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  • Rails 3 - Nested layouts - LocalJumpError

    - by Art Shayderov
    Hi Nested layouts do not work in Rails 3. After I hit this I tried Rails Guides Example on a blank project (both ruby 1.9.1 and 1.8.7). LocalJumpError no block given on line <%= yield :stylesheets %. If you remove this line you will get the same error on the next yield statement. Could someone fix(patch) this? It's probably just a matter of calling block_given? in the right place. That would be great. Thanks Added on 4/3: Rails 3 beta 2 released. Problem fixed.

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  • Complex behavior generated by simple computation

    - by Yuval A
    Stephen Wolfram gave a fascinating talk at TED about his work with Mathematica and Wolfram Alpha. Amongst other things, he pointed out how very simple computations can yield extremely complex behaviors. (He goes on to discuss his ambition for computing the entire physical universe. Say what you will, you gotta give the guy some credit for his wild ideas...) As an example he showed several cellular automata. What other examples of simple computations do you know of that yield fascinating results?

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  • How do I check if a user is authenticated with NickServ using POE::Component::IRC::State in Perl?

    - by Troy
    I'm trying to test whether a user is registered on FreeNode. nick_info() doesn't seem to return information about this, so I want to use $irc-yield(whois = $nick); and then grab the irc_whois event's reply. The problem is that I want to wait until this event is fired, so I created a global variable $whois_result and wrote a sub like this: sub whois { my $nick = $_[0]; $whois_result = 0; $irc->yield(whois => $nick); while($whois_result == 0) { } return $whois_result; } with the irc_whois handler looking like: sub on_whois { $whois_result = $_[ARG0]; print "DEBUG: irc_whois fired.\n"; } Unfortunately, the event can't fire while the loop is running so this hangs. I'm sure there's a better way to do this, but I'm not familiar enough with this kind of programming to know. Any help would be greatly appreciated.

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  • What does Ruby have that Python doesn't, and vice versa?

    - by Lennart Regebro
    There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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  • Combinations and Permutations in F#

    - by Noldorin
    I've recently written the following combinations and permutations functions for an F# project, but I'm quite aware they're far from optimised. /// Rotates a list by one place forward. let rotate lst = List.tail lst @ [List.head lst] /// Gets all rotations of a list. let getRotations lst = let rec getAll lst i = if i = 0 then [] else lst :: (getAll (rotate lst) (i - 1)) getAll lst (List.length lst) /// Gets all permutations (without repetition) of specified length from a list. let rec getPerms n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> getRotations |> Seq.collect (fun r -> Seq.map ((@) [List.head r]) (getPerms (k - 1) (List.tail r))) /// Gets all permutations (with repetition) of specified length from a list. let rec getPermsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> Seq.collect (fun x -> Seq.map ((@) [x]) (getPermsWithRep (k - 1) lst)) // equivalent: | k, _ -> lst |> getRotations |> Seq.collect (fun r -> List.map ((@) [List.head r]) (getPermsWithRep (k - 1) r)) /// Gets all combinations (without repetition) of specified length from a list. let rec getCombs n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombs (k - 1) xs)) (getCombs k xs) /// Gets all combinations (with repetition) of specified length from a list. let rec getCombsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombsWithRep (k - 1) lst)) (getCombsWithRep k xs) Does anyone have any suggestions for how these functions (algorithms) can be sped up? I'm particularly interested in how the permutation (with and without repetition) ones can be improved. The business involving rotations of lists doesn't look too efficient to me in retrospect. Update Here's my new implementation for the getPerms function, inspired by Tomas's answer. Unfortunately, it's not really any fast than the existing one. Suggestions? let getPerms n lst = let rec getPermsImpl acc n lst = seq { match n, lst with | k, x :: xs -> if k > 0 then for r in getRotations lst do yield! getPermsImpl (List.head r :: acc) (k - 1) (List.tail r) if k >= 0 then yield! getPermsImpl acc k [] | 0, [] -> yield acc | _, [] -> () } getPermsImpl List.empty n lst

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  • Which are your favorite programming language gadgets?

