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  • JSF - Random Number using Beans (JAVA)

    - by Alex Encore Tr
    I am trying to create a jsf application which, upon page refresh increments the hit counter and generates two random numbers. What should be displayed on the window may look something like this: On your On your roll x you have thrown x and x For this program I decided to create two Beans, one to hold the page refresh counter and one to generate a random number. Those look like this for the moment: CounterBean.java package diceroll; public class CounterBean { int count=0; public CounterBean() { } public void setCount(int count) { this.count=count; } public int getCount() { count++; return count; } } RandomNumberBean.java package diceroll; import java.util.Random; public class RandomNumberBean { int rand=0; Random r = new Random(); public RandomNumberBean() { rand = r.nextInt(6); } public void setNextInt(int rand) { this.rand=rand; } public int getNextInt() { return rand; } } I have then created an index.jsp to display the above message. <html> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <f:view> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Roll the Dice</title> </head> <body> <h:form> <p> On your roll # <h:outputText value="#{CounterBean.count} " /> you have thrown <h:outputText value="#{RandomNumberBean.rand}" />and <h:outputText value="#{RandomNumberBean.rand} " /> </p> </h:form> </body> </f:view> </html> However, when I run the application, I get the following message: org.apache.jasper.el.JspPropertyNotFoundException: /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean Caused by: org.apache.jasper.el.JspPropertyNotFoundException - /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean I suppose there's a mistake with my faces-config.xml file, so I will post this here as well, see if somebody can provide some help: faces-config.xml <?xml version="1.0" encoding="UTF-8"?> <faces-config xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd" version="2.0"> <managed-bean> <managed-bean-name>CounterBean</managed-bean-name> <managed-bean-class>diceroll.CounterBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> <managed-bean> <managed-bean-name>RandomNumberBean</managed-bean-name> <managed-bean-class>diceroll.RandomNumberBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> </faces-config>

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  • C# Memoization of functions with arbitrary number of arguments

    - by Lirik
    I'm trying to create a memoization interface for functions with arbitrary number of arguments, but I'm failing miserably. The first thing I tried is to define an interface for a function which gets memoized automatically upon execution: class EMAFunction:IFunction { Dictionary<List<object>, List<object>> map; class EMAComparer : IEqualityComparer<List<object>> { private int _multiplier = 97; public bool Equals(List<object> a, List<object> b) { List<object> aVals = (List<object>)a[0]; int aPeriod = (int)a[1]; List<object> bVals = (List<object>)b[0]; int bPeriod = (int)b[1]; return (aVals.Count == bVals.Count) && (aPeriod == bPeriod); } public int GetHashCode(List<object> obj) { // Don't compute hash code on null object. if (obj == null) { return 0; } // Get length. int length = obj.Count; List<object> vals = (List<object>) obj[0]; int period = (int) obj[1]; return (_multiplier * vals.GetHashCode() * period.GetHashCode()) + length;; } } public EMAFunction() { NumParams = 2; Name = "EMA"; map = new Dictionary<List<object>, List<object>>(new EMAComparer()); } #region IFunction Members public int NumParams { get; set; } public string Name { get; set; } public object Execute(List<object> parameters) { if (parameters.Count != NumParams) throw new ArgumentException("The num params doesn't match!"); if (!map.ContainsKey(parameters)) { //map.Add(parameters, List<double> values = new List<double>(); List<object> asObj = (List<object>)parameters[0]; foreach (object val in asObj) { values.Add((double)val); } int period = (int)parameters[1]; asObj.Clear(); List<double> ema = TechFunctions.ExponentialMovingAverage(values, period); foreach (double val in ema) { asObj.Add(val); } map.Add(parameters, asObj); } return map[parameters]; } public void ClearMap() { map.Clear(); } #endregion } Here are my tests of the function: private void MemoizeTest() { DataSet dataSet = DataLoader.LoadData(DataLoader.DataSource.FROM_WEB, 1024); List<String> labels = dataSet.DataLabels; Stopwatch sw = new Stopwatch(); IFunction emaFunc = new EMAFunction(); List<object> parameters = new List<object>(); int numRuns = 1000; long sumTicks = 0; parameters.Add(dataSet.GetValues("open")); parameters.Add(12); // First call for(int i = 0; i < numRuns; ++i) { emaFunc.ClearMap();// remove any memoization mappings sw.Start(); emaFunc.Execute(parameters); sw.Stop(); sumTicks += sw.ElapsedTicks; } Console.WriteLine("Average ticks not-memoized " + (sumTicks/numRuns)); sumTicks = 0; // Repeat call for (int i = 0; i < numRuns; ++i) { sw.Start(); emaFunc.Execute(parameters); sw.Stop(); sumTicks += sw.ElapsedTicks; } Console.WriteLine("Average ticks memoized " + (sumTicks/numRuns)); } The performance is confusing me... I expected the memoized function to be faster, but it didn't work out that way: Average ticks not-memoized 106,182 Average ticks memoized 198,854 I tried doubling the data instances to 2048, but the results were about the same: Average ticks not-memoized 232,579 Average ticks memoized 446,280 I did notice that it was correctly finding the parameters in the map and it going directly to the map, but the performance was still slow... I'm either open for troubleshooting help with this example, or if you have a better solution to the problem then please let me know what it is.

