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  • Using free function as pseudo-constructors to exploit template parameter deduction

    - by Poita_
    Is it a common pattern/idiom to use free functions as pseudo-constructors to avoid having to explicitly specify template parameters? For example, everyone knows about std::make_pair, which uses its parameters to deduce the pair types: template <class A, class B> std::pair<A, B> make_pair(A a, B b) { return std::pair<A, B>(a, b); } // This allows you to call make_pair(1, 2), // instead of having to type pair<int, int>(1, 2) // as you can't get type deduction from the constructor. I find myself using this quite often, so I was just wondering if many other people use it, and if there is a name for this pattern?

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  • What are events SQL profiler eventclass numbers 65527,65528,65533,65534

    - by simonsabin
    I’ve been trying to use RML to process some files and couldn’t figure out why the numbers where all so much smaller than they should be. I then found a line in the RML output “Found [TRACE_STOP] event indicating the end of the trace files” This causes RML to stop processing further data, oh. In my case I had stopped the trace to add some error events because the client was experiencing errors. How do I get RML to process all the other data I wondered. This lead me to the eventclasses in the trace...(read more)

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  • Multi-lingual error messages and error numbers

    - by Jon Hopkins
    So we're looking at the possibility of porting our software to support multiple languages and one of the areas we're going to have to deal with is error messages and other notifications. These obviously have to be reported to the users in their own language. Our team (largely) only speak English and even if we were all multi-lingual we're looking at selling to a wide range of countries and could never expect to have a reasonable number of people speaking all languages (we're a small company). The obvious way to get round the language issue when errors or other messages we may get asked about which are being reported is error numbers which would be consistent across language. While these are going to exist in the backend (if only as key on the error message), I'd really rather not throw them at users if we don't have to but I don't have any other solution. Anyone have any useful suggestions for alternatives?

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  • Which numeral systems are useful in computer science?

    - by authchir
    I am wondering which numeral system different programmers are using, or would use if their language has support for them. As an example, in C++ we can use: Octal by prefixing with 0 (e.g. 0377) Decimal by default (e.g. 255) Hexadecimal by prefixing with 0x (e.g. 0xff) When working with bitmask, I am using hexadecimal but would sometimes want to be able to express binary numbers directly. I know some programming language support it with 0b syntax (e.g. 0b11111111). Is there any other numeric system useful in some computer science domain (e.g. cryptography, codecs, 3D graphics, etc)?

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  • Numbers on the launcher

    - by pete of ebor
    Using 12.04 LTS - few days ago, I left my machine on while I went out. On my return, the launcher was showing (it is set to be hidden) and there were small numbers 1-9 on the icons and letters s on the bottom-most icon and t on the rubbish bin. System still worked fine, although the launcher remained visible, and would not hide. After about 20 mins work, they suddenly vanished and the launcher hid itself.. is this a normal action ? It hasn't happened since..

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  • How to generate "language-safe" UUIDs?

    - by HappyDeveloper
    I always wanted to use randomly generated strings for my resources' IDs, so I could have shorter URLs like this: /user/4jz0k1 But I never did, because I was worried about the random string generation creating actual words, eg: /user/f*cker. This brings two problems: it might be confusing or even offensive for users, and it could mess with the SEO too. Then I thought all I had to do was to set up a fixed pattern like adding a number every 2 letters. I was very happy with my 'generate_safe_uuid' method, but then I realized it was only better for SEO, and worse for users, because it increased the ratio of actual words being generated, eg: /user/g4yd1ck5 Now I'm thinking I could create a method 'replace_numbers_with_letters', and check that it haven't formed any words against a dictionary or something. Any other ideas? ps. As I write this, I also realized that checking for words in more than one language (eg: english and french, spanish, etc) would be a mess, and I'm starting to love numbers-only IDs again.

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  • Find alternative numbers using IE accelerators and the SayNoTo0870 website

    - by simonsabin
    I’ve been a fan of the the SayNoTo0870 website for ages. I hate it costing me money to phone a company for support of their product. Especially on a mobile phone where 0845 and 0870 numbers are v expensive. So I’ve developed an accelerators for IE one allows you to find an alternative number using the company name and the other by using the original number. You can add the accelerators by going to my downloads page . To use the accelerator just select the company name, right click and navigate to...(read more)

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  • Apache Jmeter + Random Double

    - by Filipe Batista
    Is it possible to generate random double numbers in JMeter? I tried to use the Random in the config element where i have defined the Minimum value: 47.9999 (RND1) Maximum value: 30.9999 (RND2) Then in the selected Prepared Selected Statement i placed this values: Parameter values:${RND1},${RND1},${RND2} Parameter types:DOUBLE,DOUBLE,DOUBLE But it seems not work, because i receive an error: Response message: java.sql.SQLException: Cannot convert class java.lang.String to SQL type requested due to java.lang.NumberFormatException - For input string: "${RND1}"

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  • [PHP] md5(uniqid) makes sense for random unique tokens?

