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  • How detect length of a numpy array with only one element?

    - by mishaF
    I am reading in a file using numpy.genfromtxt which brings in columns of both strings and numeric values. One thing I need to do is detect the length of the input. This is all fine provided there are more than one value read into each array. But...if there is only one element in the resulting array, the logic fails. I can recreate an example here: import numpy as np a = np.array(2.3) len(a) returns an error saying: TypeError: len() of unsized object however, If a has 2 or more elements, len() behaves as one would expect. import numpy as np a = np.array([2.3,3.6]) len(a) returns 2 My concern here is, if I use some strange exception handling, I can't distinguish between a being empty and a having length = 1.

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  • What is the difference between check and foreign key?

    - by GigaPr
    Hi, i am quite confused about the difference between a FOREIGN KEY and CHECK constraint. they appear to me to achieve the same result. I mean I could create a table and enforce a Foreign key on another table, but i could create a CHECK to ensure the value in in another table. What is the difference and when to use the one or the other? thanks

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  • JavaScript: Is there a better way to retain your array but efficiently concat or replace items?

    - by Michael Mikowski
    I am looking for the best way to replace or add to elements of an array without deleting the original reference. Here is the set up: var a = [], b = [], c, i, obj; for ( i = 0; i < 100000; i++ ) { a[ i ] = i; b[ i ] = 10000 - i; } obj.data_list = a; Now we want to concatenate b INTO a without changing the reference to a, since it is used in obj.data_list. Here is one method: for ( i = 0; i < b.length; i++ ) { a.push( b[ i ] ); } This seems to be a somewhat terser and 8x (on V8) faster method: a.splice.apply( a, [ a.length, 0 ].concat( b ) ); I have found this useful when iterating over an "in-place" array and don't want to touch the elements as I go (a good practice). I start a new array (let's call it keep_list) with the initial arguments and then add the elements I wish to retain. Finally I use this apply method to quickly replace the truncated array: var keep_list = [ 0, 0 ]; for ( i = 0; i < a.length; i++ ){ if ( some_condition ){ keep_list.push( a[ i ] ); } // truncate array a.length = 0; // And replace contents a.splice.apply( a, keep_list ); There are a few problems with this solution: there is a max call stack size limit of around 50k on V8 I have not tested on other JS engines yet. This solution is a bit cryptic Has anyone found a better way?

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  • Which of these Array Initializations is better in Ruby?

    - by Bragaadeesh
    Hi, Which of these two forms of Array Initialization is better in Ruby? Method 1: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = Array.new(DAYS_IN_A_WEEK.size).map!{ Array.new(HOURS_IN_A_DAY.size) } DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day][hour] = 'something' end end Method 2: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = {} DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day] ||= {} @data[day][hour] = 'something' end end The difference between the first method and the second method is that the second one does not allocate memory initially. I feel the second one is a bit inferior when it comes to performance due to the numerous amount of Array copies that has to happen. However, it is not straight forward in Ruby to find what is happening. So, if someone can explain me which is better, it would be really great! Thanks

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  • Difference between name != null and null != name in java?

    - by GK
    I have seen people using the following conditions interchangeably. String name; //some code if(name != null) //or if(null != name) So is there any difference in this? or both are same? I am asking this here because, i heard that there is some difference in these, but don't know what. Thanks

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  • php: possible to convert array of numbers to 'from' and 'to' pairs where consecutive?

    - by Haroldo
    I have an array of timestamps referring to the days when a holiday home is booked. each timestamp is a round day. I want to turn this into an array of 'begins' and 'ends' pairs for consecutive dates Are there any php functions I should be aware of for writing this function? Or does anyone have any pointers for this kind of thing? thanks! edit: example array: Array ( [0] => 1273536000 [1] => 1273622400 [2] => 1273708800 [3] => 1273795200 [4] => 1273881600 [5] => 1273968000 [6] => 1274054400 [7] => 1274140800 [8] => 1274227200 ) where a day = 86400 (seconds)

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  • What's the best way to have functions share an array in Objective-C?

    - by editor
    I understand that in Objective-C you declare an array in the header file and interact with it in a class. So far I'm adding things and fetching them fine within a single function. I'm new to the language however and can't figure out how to share that array across other functions. I'd like to initialize array data in my viewDidLoad and access it from various functions later on. Is this possible and if so what's the best way to do it?

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  • JavaScript: String Concatenation slow performance? Array.join('')?