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  • Regular Expression for CSV with numbers

    - by Bernie Perez
    I'm looking for some regular expression to help parse my CSV file. The file has lines of number,number number,number Comment I want to skip number,number number,number Ex: 319,5446 564425,87 Text to skip 27,765564 I read each line into a string and I wanted to use some regular express to make sure the line matches the pattern of (number,number). If not then don't use the line.

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  • Trying to reduce the speed overhead of an almost-but-not-quite-int number class

    - by Fumiyo Eda
    I have implemented a C++ class which behaves very similarly to the standard int type. The difference is that it has an additional concept of "epsilon" which represents some tiny value that is much less than 1, but greater than 0. One way to think of it is as a very wide fixed point number with 32 MSBs (the integer parts), 32 LSBs (the epsilon parts) and a huge sea of zeros in between. The following class works, but introduces a ~2x speed penalty in the overall program. (The program includes code that has nothing to do with this class, so the actual speed penalty of this class is probably much greater than 2x.) I can't paste the code that is using this class, but I can say the following: +, -, +=, <, > and >= are the only heavily used operators. Use of setEpsilon() and getInt() is extremely rare. * is also rare, and does not even need to consider the epsilon values at all. Here is the class: #include <limits> struct int32Uepsilon { typedef int32Uepsilon Self; int32Uepsilon () { _value = 0; _eps = 0; } int32Uepsilon (const int &i) { _value = i; _eps = 0; } void setEpsilon() { _eps = 1; } Self operator+(const Self &rhs) const { Self result = *this; result._value += rhs._value; result._eps += rhs._eps; return result; } Self operator-(const Self &rhs) const { Self result = *this; result._value -= rhs._value; result._eps -= rhs._eps; return result; } Self operator-( ) const { Self result = *this; result._value = -result._value; result._eps = -result._eps; return result; } Self operator*(const Self &rhs) const { return this->getInt() * rhs.getInt(); } // XXX: discards epsilon bool operator<(const Self &rhs) const { return (_value < rhs._value) || (_value == rhs._value && _eps < rhs._eps); } bool operator>(const Self &rhs) const { return (_value > rhs._value) || (_value == rhs._value && _eps > rhs._eps); } bool operator>=(const Self &rhs) const { return (_value >= rhs._value) || (_value == rhs._value && _eps >= rhs._eps); } Self &operator+=(const Self &rhs) { this->_value += rhs._value; this->_eps += rhs._eps; return *this; } Self &operator-=(const Self &rhs) { this->_value -= rhs._value; this->_eps -= rhs._eps; return *this; } int getInt() const { return(_value); } private: int _value; int _eps; }; namespace std { template<> struct numeric_limits<int32Uepsilon> { static const bool is_signed = true; static int max() { return 2147483647; } } }; The code above works, but it is quite slow. Does anyone have any ideas on how to improve performance? There are a few hints/details I can give that might be helpful: 32 bits are definitely insufficient to hold both _value and _eps. In practice, up to 24 ~ 28 bits of _value are used and up to 20 bits of _eps are used. I could not measure a significant performance difference between using int32_t and int64_t, so memory overhead itself is probably not the problem here. Saturating addition/subtraction on _eps would be cool, but isn't really necessary. Note that the signs of _value and _eps are not necessarily the same! This broke my first attempt at speeding this class up. Inline assembly is no problem, so long as it works with GCC on a Core i7 system running Linux!