    - by Exception e
    I want to create a token generator that generates tokens that cannot be guessed by the user and that are still unique (to be used for password resets and confirmation codes). I often see this code; does it make sense? md5(uniqid(rand(), true)); According to a comment uniqid($prefix, $moreEntopy = true) yields first 8 hex chars = Unixtime, last 5 hex chars = microseconds. I don't know how the $prefix-parameter is handled.. So if you don't set the $moreEntopy flag to true, it gives a predictable outcome. QUESTION: But if we use uniqid with $moreEntopy, what does hashing it with md5 buy us? Is it better than: md5(mt_rand())

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  • How to get N random string from a {a1|a2|a3} format string?

    - by Pentium10
    Take this string as input: string s="planets {Sun|Mercury|Venus|Earth|Mars|Jupiter|Saturn|Uranus|Neptune}" How would I choose randomly N from the set, then join them with comma. The set is defined between {} and options are separated with | pipe. The order is maintained. Some output could be: string output1="planets Sun, Venus"; string output2="planets Neptune"; string output3="planets Earth, Saturn, Uranus, Neptune"; string output4="planets Uranus, Saturn";// bad example, order is not correct Java 1.5

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  • Pseudo code for instruction description

    - by Claus
    Hi, I am just trying to fiddle around what is the best and shortest way to describe two simple instructions with C-like pseudo code. The extract instruction is defined as follows: extract rd, rs, imm This instruction extracts the appropriate byte from the 32-bit source register rs and right justifies it in the destination register. The byte is specified by imm and thus can take the values 0 (for the least-significant byte) and 3 (for the most-significant byte). rd = 0x0; // zero-extend result, ie to make sure bits 31 to 8 are set to zero in the result rd = (rs && (0xff << imm)) >> imm; // this extracts the approriate byte and stores it in rd The insert instruction can be regarded as the inverse operation and it takes a right justified byte from the source register rs and deposits it in the appropriate byte of the destination register rd; again, this byte is determined by the value of imm tmp = 0x0 XOR (rs << imm)) // shift the byte to the appropriate byte determined by imm rd = (rd && (0x00 << imm)) // set appropriate byte to zero in rd rd = rd XOR tmp // XOR the byte into the destination register This looks all a bit horrible, so I wonder if there is a little bit a more elegant way to describe this bahaviour in C-like style ;) Many thanks, Claus

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  • Pseudo-quicksort time complexity

    - by Ord
    I know that quicksort has O(n log n) average time complexity. A pseudo-quicksort (which is only a quicksort when you look at it from far enough away, with a suitably high level of abstraction) that is often used to demonstrate the conciseness of functional languages is as follows (given in Haskell): quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = quicksort [y | y<-xs, y<p] ++ [p] ++ quicksort [y | y<-xs, y>=p] Okay, so I know this thing has problems. The biggest problem with this is that it does not sort in place, which is normally a big advantage of quicksort. Even if that didn't matter, it would still take longer than a typical quicksort because it has to do two passes of the list when it partitions it, and it does costly append operations to splice it back together afterwards. Further, the choice of the first element as the pivot is not the best choice. But even considering all of that, isn't the average time complexity of this quicksort the same as the standard quicksort? Namely, O(n log n)? Because the appends and the partition still have linear time complexity, even if they are inefficient.

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  • Unobstrusive pseudo-classes and attribute selectors emulation in IE

    - by Álvaro G. Vicario
    I'm trying to emulate some pseudo-classes and attribute selectors in Internet Explorer 6 and 7, such as :focus, :hover or [type=text]. So far, I've managed to add a class name to the affected elements: $("input, textarea, select") .hover(function(){ $(this).addClass("hover"); }, function(){ $(this).removeClass("hover"); }) .focus(function(){ $(this).addClass("focus"); }) .blur(function(){ $(this).removeClass("focus"); }); $("input[type=text]").each(function(){ $(this).addClass("text"); }); However, I'm still forced to duplicate selector in my style sheets: textarea:focus, textarea.focus{ } And, to make things worse, IE6 seems to ignore all the selectors when it finds an attribute: input[type=text], input.text{ /* IE6 ignores this */ } And, of course, IE6 ignores selectors with multiple classes: input.text.focus{ /* IE6 ignores this */ } So I'm likely to end up with this mess: input[type=text]{ /* Rules here */ } input.text{ /* Same rules again */ } input[type=text]:focus{ } input.text_and_focus{ } input.text_and_hover{ } input.text_and_focus_and_hover{ } My question: is there any way to read the rules or computed style defined for a CSS selector and apply it to certain elements, so I only need to maintain one set of standard CSS?