    - by NickNick
    I've read that if I have a for loop, I should not use string concation because it's slow. Such as: for (i=0;i<10000000;i++) { str += 'a'; } And instead, I should use Array.join(), since it's much faster: var tmp = []; for (i=0;i<10000000;i++) { tmp.push('a'); } var str = tmp.join(''); However, I have also read that string concatention is ONLY a problem for Internet Explorer and that browsers such as Safari/Chrome, which use Webkit, actually perform FASTER is using string concatention than Array.join(). I've attempting to find a performance comparison between all major browser of string concatenation vs Array.join() and haven't been able to find one. As such, what is faster and more efficient JavaScript code? Using string concatenation or Array.join()?

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  • Drupal: Create custom search

    - by Dr. Hfuhruhurr
    I'm trying to create a custom search but getting stuck. What I want is to have a dropdownbox so the user can choose where to search in. These options can mean 1 or more content types. So if he chooses options A, then the search will look in node-type P,Q,R. But he may not give those results, but only the uid's which will be then themed to gather specific data for that user. To make it a little bit clearer, Suppose I want to llok for people. The what I'm searching in is 2 content profile types. But ofcourse you dont want to display those as a result, but a nice picture of the user and some data. I started with creating a form with a textfield and the dropdown box. Then, in the submit handler, i created the keys and redirected to another pages with those keys as a tail. This page has been defined in the menu hook, just like how search does it. After that I want to call hook_view to do the actual search by calling node_search, and give back the results. Unfortunately, it goes wrong. When i click the Search button, it gives me a 404. But am I on the right track? Is this the way to create a custom search? Thx for your help. Here's the code for some clarity: <?php // $Id$ /* * @file * Searches on Project, Person, Portfolio or Group. */ /** * returns an array of menu items * @return array of menu items */ function vm_search_menu() { $subjects = _vm_search_get_subjects(); foreach ($subjects as $name => $description) { $items['zoek/'. $name .'/%menu_tail'] = array( 'page callback' => 'vm_search_view', 'page arguments' => array($name), 'type' => MENU_LOCAL_TASK, ); } return $items; } /** * create a block to put the form into. * @param $op * @param $delta * @param $edit * @return mixed */ function vm_search_block($op = 'list', $delta = 0, $edit = array()) { switch ($op) { case 'list': $blocks[0]['info'] = t('Algemene zoek'); return $blocks; case 'view': if (0 == $delta) { $block['subject'] = t(''); $block['content'] = drupal_get_form('vm_search_general_form'); } return $block; } } /** * Define the form. */ function vm_search_general_form() { $subjects = _vm_search_get_subjects(); foreach ($subjects as $key => $subject) { $options[$key] = $subject['desc']; } $form['subjects'] = array( '#type' => 'select', '#options' => $options, '#required' => TRUE, ); $form['keys'] = array( '#type' => 'textfield', '#required' => TRUE, ); $form['submit'] = array( '#type' => 'submit', '#value' => t('Zoek'), ); return $form; } function vm_search_general_form_submit($form, &$form_state) { $subjects = _vm_search_get_subjects(); $keys = $form_state['values']['keys']; //the search keys //the content types to search in $keys .= ' type:' . implode(',', $subjects[$form_state['values']['subjects']]['types']); //redirect to the page, where vm_search_view will handle the actual search $form_state['redirect'] = 'zoek/'. $form_state['values']['subjects'] .'/'. $keys; } /** * Menu callback; presents the search results. */ function vm_search_view($type = 'node') { // Search form submits with POST but redirects to GET. This way we can keep // the search query URL clean as a whistle: // search/type/keyword+keyword if (!isset($_POST['form_id'])) { if ($type == '') { // Note: search/node can not be a default tab because it would take on the // path of its parent (search). It would prevent remembering keywords when // switching tabs. This is why we drupal_goto to it from the parent instead. drupal_goto($front_page); } $keys = search_get_keys(); // Only perform search if there is non-whitespace search term: $results = ''; if (trim($keys)) { // Log the search keys: watchdog('vm_search', '%keys (@type).', array('%keys' => $keys, '@type' => $type)); // Collect the search results: $results = node_search('search', $type); if ($results) { $results = theme('box', t('Zoek resultaten'), $results); } else { $results = theme('box', t('Je zoek heeft geen resultaten opgeleverd.')); } } } return $results; } /** * returns array where to look for * @return array */ function _vm_search_get_subjects() { $subjects['opdracht'] = array('desc' => t('Opdracht'), 'types' => array('project') ); $subjects['persoon'] = array('desc' => t('Persoon'), 'types' => array('types_specialisatie', 'smaak_en_interesses') ); $subjects['groep'] = array('desc' => t('Groep'), 'types' => array('Villamedia_groep') ); $subjects['portfolio'] = array('desc' => t('Portfolio'), 'types' => array('artikel') ); return $subjects; }

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  • Possible to migrate from non-RAID to RAID 1 and then RAID 5?