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  • Getting can't modify frozen string when using string.insert

    - by Richard
    Hi, This is a quick question. I have the following ruby code, which works fine. def add_zeros number, zeros number = number.to_s zeros_to_add = zeros - number.length zeros_to_add.times do number = "0#{number}" end number end But if I replace number = "0#{number}" With number.insert(0, "0") Then I get TypeError: can't modify frozen string, does anyone know why this is?

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  • Simple prime number program - Weird issue with threads C#

    - by Para
    Hi! This is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace FirePrime { class Program { static bool[] ThreadsFinished; static bool[] nums; static bool AllThreadsFinished() { bool allThreadsFinished = false; foreach (var threadFinished in ThreadsFinished) { allThreadsFinished &= threadFinished; } return allThreadsFinished; } static bool isPrime(int n) { if (n < 2) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } int d = 3; while (d * d <= n) { if (n % d == 0) { return false; } d += 2; } return true; } static void MarkPrimes(int startNumber,int stopNumber,int ThreadNr) { for (int j = startNumber; j < stopNumber; j++) nums[j] = isPrime(j); lock (typeof(Program)) { ThreadsFinished[ThreadNr] = true; } } static void Main(string[] args) { int nrNums = 100; int nrThreads = 10; //var threadStartNums = new List<int>(); ThreadsFinished = new bool[nrThreads]; nums = new bool[nrNums]; //var nums = new List<bool>(); nums[0] = false; nums[1] = false; for(int i=2;i<nrNums;i++) nums[i] = true; int interval = (int)(nrNums / nrThreads); //threadStartNums.Add(2); //int aux = firstStartNum; //int i = 2; //while (aux < interval) //{ // aux = interval*i; // i=i+1; // threadStartNums.Add(aux); //} int startNum = 0; for (int i = 0; i < nrThreads; i++) { var _thread = new System.Threading.Thread(() => MarkPrimes(startNum, Math.Min(startNum + interval, nrNums), i)); startNum = startNum + interval; //set the thread to run in the background _thread.IsBackground = true; //start our thread _thread.Start(); } while (!AllThreadsFinished()) { Thread.Sleep(1); } for (int i = 0; i < nrNums; i++) if(nums[i]) Console.WriteLine(i); } } } This should be a pretty simple program that is supposed to find and output the first nrNums prime numbers using nrThreads threads working in parallel. So, I just split nrNums into nrThreads equal chunks (well, the last one won't be equal; if nrThreads doesn't divide by nrNums, it will also contain the remainder, of course). I start nrThreads threads. They all test each number in their respective chunk and see if it is prime or not; they mark everything out in a bool array that keeps a tab on all the primes. The threads all turn a specific element in another boolean array ThreadsFinished to true when they finish. Now the weird part begins: The threads never all end. If I debug, I find that ThreadNr is not what I assign to it in the loop but another value. I guess this is normal since the threads execute afterwards and the counter (the variable i) is already increased by then but I cannot understand how to make the code be right. Can anyone help? Thank you in advance. P.S.: I know the algorithm is not very efficient; I am aiming at a solution using the sieve of Eratosthenes also with x given threads. But for now I can't even get this one to work and I haven't found any examples of any implementations of that algorithm anywhere in a language that I can understand.

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  • Understanding IIS Bindings

    - by OWScott
    Internet Information Services (IIS) uses 4 decision points for the site bindings.  They are the protocol, port, IP and host header.  This video lesson walks through the bindings and shows how each one is used. This is part 5 of a 52 week series on various topics for the Web Administrator. Other weeks include: Week 1 – Ping and Tracert Week 2 – Understanding DNS zone records Week 3 – Nslookup – the Ultimate DNS Troubleshooting Tool Week 4 – Three Tricks for Capturing Command Line Output Understanding IIS Bindings

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  • What if you could work on anything you wanted?