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  • "pseudo-atomic" operations in C++

    - by dan
    So I'm aware that nothing is atomic in C++. But I'm trying to figure out if there are any "pseudo-atomic" assumptions I can make. The reason is that I want to avoid using mutexes in some simple situations where I only need very weak guarantees. 1) Suppose I have globally defined volatile bool b, which initially I set true. Then I launch a thread which executes a loop while(b) doSomething(); Meanwhile, in another thread, I execute b=true. Can I assume that the first thread will continue to execute? In other words, if b starts out as true, and the first thread checks the value of b at the same time as the second thread assigns b=true, can I assume that the first thread will read the value of b as true? Or is it possible that at some intermediate point of the assignment b=true, the value of b might be read as false? 2) Now suppose that b is initially false. Then the first thread executes bool b1=b; bool b2=b; if(b1 && !b2) bad(); while the second thread executes b=true. Can I assume that bad() never gets called? 3) What about an int or other builtin types: suppose I have volatile int i, which is initially (say) 7, and then I assign i=7. Can I assume that, at any time during this operation, from any thread, the value of i will be equal to 7? 4) I have volatile int i=7, and then I execute i++ from some thread, and all other threads only read the value of i. Can I assume that i never has any value, in any thread, except for either 7 or 8? 5) I have volatile int i, from one thread I execute i=7, and from another I execute i=8. Afterwards, is i guaranteed to be either 7 or 8 (or whatever two values I have chosen to assign)?

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  • Formatting Dates, Times and Numbers in ASP.NET

    Formatting is the process of converting a variable from its native type into a string representation. Anytime you display a DateTime or numeric variables in an ASP.NET page, you are formatting that variable from its native type into some sort of string representation. How a DateTime or numeric variable is formatted depends on the culture settings and the format string. Because dates and numeric values are formatted differently across cultures, the .NET Framework bases its formatting on the specified culture settings. By default, the formatting routines use the culture settings defined on the web server, but you can indicate that a particular culture be used anytime you format. In addition to the culture settings, formatting is also affected by a format string, which spells out the formatting details to apply. The .NET Framework contains a bounty of format strings. There are standard format strings, which are typically a single letter that applies detailed formatting logic. For example, the "C" format specifier will format a numeric type as a currency value; the "Y" format specifier displays the month name and four-digit year of the specified DateTime value. There are also custom format strings, which display a apply a very specific formatting rule. These custom format strings can be put together to build more intricate formats. For instance, the format string "dddd, MMMM d" displays the full day of the week name followed by a comma followed by the full name of the month followed by the day of the month. For more involved formatting scenarios, where neither the standard or custom format strings cut the mustard, you can always create your own formatting extension methods. This article explores the standard format strings for dates, times and numbers and includes a number of custom formatting methods I've created and use in my own projects. There's also a demo application you can download that lets you specify a culture and then shows you the output for the standard format strings for the selected culture. Read on to learn more! Read More >

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  • SQL SERVER – Solution – Generating Zero Without using Any Numbers in T-SQL

    - by pinaldave
    SQL Server MVP and my friend My friend Madhivanan has asked very interesting question on his blog regarding How to Generate Zero without using Any Numbers in T-SQL. He has demonstrated various methods how one can generate Zero. When I posted note regarding how one he has generated Zero without using number in my blog post for Free Online Training, blog readers have come up with few very interesting answers. I really found them very interesting and here I am listing them with due credit. Special mention to Andery.ca as the answer Andery provided is the one, I myself come up with after very first look and that is why I had left the same as hint in the original article. anil try this select count(cast(null as int)) or any false condition select count(*) where ‘a’=’b’ Varinder Sandhu It seems every currency symbol that SQL Server supports. Return the same value as zero i tried some as select € select ¥ select £ Andrey.ca select count(*)-count(*) Vinay Kumar Another way for generate zero. select Ascii(‘Y’)-Ascii(‘Y’) OR select LEN(”) I like Madhivanan’s answer. and it was awesome. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Contribution, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Fibonacci numbers in F#