    - by FerranB
    There are some gadgets/features for programming languages that I like a lot because they save a lot of coding or simply because they are magical or nice. Some of my favorites are: C++ increment/decrement operator: my_array[++c]; C++ assign and sum or substract (...): a += b C# yield return: yield return 1; C# foreach: foreach (MyClass x in MyCollection) PLSQL for loop: for c in (select col1, col2 from mytable) PLSQL pipe row: for i in 1..x loop pipe row(i); end loop; Python Array access operator: a[:1] PLSQL ref cursors. Which are yours?

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  • how to change string values in dictionary to int values

    - by tom smith
    I have a dictionary such as: {'Sun': {'Satellites': 'Mercury,Venus,Earth,Mars,Jupiter,Saturn,Uranus,Neptune,Ceres,Pluto,Haumea,Makemake,Eris', 'Orbital Radius': '0', 'Object': 'Sun', 'RootObject': 'Sun', 'Radius': '20890260'}, 'Earth': {'Period': '365.256363004', 'Satellites': 'Moon', 'Orbital Radius': '77098290', 'Radius': '63710.41000.0', 'Object': 'Earth'}, 'Moon': {'Period': '27.321582', 'Orbital Radius': '18128500', 'Radius': '1737000.10', 'Object': 'Moon'}} I am wondering how to change just the number values to ints instead of strings. def read_next_object(file): obj = {} for line in file: if not line.strip(): continue line = line.strip() key, val = line.split(": ") if key in obj and key == "Object": yield obj obj = {} obj[key] = val yield obj planets = {} with open( "smallsolar.txt", 'r') as f: for obj in read_next_object(f): planets[obj["Object"]] = obj print(planets)

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  • Converting the value from string to integer in a nested dictionary

    - by tom smith
    I want to change the numbers in my dictionary to int values for use later in my program. So far I have import time import math x = 400 y = 300 def read_next_object(file): obj = {} for line in file: if not line.strip(): continue line = line.strip() key, val = line.split(": ") if key in obj and key == "Object": yield obj obj = {} obj[key] = val yield obj planets = {} with open( "smallsolar.txt", 'r') as f: for obj in read_next_object(f): planets[obj["Object"]] = obj print(planets) scale=250/int(max([planets[x]["Orbital Radius"] for x in planets if "Orbital Radius" in planets[x]])) print(scale) and the output is {'Sun': {'Object': 'Sun', 'Satellites': 'Mercury,Venus,Earth,Mars,Jupiter,Saturn,Uranus,Neptune,Ceres,Pluto,Haumea,Makemake,Eris', 'Orbital Radius': '0', 'RootObject': 'Sun', 'Radius': '20890260'}, 'Moon': {'Object': 'Moon', 'Orbital Radius': '18128500', 'Period': '27.321582', 'Radius': '1737000.10'}, 'Earth': {'Object': 'Earth', 'Satellites': 'Moon', 'Orbital Radius': '77098290', 'Period': '365.256363004', 'Radius': '6371000.0'}} 3.2426140709476178e-06 I want to be able to convert the numbers in the dict to ints for further use. Any help in greatly appreciated.

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  • Rails Tutorial Chapter 4 2nd Ed. Title Helper not being called with out argument.

    - by SuddenlyAwakened
    I am running through the Rails Tutorial by Michael Hartl (Screen Cast). Ran into the and issue in chapter 4 on the title helper. I have been putting my own twist on the code as I go to make sure I understand it all. However on this one I it is very similar and I am not quite sure why it is acting the way it is. Here is the code: Application.html.erb <!DOCTYPE html> <html> <head> <%- Rails.logger.info("Testing: #{yield(:title)}") %> <title><%= full_title(yield(:title)) %></title> <%= stylesheet_link_tag "application", :media => "all" %> <%= javascript_include_tag "application" %> <%= csrf_meta_tags %> </head> <body> <%= yield %> </body> </html> Application_helper.rb module ApplicationHelper def full_title(page_title) full_title = "Ruby on Rails Tutorial App" full_title += " | #{page_title}" unless page_title.blank? end end Home.html.erb <h1><%= t(:sample_app) %></h1> <p> This is the home page for the <a href="http://railstutorial.org/">Ruby on Rails Tutorial</a> sample application </p> about.html.erb <% provide(:title, t(:about_us)) %> <h1><%= t(:about_us) %></h1> <p> The <a href="http://railstutorial.org/">Ruby on Rails Tutorial</a> is a project to make a book and screencast to teach web development with <a href="http://railstutorial.org/">Ruby on Rails</a>. This is the sample application for the tutorial. </p> What Happens: The code works fine when I set the provide method like on the about page. However when I do not it does not seem to even call the helper. I am assuming that because no title is passed back. Any ideas on what I am doing wrong? Thank you all for your help.