    - by stueng
    Using software RAID only Is it possible to start with a 2TB disk full of data and safely add it to a RAID 1 array? Is it then possible to add a third disk and migrate the RAID 1 array into a RAID 5 array? OR Is it possible to start with a 2 disk degraded RAID 5 array and then add the third disk later to create a health RAID 5 array? Backstory: I wish to migrate from a 2 disk NAS (RAID 1) to a 3 disk NAS and only purchase one new disk in doing so

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  • is it good to have or difference between ADSL Modem+WiFi Router and Separate ADSL Modem & Wi-Fi Router?

    - by vikas devde
    I have ADSL2 Modem which I got from my service provider, now I want to setup wireless(Wi-Fi) in my home. I went to shop, where I came to know that there are routers which come up with modem also but they are priced lil higher than the only wi-fi routers. Now it is obvious that I should go for only wi-fi one, as I already have modem. My question is, is there any difference between ADSL+router and only router? I think if I use ADSL+router, the speed will increase lilbit, as modem does modulate and demodulate signals, and router also generates wireless signal, that is time to take conversions is doubled, and if I use ADSL+modem, it will directly convert the signals to wireless, and time will be saved, so the overall speed will increase lilbit. This is what my concept is(Which might be wrong). What do you guys would suggest me? should I take my current modem away and buy an ADSL+router or I should keep my modem and buy only wi-fi one. Please tell me the difference and suggest me which one I should go with, and also suggest me which company router I should go for.

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  • What is the difference between the Linux and Linux LVM partition type?

    - by ujjain
    Fdisk shows multiple partition types. What is the difference between choosing 83) Linux and 8e) Linux LVM? Choosing 83) Linux also works fine for using LVM, even creating a physical volume on /dev/sdb without a partition table works. Does picking a partition type in fdisk really matter? What is the difference in picking Linux or Linux LVM as partition type? [root@tst-01 ~]# fdisk /dev/sdb WARNING: DOS-compatible mode is deprecated. It's strongly recommended to switch off the mode (command 'c') and change display units to sectors (command 'u'). Command (m for help): l 0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris 1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT- 2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT- 3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT- 4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx 5 Extended 42 SFS 86 NTFS volume set da Non-FS data 6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / . 7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility 8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt 9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/ 10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b 11 Hidden FAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor 12 Compaq diagnost 61 SpeedStor a9 NetBSD f4 SpeedStor 14 Hidden FAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary 16 Hidden FAT16 64 Novell Netware af HFS / HFS+ fb VMware VMFS 17 Hidden HPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE 18 AST SmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto 1b Hidden W95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep 1c Hidden W95 FAT3 80 Old Minix be Solaris boot ff BBT 1e Hidden W95 FAT1 Command (m for help):

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  • Difference between all servers in one cluster and more than one cluster with servers?

    - by silla
    Not sure I understand what´s the difference or how it works when servers a running in one cluster or if there are more than one clusters with servers in it - regard High availability & Load Balancing. For me they are somehow the same, there is not really a big difference. Let´s make a simple example: 2 Servers in 1 Cluster 2 Clusters with each 1 Server - 1. If one Server failure, the other one is able to continue the work. The same for Load Balancing, these two Servers are able to balance the work together. - 2. The same thing! If one Server failure... The only thing that could be a problem with point 1. is if the Cluster fails (then both of the Server are dead). But is this even possible? I was reading stuff about clustering and high availability but I think I do not get this really. Probably I did not really understand how a cluster is working. Are these 2 points with 1 Cluster and 2 Clusters somehow the same or are there really some big differences? What should I know about it? Thank you

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  • Initialize array in amortized constant time -- what is this trick called?

    - by user946850
    There is this data structure that trades performance of array access against the need to iterate over it when clearing it. You keep a generation counter with each entry, and also a global generation counter. The "clear" operation increases the generation counter. On each access, you compare local vs. global generation counters; if they differ, the value is treated as "clean". This has come up in this answer on Stack Overflow recently, but I don't remember if this trick has an official name. Does it? One use case is Dijkstra's algorithm if only a tiny subset of the nodes has to be relaxed, and if this has to be done repeatedly.

