main_() { dj::Optimizer<> opt; opt.foo(); opt.bar(); std::getchar(); return 0; }

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• using a Singleton to pass credentials in a multi-tenant application a code smell?

  - by Hans Gruber

  Currently working on a multi-tenant application that employs Shared DB/Shared Schema approach. IOW, we enforce tenant data segregation by defining a TenantID column on all tables. By convention, all SQL reads/writes must include a Where TenantID = '?' clause. Not an ideal solution, but hindsight is 20/20. Anyway, since virtually every page/workflow in our app must display tenant specific data, I made the (poor) decision at the project's outset to employ a Singleton to encapsulate the current user credentials (i.e. TenantID and UserID). My thinking at the time was that I didn't want to add a TenantID parameter to each and every method signature in my Data layer. Here's what the basic pseudo-code looks like: public class UserIdentity { public UserIdentity(int tenantID, int userID) { TenantID = tenantID; UserID = userID; } public int TenantID { get; private set; } public int UserID { get; private set; } } public class AuthenticationModule : IHttpModule { public void Init(HttpApplication context) { context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest); } private void context_AuthenticateRequest(object sender, EventArgs e) { var userIdentity = _authenticationService.AuthenticateUser(sender); if (userIdentity == null) { //authentication failed, so redirect to login page, etc } else { //put the userIdentity into the HttpContext object so that //its only valid for the lifetime of a single request HttpContext.Current.Items["UserIdentity"] = userIdentity; } } } public static class CurrentUser { public static UserIdentity Instance { get { return HttpContext.Current.Items["UserIdentity"]; } } } public class WidgetRepository: IWidgetRepository{ public IEnumerable<Widget> ListWidgets(){ var tenantId = CurrentUser.Instance.TenantID; //call sproc with tenantId parameter } } As you can see, there are several code smells here. This is a singleton, so it's already not unit test friendly. On top of that you have a very tight-coupling between CurrentUser and the HttpContext object. By extension, this also means that I have a reference to System.Web in my Data layer (shudder). I want to pay down some technical debt this sprint by getting rid of this singleton for the reasons mentioned above. I have a few thoughts on what an better implementation might be, but if anyone has any guidance or lessons learned they could share, I would be much obliged.

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• What is the best approach in SQL to store multi-level descriptions?

  - by gime

  I need a new perspective on how to design a reliable and efficient SQL database to store multi-level arrays of data. This problem applies to many situations but I came up with this example: There are hundreds of products. Each product has an undefined number of parts. Each part is built from several elements. All products are described in the same way. All parts would require the same fields to describe them (let's say: price, weight, part name), all elements of all parts also have uniform design (for example: element code, manufacturer). Plain and simple. One element may be related to only part, and each part is related to one product only. I came up with idea of three tables: Products: -------------------------------------------- prod_id prod_name prod_price prod_desc 1 hoover 120 unused next Parts: ---------------------------------------------------- part_id part_name part_price part_weight prod_id 3 engine 10 20 1 and finally Elements: --------------------------------------- el_id el_code el_manufacturer part_id 1 BFG12 GE 3 Now, select a desired product, select all from PARTS where prod_id is the same, and then select all from ELEMENTS where part_id matches - after multiple queries you've got all data. I'm just not sure if this is the right approach. I've got also another idea, without ELEMENTS table. That would decrease queries but I'm a bit afraid it might be lame and bad practice. Instead of ELEMENTS table there are two more fields in the PARTS table, so it looks like this: part_id, part_name, part_price, part_weight, prod_id, part_el_code, part_el_manufacturer they would be text type, and for each part, information about elements would be stored as strings, this way: part_el_code | code_of_element1; code_of_element2; code_of_element3 part_el_manufacturer | manuf_of_element1; manuf_of_element2; manuf_of_element3 Then all we need is to explode() data from those fields, and we get arrays, easy to display. Of course this is not perfect and has some limitations, but is this idea ok? Or should I just go with the first idea? Or maybe there is a better approach to this problem? It's really hard to describe it in few words, and that means it's hard to search for answer. Also, understanding the principles of designing databases is not that easy as it seems.

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• Tile engine Texture not updating when numbers in array change

  - by Corey

  I draw my map from a txt file. I am using java with slick2d library. When I print the array the number changes in the array, but the texture doesn't change. public class Tiles { public Image[] tiles = new Image[5]; public int[][] map = new int[64][64]; public Image grass, dirt, fence, mound; private SpriteSheet tileSheet; public int tileWidth = 32; public int tileHeight = 32; public void init() throws IOException, SlickException { tileSheet = new SpriteSheet("assets/tiles.png", tileWidth, tileHeight); grass = tileSheet.getSprite(0, 0); dirt = tileSheet.getSprite(7, 7); fence = tileSheet.getSprite(2, 0); mound = tileSheet.getSprite(2, 6); tiles[0] = grass; tiles[1] = dirt; tiles[2] = fence; tiles[3] = mound; int x=0, y=0; BufferedReader in = new BufferedReader(new FileReader("assets/map.dat")); String line; while ((line = in.readLine()) != null) { String[] values = line.split(","); x = 0; for (String str : values) { int str_int = Integer.parseInt(str); map[x][y]=str_int; //System.out.print(map[x][y] + " "); x++; } //System.out.println(""); y++; } in.close(); } public void update(GameContainer gc) { } public void render(GameContainer gc) { for(int y = 0; y < map.length; y++) { for(int x = 0; x < map[0].length; x ++) { int textureIndex = map[x][y]; Image texture = tiles[textureIndex]; texture.draw(x*tileWidth,y*tileHeight); } } } } Mouse Picking Where I change the number in the array Input input = gc.getInput(); gc.getInput().setOffset(cameraX-400, cameraY-300); float mouseX = input.getMouseX(); float mouseY = input.getMouseY(); double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { System.out.println("Clicked"); if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } I never ask a question until I have tried to figure it out myself. I have been stuck with this problem for two weeks. It's not like this site is made for asking questions or anything. So if you actually try to help me instead of telling me to use a debugger thank you. You either get told you have too much or too little code. Nothing is never enough for the people on here it's as bad as something like reddit. Idk what is wrong all my textures work when I render them it just doesn't update when the number in the array changes. I am obviously debugging when I say that I was printing the array and the number is changing like it should, so it's not a problem with my mouse picking code. It is a problem with my textures, but I don't know what because they all render correctly. That is why I need help.

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• Can't install chef, gem version conflict with net-ssh net-ssh-multi net-ssh-gateway

  - by Mojo

  Using rvm, and an empty gemset, I get this: $ gem install chef --no-ri --no-rdoc ERROR: While executing gem ... (Gem::DependencyError) Unable to resolve dependencies: chef requires net-ssh (~> 2.2.2); net-ssh-multi requires net-ssh (>= 2.6.5); net-ssh-gateway requires net-ssh (>= 2.6.5) I've tried resolving it by installing earlier versions of net-ssh-gateway and net-ssh-multi, but net-ssh-multi version 1.1 confounds me by installing 1.1.2.

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