    - by Nick Harrison
    What if you could work on anything you wanted? Redgate is doing an experiment of sorts this week.  Called Down Tools Week.    The idea is that they stopped working on their regular projects for a week and strike out on something that catches their attention and drives their passion. Evidently in many cases, these projects have turned out to be new features in their existing products that individual were interested in, some were internal iniatives and some where evidently off the wall new ideas.   Today is show and tell where they will share with each other what they have been working on. There may well be some interesting announcements coming out of this.    The prospects are exciting. I understand that Google does something similar allowing their employees a specified amount of time to work on projects of their own choosing.    This has been the breeding ground for some of my favorite services. It is a shame that more companies do not follow such practices.   Now I know that most companies cannot afford to shut down everything for a week and sometimes you can't really explore an interesting idea in 8 hours a week or however much time Google allocates, but still it may be worth while. What would happen if your company gave you as an individual 1 week each quarter to work on a project of your own design and see what happens?   I would be happen if you still had to get approval for before your week long adventure. Personally, I think that this could be a very effective use of training budgets.   Give me a week to research something on my own and you would be amazed at what I can find out.    Maybe this should be the prerequisite before starting a new project.   Stagger the team onboarding but have everyone spend a week long sabbatical studying BizTalk before starting a project that will hinge on BizTalk. The show and tell afterwards is a great way to keep everyone honest or at least reassure management that everyone is honest.    If your goal was to spend a week researching and exploring a new technology and you had to do a show and tell afterwards to show off what you had learned, then everyone can learn a bit of what you just learned.     Sounds like a promising win win for me. Maybe it is a pipe dream, but what if .... What would you work on if given the opportunity to work on anything you wanted?

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  • Sample uniformly at random from an n-dimensional unit simplex.

    - by dreeves
    Sampling uniformly at random from an n-dimensional unit simplex is the fancy way to say that you want n random numbers such that they are all non-negative, they sum to one, and every possible vector of n non-negative numbers that sum to one are equally likely. In the n=2 case you want to sample uniformly from the segment of the line x+y=1 (ie, y=1-x) that is in the positive quadrant. In the n=3 case you're sampling from the triangle-shaped part of the plane x+y+z=1 that is in the positive octant of R3: (Image from http://en.wikipedia.org/wiki/Simplex.) Note that picking n uniform random numbers and then normalizing them so they sum to one does not work. You end up with a bias towards less extreme numbers. Similarly, picking n-1 uniform random numbers and then taking the nth to be one minus the sum of them also introduces bias. Wikipedia gives two algorithms to do this correctly: http://en.wikipedia.org/wiki/Simplex#Random_sampling (Though the second one currently claims to only be correct in practice, not in theory. I'm hoping to clean that up or clarify it when I understand this better. I initially stuck in a "WARNING: such-and-such paper claims the following is wrong" on that Wikipedia page and someone else turned it into the "works only in practice" caveat.) Finally, the question: What do you consider the best implementation of simplex sampling in Mathematica (preferably with empirical confirmation that it's correct)? Related questions http://stackoverflow.com/questions/2171074/generating-a-probability-distribution http://stackoverflow.com/questions/3007975/java-random-percentages

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  • Finding perfect numbers in C# (optimization)

    - by paradox
    I coded up a program in C# to find perfect numbers within a certain range as part of a programming challenge . However, I realized it is very slow when calculating perfect numbers upwards of 10000. Are there any methods of optimization that exist for finding perfect numbers? My code is as follows: using System; using System.Collections.Generic; using System.Linq; namespace ConsoleTest { class Program { public static List<int> FindDivisors(int inputNo) { List<int> Divisors = new List<int>(); for (int i = 1; i<inputNo; i++) { if (inputNo%i==0) Divisors.Add(i); } return Divisors; } public static void Main(string[] args) { const int limit = 100000; List<int> PerfectNumbers = new List<int>(); List<int> Divisors=new List<int>(); for (int i=1; i<limit; i++) { Divisors = FindDivisors(i); if (i==Divisors.Sum()) PerfectNumbers.Add(i); } Console.Write("Output ="); for (int i=0; i<PerfectNumbers.Count; i++) { Console.Write(" {0} ",PerfectNumbers[i]); } Console.Write("\n\n\nPress any key to continue . . . "); Console.ReadKey(true); } } }

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  • Generate random coordinates from area outside of a rectangle?