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  • Rails 3 beta 1 - Nested layouts - LocalJumpError

    - by Art Shayderov
    Hi Nested layouts do not work in Rails 3. After I hit this I tried Rails Guides Example on a blank project (both ruby 1.9.1 and 1.8.7). LocalJumpError no block given on line <%= yield :stylesheets %. If you remove this line you will get the same error on the next yield statement. Could someone fix(patch) this? It's probably just a matter of calling block_given? in the right place. That would be great. Thanks Added on 4/3: Rails 3 beta 2 released. Problem fixed.

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  • Determine if PowerShell function is running as part of a pipeline?

    - by Richard Cook
    Can a PowerShell function determine if it is being run as part of a pipeline? I have a function which populates an array with instances of FileInfo which I would like to "yield" to the pipeline if the function is being run this way or produce some pretty output if the function is being invoked by itself from the command line. function Do-Something { $file_infos = @() # Populate $file_infos with FileInfo instances... if (INVOKED_IN_PIPELINE) { return $file_infos } else { foreach ($file_info in $file_infos) { write-host -foregroundcolor yellow $file_info.fullname } } } Basically, I'm trying to figure out how to implement INVOKED_IN_PIPELINE. If it is run in a pipeline (e.g. Do-Something | format-table fullname), I would simply yield the array, but if run directly (e.g. Do-Something), it would simply pretty-print the output. Is there a way to do this? If there is a more "idiomatic" way to achieve this kind of thing, I would also be interested to know.

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  • itertools.product eliminating repeated reversed tuples

    - by genclik27
    I asked a question yesterday and thanks to Tim Peters, it is solved. The question is here; itertools.product eliminating repeated elements The new question is further version of this. This time I will generate tuples inside of tuples. Here is an example; lis = [[(1,2), (3,4)], [(5,2), (1,2)], [(2,1), (1,2)]] When I use it in itertools.product function this is what I get, ((1, 2), (5, 2), (2, 1)) ((1, 2), (5, 2), (1, 2)) ((1, 2), (1, 2), (2, 1)) ((1, 2), (1, 2), (1, 2)) ((3, 4), (5, 2), (2, 1)) ((3, 4), (5, 2), (1, 2)) ((3, 4), (1, 2), (2, 1)) ((3, 4), (1, 2), (1, 2)) I want to change it in a way that if a sequence has (a,b) inside of it, then it can not have (b,a). In this example if you look at this sequence ((3, 4), (1, 2), (2, 1)) it has (1,2) and (2,1) inside of it. So, this sequence ((3, 4), (1, 2), (2, 1)) should not be considered in the results. As I said, I asked similar question before, in that case it was not considering duplicate elements. I try to adapt it to my problem. Here is modified code. Changed parts in old version are taken in comments. def reverse_seq(seq): s = [] for i in range(len(seq)): s.append(seq[-i-1]) return tuple(s) def uprod(*seqs): def inner(i): if i == n: yield tuple(result) return for elt in sets[i] - reverse: #seen.add(elt) rvrs = reverse_seq(elt) reverse.add(rvrs) result[i] = elt for t in inner(i+1): yield t #seen.remove(elt) reverse.remove(rvrs) sets = [set(seq) for seq in seqs] n = len(sets) #seen = set() reverse = set() result = [None] * n for t in inner(0): yield t In my opinion this code should work but I am getting error for the input lis = [[(1,2), (3,4)], [(5,2), (1,2)], [(2,1), (1,2)]]. I could not understand where I am wrong. for i in uprod(*lis): print i Output is, ((1, 2), (1, 2), (1, 2)) Traceback (most recent call last): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 39, in <module> for i in uprod(*lis): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 32, in uprod for t in inner(0): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 22, in inner for t in inner(i+1): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 25, in inner reverse.remove(rvrs) KeyError: (2, 1) Thanks,

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  • View code inside Javascript file on Rails

    - by SpyrosP
    Hello, previously i had javascript code right in the top of my view and it would work. Then, i learned that you can include the js file using yield and i did just that. I had rails view code inside my javascript code like : $( "#exp-progressbar" ).progressbar({ value: <%= ((@quest.end_time - Time.now).to_i * 100 ) / (@quest.duration * 60) %> }); Now, after i do it with yield, i get an error when i do that in the separate js file. How can i do it now ?