    - by BobPalmer
    As you may have gathered from some of my previous posts, I've been spending some quality time at Project Euler.  Normally I do my solutions in C#, but since I have also started learning F#, it only made sense to switch over to F# to get my math coding fix. This week's post is just a small snippet - spefically, a simple function to return a fibonacci number given it's place in the sequence.  One popular example uses recursion: let rec fib n = if n < 2 then 1 else fib (n-2) + fib(n-1) While this is certainly elegant, the recursion is absolutely brutal on performance.  So I decided to spend a little time, and find an option that achieved the same functionality, but used a recursive function.  And since this is F#, I wanted to make sure I did it without the use of any mutable variables. Here's the solution I came up with: let rec fib n1 n2 c =    if c = 1 then        n2    else        fib n2 (n1+n2) (c-1);;let GetFib num =    (fib 1 1 num);;printfn "%A" (GetFib 1000);; Essentially, this function works through the sequence moving forward, passing the two most recent numbers and a counter to the recursive calls until it has achieved the desired number of iterations.  At that point, it returns the latest fibonacci number. Enjoy!

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  • Creating a newspaper that effects the game's economy?

    - by zardon
    I am writing a game in Objective C/cocos2d where a newspaper is a central part of what controls or rather effects the game's world economy as well as what a city might do (such as increase X, reduce Y) The newspaper is a bit like a "Chance card" in Monopoly, it has an effect on something. My question is, what is the best way to do write a newspaper that has both a random and specific effect within the game. Would the best strategy be to write out all the things a newspaper can affect, a PLIST of headlines (with placeholders). I think Tiny Tower uses a PLIST of events and it randomly picks an event, but I'm not sure how it actually parses it because certain events do different things. But then how do I parse all the scenarios that a newspaper can deliver? A big switch statement seems very long and complicated to do. I am wondering if there is a simpler way to handle this kind of thing. Related to this is that there might be no news that day and I'm not sure what the newspaper should display, should it just display the last headline? So, in summary. 1) A newspaper generates a headline, it affects different things, such as the world economy, prices, how city reacts 2) I need the newspaper to generate headlines (although there may be days when there are no headlines at all), but I am not sure how to parse it without using a big-ass switch statement. Thanks in advance.

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  • Randomly and uniquely iterating over a range

    - by Synetech
    Say you have a range of values (or anything else) and you want to iterate over the range and stop at some indeterminate point. Because the stopping value could be anywhere in the range, iterating sequentially is no good because it causes the early values to be accessed more often than later values (which is bad for things that wear out), and also because it reduces performance since it must traverse extra values. Randomly iterating is better because it will (on average) increase the hit-rate so that fewer values have to be accessed before finding the right one, and also distribute the accesses more evenly (again, on average). The problem is that the standard method of randomly jumping around will result in values being accessed multiple times, and has no automatic way of determining when each value has been checked and thus the whole range has been exhausted. One simplified and contrived solution could be to make a list of each value, pick one at random, then remove it. Each time through the loop, you pick one fromt he set of remaining items. Unfortunately this only works for small lists. As a (forced) example, say you are creating a game where the program tries to guess what number you picked and shows how many guess it took. The range is between 0-255 and instead of asking Is it 0? Is it 1? Is it 2?…, you have it guess randomly. You could create a list of 255 numbers, pick randomly and remove it. But what if the range was between 0-232? You can’t really create a 4-billion item list. I’ve seen a couple of implementations RNGs that are supposed to provide a uniform distribution, but none that area also supposed to be unique, i.e., no repeated values. So is there a practical way to randomly, and uniquely iterate over a range?

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  • Finding maximum number of congruent numbers

    - by Stefan Czarnecki
    Let's say we have a multiset (set with possible duplicates) of integers. We would like to find the size of the largest subset of the multiset such that all numbers in the subset are congruent to each other modulo some m 1. For example: 1 4 7 7 8 10 for m = 2 the subsets are: (1, 7, 7) and (4, 8, 10), both having size 3. for m = 3 the subsets are: (1, 4, 7, 7, 10) and (8), the larger set of size 5. for m = 4 the subsets are: (1), (4, 8), (7, 7), (10), the largest set of size 2. At this moment it is evident that the best answer is 5 for m = 3. Given m we can find the size of the largest subset in linear time. Because the answer is always equal or larger than half of the size of the set, it is enough to check for values of m upto median of the set. Also I noticed it is necessary to check for only prime values of m. However if values in the set are large the algorithm is still rather slow. Does anyone have any ideas how to improve it?

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