    - by Rockmaninoff
    Hi all, I'm working on a simple tutorial, and I'd like to randomly generate the positions of the red and green boxes in the accompanying images anywhere inside the dark gray area, but not in the white area. Are there any particularly elegant algorithms to do this? There are some hackish ideas I have that are really simple (continue to generate while the coordinates are not outside the inside rectangle, etc.), but I was wondering if anyone had come up with some neat solutions. Thanks for any help!

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  • Calculation Conundrum - how do I influence another textfield?

    - by LawVS
    Hey! Basically I have a problem in that when certain parameters are used in my calculator app - it makes the result incorrect. The issue is that I have separate text fields for hours and minutes and say for example I have as the start time "13" in one text field and "30" in the other with the finish time "24" and "00" in their respective text fields. The answer should be 10 hours 30 minutes, but the answer I get is 11 hours 30 minutes. The code for this is the following. -(IBAction)done:(id)sender { int result = [finishHours.text intValue] - [startHours.text intValue]; totalHours.text = [NSString stringWithFormat:@"%d", result]; if (result < 0) { totalHours.text = [NSString stringWithFormat:@"%d", result + 24]; } -(IBAction)done2:(id)sender { int result = [startMinutes.text intValue] - [finishMinutes.text intValue]; totalMinutes.text = [NSString stringWithFormat:@"%d", result]; if (result < 0) { totalMinutes.text = [NSString stringWithFormat:@"%d", result + 60]; } } I want to make it so if certain parameters are met, then the totalHours.text is reduced by 1 hour to reflect the total minutes. How would I go about that calculation in code? Thanks!

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  • Generate n-dimensional random numbers in Python

    - by Magsol
    I'm trying to generate random numbers from a gaussian distribution. Python has the very useful random.gauss() method, but this is only a one-dimensional random variable. How could I programmatically generate random numbers from this distribution in n-dimensions? For example, in two dimensions, the return value of this method is essentially distance from the mean, so I would still need (x,y) coordinates to determine an actual data point. I suppose I could generate two more random numbers, but I'm not sure how to set up the constraints. I appreciate any insights. Thanks!

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  • How does this C# asp.net random password code work?

    - by quakkels
    Hello all, I'm new to .NET and C# and I'm trying to figure out how this code works: public static string CreateRandomPassword(int PasswordLength) { String _allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ23456789"; Byte[] randomBytes = new Byte[PasswordLength]; RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); rng.GetBytes(randomBytes); char[] chars = new char[PasswordLength]; int allowedCharCount = _allowedChars.Length; for(int i = 0;i<PasswordLength;i++) { /// /// I don't understand how this line works: /// chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; } return new string(chars); } I think I've got a pretty good handle on most of this. I haven't been able to understand the following line: chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; I understand that the code generates random binary numbers and uses those random numbers in the for loop to select a character from the _allowedChars string. What I don't get is why this code uses the modulous operator (%) to get the _allowedChars index value. Thanks for any help

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  • Why does multiplying a double by -1 not give the negative of the current answer

    - by Ankur
    I am trying to multiply a double value by -1 to get the negative value. It continues to give me a positive value double man = Double.parseDouble(mantissa); double exp; if(sign.equals("plus")){ exp = Double.parseDouble(exponent); } else { exp = Double.parseDouble(exponent); exp = exp*-1; } System.out.println(man+" - "+sign+" - "+exp); The printed result is 13.93 - minus - 2.0 which is correct except that 2.0 should be -2.0

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  • Gamma Distribution in Boost

    - by Kamchatka
    Hello, I'm trying to use the Gamma distribution from boost::math but it looks like it isn't possible to use it with boost::variate_generator. Could someone confirm that? Or is there a way to use it. I discovered that there is a boost::gamma_distribution undocumented that could probably be used too but it only allows to choose the alpha parameter from the distribution and not the beta. Thanks!