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  • Multi join query returns to many results and improperly matched

    - by Woot4Moo
    I have the following minimal schema in Oracle: http://sqlfiddle.com/#!4/c1ed0/14 The queries I have run yield too many results and this query: select cat.*, status.*, source.* from cats cat, status status, source source Left OUTER JOIN source source2 on source2.sourceid = 1 Right OUTER JOIN status status2 on status2.isStray =0 order by cat.name will yield incorrect results. What I am expecting is a table that looks like the following however I cannot seem to come up with the correct SQL. NAME AGE LENGTH STATUSID CATSOURCE ISSTRAY SOURCEID CATID Adam 1 25 null null null 1 2 Bill 5 1 null null null null null Charles 7 5 null null null null null Steve 12 15 1 1 1 1 1 In plain English what I am looking for is to return all known cats + their associated cat source + their cat status while retaining null values. The only information I will have is the source that I am curious about. I also only want the cats that have a status of either STRAY or UNKNOWN (null)

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  • How to stream an HttpResponse with Django

    - by muudscope
    I'm trying to get the 'hello world' of streaming responses working for Django (1.2). I figured out how to use a generator and the yield function. But the response still not streaming. I suspect there's a middleware that's mucking with it -- maybe ETAG calculator? But I'm not sure how to disable it. Can somebody please help? Here's the "hello world" of streaming that I have so far: def stream_response(request): resp = HttpResponse( stream_response_generator()) return resp def stream_response_generator(): for x in range(1,11): yield "%s\n" % x # Returns a chunk of the response to the browser time.sleep(1)

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  • Can the lock function be used to implement thread-safe enumeration?

    - by Daniel
    I'm working on a thread-safe collection that uses Dictionary as a backing store. In C# you can do the following: private IEnumerable<KeyValuePair<K, V>> Enumerate() { if (_synchronize) { lock (_locker) { foreach (var entry in _dict) yield return entry; } } else { foreach (var entry in _dict) yield return entry; } } The only way I've found to do this in F# is using Monitor, e.g.: let enumerate() = if synchronize then seq { System.Threading.Monitor.Enter(locker) try for entry in dict -> entry finally System.Threading.Monitor.Exit(locker) } else seq { for entry in dict -> entry } Can this be done using the lock function? Or, is there a better way to do this in general? I don't think returning a copy of the collection for iteration will work because I need absolute synchronization.

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  • Permutations in python 2.5.2

    - by flpgdt
    Hi, I have a list of numbers for input, e.g. 671.00 1,636.00 436.00 9,224.00 and I want to generate all possible sums with a way to id it for output, e.g.: 671.00 + 1,636.00 = 2,307.00 671.00 + 436.00 = 1,107.00 671.00 + 9,224.00 = 9,224.00 671.00 + 1,636.00 + 436.00 = 2,743.00 ... and I would like to do it in Python My current constrains are: a) I'm just learning python now (that's part of the idea) b) I will have to use Python 2.5.2 (no intertools) I think I have found a piece of code that may help: def all_perms(str): if len(str) <=1: yield str else: for perm in all_perms(str[1:]): for i in range(len(perm)+1): #nb str[0:1] works in both string and list contexts yield perm[:i] + str[0:1] + perm[i:] ( from these guys ) But I'm not sure how to use it in my propose. Could someone trow some tips and pieces of code of help? cheers, f.

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  • android thread management onPause

    - by Kwan Cheng
    I have a class that extends the Thread class and has its run method implemented as so. public void run(){ while(!terminate){ if(paused){ Thread.yield(); }else{ accummulator++; } } } This thread is spawned from the onCreate method. When my UI is hidden (when the Home key is pressed) my onPause method will set the paused flag to true and yield the tread. However in the DDMS I still see the uTime of the thread accumulate and its state as "running". So my question is. What is the proper way to stop the thread so that it does not use up CPU time?