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  • Removing/Adding a specific variable from an object inside javascript array? [migrated]

    - by hustlerinc
    I have a map array with objects stuffed with variables looking like this: var map = [ [{ground:0, object:1}, {ground:0, item:2}, {ground:0, object:1, item:2}], [{ground:0, object:1}, {ground:0, item:2}, {ground:0, object:1, item:2}] ]; Now I would like to be able to delete and add one of the variables like item:2. 1) What would I use to delete specific variables? 2) What would I use to add specific variables? I just need 2 short lines of code, the rest like detecting if and where to execute I've figured out. I've tried delete map[i][j].item; with no results. Help appreciated.

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  • How can i assign a two dimensional array into other temporary two dimensional array.....?? in C Programming..

    - by AGeek
    Hi I am trying to store the contents of two dimensional array into a temporary array.... How is it possible... I don't want looping over here, as it would add an extra overhead.. Any pointer notation would be good. struct bucket { int nStrings; char strings[MAXSTRINGS][MAXWORDLENGTH]; }; void func() { char **tArray; int tLenArray = 0; for(i=0; i<TOTBUCKETS-1; i++) { if(buck[i].nStrings != 0) { tArray = buck[i].strings; tLenArray = buck[i].nStrings; } } } The error here i am getting is:- [others@centos htdocs]$ gcc lexorder.c lexorder.c: In function âlexSortingâ: lexorder.c:40: warning: assignment from incompatible pointer type Please let me know if this needs some more explanaition...

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  • Finding out the common / uncommon elements between two Arrays in PHP

    - by Veera
    Consider I have two arrays: $friends = Array('foo', 'bar', 'alpha'); $attendees = Array('foo', 'bar'); Now I need to populate a new array $nonattendees which contains only the elements which are in $friends array and not in $attendees array. i.e, $nonattendees array should be populated with 'alpha'. Is there any in built array operation available in PHP to achieve the above functionality or should I write my own for loops?

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  • What is the difference between calling Stream.Write and using a StreamWriter?

    - by John Nelson
    What is the difference between instantiating a Stream object, such as MemoryStream and calling the memoryStream.Write() method to write to the stream, and instantiating a StreamWriter object with the stream and calling streamWriter.Write()? Consider the following scenario: You have a method that takes a Stream, writes a value, and returns it. The stream is read from later on, so the position must be reset. There are two possible ways of doing it (both seem to work). // Instantiate a MemoryStream somewhere // - Passed to the following two methods MemoryStream memoryStream = new MemoryStream(); // Not using a StreamWriter private static Stream WriteToStream(Stream stream, string value) { stream.Write(Encoding.Default.GetBytes(value), 0, value.Length); stream.Flush(); stream.Position = 0; return stream; } // Using a StreamWriter private static Stream WriteToStreamWithWriter(Stream stream, string value) { StreamWriter sw = new StreamWriter(stream); sw.Write(value, 0, value.Length); sw.Flush(); stream.Position = 0; return stream; } This is partially a scope problem, as I don't want to close the stream after writing to it since it will be read from later. I also certainly don't want to dispose it either, because that will close my stream. The difference seems to be that not using a StreamWriter introduces a direct dependency on Encoding.Default, but I'm not sure that's a very big deal. What's the difference, if any?

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  • What is the difference between a desktop environment and a window manager?

    - by Zolomon
    As the title says. I'm having a really hard time trying to understand what the differences between a desktop environment and a window manager are? EDIT: This is what I found out later. There are basically three layers that can be included in the Linux desktop: X Windows – This is the foundation that allows for graphic elements to be drawn on the display. X Windows builds the primitive framework that allows moving of windows, interactions with keyboard and mouse, and draws windows. This is required for any graphical desktop. Window Manager – The Window Manager is the piece of the puzzle that controls the placement and appearance of windows. Window Managers include: Enlightenment, Afterstep, FVWM, Fluxbox, IceWM, etc. Requires X Windows but not a desktop environment. Desktop Environment – This is where it begins to get a little fuzzy for some. A Desktop Environment includes a Window Manager but builds upon it. The Desktop Environment typically is a far more fully integrated system than a Window Manager. Requires both X Windows and a Window Manager.

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  • The Difference Between .com, .net, .org and Why We’re About To See Many More Top-Level Domains

    - by Chris Hoffman
    .com, .net, .org and other website suffixes are known as “top-level domains” (TLDs). While we normally see only a few of these, there are hundreds of them – and there may be thousands more soon. Top-level domains are managed by the Internet Assigned Numbers Authority (IANA), which is run by the Internet Corporation for Assigned Names and Numbers (ICANN). HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference How To Troubleshoot Internet Connection Problems

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