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  • Is there a way to make this C# method shorter and more readable with the help of Linq?

    - by Hamish Grubijan
    The following works, but I figured - since it is all based on IEnumerable, Linq can come handy here is well. By the way, is there an equivalent to Directory.GetFiles() which would return an IEnumerable instead of the array? If it exists, then would it make the code run any faster? The last part of the question is inspired by Python language which favors lightweight generators over concrete lists. private IEnumerable<string> getFiles(string strDirectory, bool bCompressedOnly) { foreach (var strFile in Directory.GetFiles(strDirectory)) { // Don't add any existing Zip files since we don't want to delete previously compressed files. if (!bCompressedOnly || Path.GetExtension(strFile).ToLower().Equals(".zip")) { yield return strFile; } } foreach (var strDir in Directory.GetDirectories(strDirectory)) { foreach (var strFile in getFiles(strDir, bCompressedOnly)) { yield return strFile; } } }

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  • How to open a file with chinese name in python.

    - by mahendraliya
    I am trying to open a file in "w" mode with "open()" function in python. The filename is : ?????.jpg. The open function fails with this filename but succeeds with normal files. How can I open a file with names which are not in English in python? My code is as follows: try: filename = urllib.quote(filename.encode('utf-8')) destination = open(filename, 'w') yield("<br>Obtained the file reference") except: yield("<br>Error while opening the file") I always get "Error while opening the file" for non-english filenames. Thanks in advance.

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  • F# working with while loop

    - by mamu
    I have a datareader and i want to return collection of rows from it, after reading books for like a day i am not able to find out best way to do it in f#. I can do it normal C# way in F# but that is not why i am using f# Here is what i am trying to achieve let values = while reader.Read() do yield reader.GetString(0), reader.GetInt64(1) Above is how i am trying to do all values get collected into values, which could be dictinary or tuples or any collection yield can't be used in while loop but that is what i am trying to do What could be the best way to achieve this

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  • Pass off execution to different/specific thread in Java

    - by Mike
    I have about 4 threads. One thread keeps checking some data that the other thread is updating. The others are doing some processing in the background. All have been started at this point. My question is when the checking thread sees that the data has not been updated yet I currently sleep for a little bit but is there any way for me to tell the system to back to executing the thread that does the updating? That or is there any way I can put something like a listener on the data(a String) and once its updated an event will fire that will do what it needs to do? I tried using yield() and it seemed to just keep returning to the thread I called yield() from. Thanks

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  • What will or won't cause a thread to block (a question from a test)

    - by fingerprint211b
    I've had a test, and there was a question I lost some points on, because I wasn't able to answer it : Which of the following is NOT a condition which can cause a thread to block : Calling an objects's wait() method Waiting for an I/O operation Calling sleep() Calling yield() Calling join() As far as I know, all of these are blocking calls : wait() returns when an something calls notify(), blocks until then If the thread is WAITING for an I/O operation then it's obviously blocked sleep(), obviously, blocks until the time runs out, or something wakes up the thread yield() "cancels the rest of the thread's timeslice" (lacking a better term), and returns only when the thread is active again join() blocks until the thread it's waiting for terminates. Am I missing something here?

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  • SQL SERVER – Fix : Error : 3117 : The log or differential backup cannot be restored because no files

    - by pinaldave
    I received the following email from one of my readers. Dear Pinal, I am new to SQL Server and our regular DBA is on vacation. Our production database had some problem and I have just restored full database backup to production server. When I try to apply log back I am getting following error. I am sure, this is valid log backup file. Screenshot is attached. [Few other details regarding server/ip address removed] Msg 3117, Level 16, State 1, Line 1 The log or differential backup cannot be restored because no files are ready to roll forward. Msg 3013, Level 16, State 1, Line 1 RESTORE LOG is terminating abnormally. Screenshot attached. [Removed as it contained live IP address] Please help immediately. Well I have answered this question in my earlier post, 2 years ago, over here SQL SERVER – Fix : Error : Msg 3117, Level 16, State 4 The log or differential backup cannot be restored because no files are ready to rollforward. However, I will try to explain it a little more this time. For SQL Server database to be used it should in online state. There are multiple states of SQL Server Database. ONLINE (Available – online for data) OFFLINE RESTORING RECOVERING RECOVERY PENDING SUSPECT EMERGENCY (Limited Availability) If the database is online, it means it is active and in operational mode. It will not make sense to apply further log from backup if the operations have continued on this database. The common practice during the backup restore process is to specify the keyword RECOVERY when the database is restored. When RECOVERY keyword is specified, the SQL Server brings back the database online and will not accept any further log backups. However, if you want to restore more than one backup files, i.e. after restoring the full back up if you want to apply further differential or log backup you cannot do that when database is online and already active. You need to have your database in the state where it can further accept the backup data and not the online data request. If the SQL Server is online and also accepts database backup file, then there can be data inconsistency. This is the reason that when there are more than one database backup files to be restored, one has to restore the database with NO RECOVERY keyword in the RESTORE operation. I suggest you all to read one more post written by me earlier. In this post, I explained the time line with image and graphic SQL SERVER – Backup Timeline and Understanding of Database Restore Process in Full Recovery Model. Sample Code for reference: RESTORE DATABASE AdventureWorks FROM DISK = 'C:\AdventureWorksFull.bak' WITH NORECOVERY; RESTORE DATABASE AdventureWorks FROM DISK = 'C:\AdventureWorksDiff.bak' WITH RECOVERY; In this post, I am not trying to cover complete backup and recovery. I am just attempting to address one type of error and its resolution. Please test these scenarios on the development server. Playing with live database backup and recovery is always very crucial and needs to be properly planned. Leave a comment here if you need help with this subject. Similar Post: SQL SERVER – Restore Sequence and Understanding NORECOVERY and RECOVERY Note: We will cover Standby Server maintenance and Recovery in another blog post and it is intentionally, not covered this post. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Backup and Restore, SQL Error Messages, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • asynchrony is viral

    - by Daniel Moth
    It is becoming hard to write code today without introducing some form of asynchrony and, if you are using .NET (e.g. for Windows Phone 8 or Windows Store apps), that means sooner or later you have to await something and mark your method as async. My most recent examples included introducing speech recognition in my Translator By Moth phone app where I had to await mySpeechRecognizerUI.RecognizeWithUIAsync() and when moving that code base to a Windows Store project just to show a MessageBox I had to await myMessageDialog.ShowAsync(). Any time you need to invoke an asynchronous method in your code, you have a choice to make: kick off the operation but don’t wait for it to complete (otherwise known as fire-and-forget), synchronously wait for it to complete (which will entail blocking, which can be bad, especially on a UI thread), or asynchronously wait for it to complete before continuing on with the rest of the method’s work. In most cases, you want the latter, and the await keyword makes that trivial to implement.  When you use the magical await keyword in front of an API call, then you typically have to make additional changes to your code: This await usage is within a method of course, and now you have to annotate that method with async. Furthermore, you have to change the return type of the method you just annotated so it returns a Task (if it previously returned void), or Task<myOldReturnType> (if it previously returned myOldReturnType). Note that if it returns void, in some cases you could cheat and stop there. Furthermore, any method that called this method you just annotated with async will now also be invoking an asynchronous operation, so you have to make that change in the body of the caller method to introduce the await keyword before the call to the method. …you guessed it, you now have to change this caller method to be annotated with async and have its return types tweaked... …and it goes on virally… At some point you reach the root of your user code, e.g. a GUI event handler, and whoever calls that void method can already deal with the fact that you marked it as async and the viral introduction of the keywords stops there… This is all wonderful progress and a very powerful mechanism, and I just wish someone had written a refactoring tool to take care of this… anyone? I mentioned earlier that you have a choice when invoking an asynchronous operation. If the first time you encounter this you wish to localize the impact of all these changes and essentially try to turn the asynchronous behavior into synchronous by blocking - don't! For reasons why you don't want to do that, read Toub's excellent blog post (and check out the rest of his blog with gems on async programming starting with the Async FAQ). Just embrace the pattern knowing that when you use one instance of an await, you'll propagate the change all the way to the root user code method, e.g. typically an event handler. Related aside: I just finished re-writing my MessageBox wrapper class for Phone projects, including making it work in Windows Store projects, and it does expect you to use it with an await :-). I'll share that in an upcoming post for those of you that have the same need… Comments about this post by Daniel Moth welcome at the original blog.

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