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  • regex to format a float in php

    - by Itamar Bar-Lev
    I have a PHP function for formatting a float to a given amount of decimal points that uses number_format(), and then removes the unneeded zeros (and also the '.' if possible): $float = number_format($float, $decimalPlaces, '.', ''); for ($i = 0; $i < $decimalPlaces; $i++) { if (substr($float, strlen($float) - 1, strlen($float)) == '0') { $float = substr($float, 0, strlen($float) - 1); } } if (substr($float, strlen($float) - 1, strlen($float)) == '.') { $float = substr($float, 0, strlen($float) - 1); } Is it possible to do so more effectively with a regular expression?

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  • Filezilla won't connect to my server!

    - by Reece
    Hey guys! I'm awful with computers! I'm trying to use Filezilla to connect to my server. When I do this, this is the message it give me verbatim: Protocol error: Unknown protocol identifier (0x50 0x50 0x48). Most likely connected to the wrong port. Connection to server closed. but it's not the wrong port!... what am I doing wrong?

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  • Best method for converting several sets of numbers with several different ratios

    - by C Patton
    I'm working on an open-source harm reduction application for opioid addicts. One of the features in this application is the conversion (in mg/mcg) between common opioids, so people don't overdose by accident. If you're morally against opioid addiction and wouldn't respond because of your morals, please consider that this application is for HARM REDUCTION.. So people don't end up dead. I have this data.. 3mg morphine IV = 10mcg fentanyl IV 2mg morphine oral = 1mg oxycodone oral 3mg oral morphine = 1mg oxymorphone oral 7.0mg morphine oral = 1mg hydromorphone oral 1mg morphine iv = .10mg oxymorphone iv 1mg morphine oral = 1mg hydrocodone oral 1mg morphine oral = 6.67mg codeine oral 1mg morphine oral = .10mg methadone oral And I have a textbox that is the source dosage in mg (a double) that the user can enter in. Underneath this, I have radio boxes for the source substance (ie: morphine) and the destination substance (ie oxycodone) for conversion.. I've been trying to think of the most efficient way to do this, but nearly every seems sloppy. If I were to do something like public static double MorphinetoOxycodone(string morphineValue) { double morphine = Double.Parse(morphineValue); return (morphine / 2 ); } I would also have to make a function for OxycodonetoMorphine, OxycodonetoCodeine, etc.. and then would end up with dozens functions.. There must be an easier way than this that I'm missing. If you'll notice, all of my conversions use morphine as the base value.. what might be the easiest way to use the morphine value to convert one opioid to another? For example, if 1mg morphine oral is equal to 1mg hydrocodone and 1mg morphine oral is equal to .10mg methadone, wouldn't I just multiply 1*.10 to get the hydrocodone-methadone value? Implementing this idea is what I'm having the most trouble with. Any help would be GREATLY appreciated.. and if you'd like, I would add your name/nickname to the credits in this program. It's possible that many, many people around the world will use this (I'm translating it into several languages as well) and to know that your work could've helped an addict from dying.. I think that's a great thing :) -cory

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  • Negative numbers, arrays javascript!

    - by zizzamia
    I was implementing a routing algorithm in javascript, but when I assign a negative one variable in the array gives me this error: invalid array length. var node = new Array() node[0] = new Array(6,7) node[1] = new Array(5,-4,8) node[2] = new Array(-2) //Here, invalid array length I do not know how to resolve this error.

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  • Ruby on Rails - Currency : commas causing an issue.

    - by easement
    Looking on SO, I see that the preferred way to currency using RoR is using decimal(8,2) and to output them using number_to_currency(); I can get my numbers out of the DB, but I'm having issues on getting them in. Inside my update action I have the following line: if @non_labor_expense.update_attributes(params[:non_labor_expense]) puts YAML::dump(params) The dump of params shows the correct value. xx,yyy.zz , but what gets stored in the DB is only xx.00 What do I need to do in order to take into account that there may be commas and a user may not enter .zz (the cents). Some regex and for comma? how would you handle the decimal if it were .2 versus .20 . There has to be a builtin or at least a better way. My Migration (I don't know if this helps): class ChangeExpenseToDec < ActiveRecord::Migration def self.up change_column :non_labor_expenses, :amount, :decimal, :precision => 8, :scale => 2 end def self.down change_column :non_labor_expenses, :amount, :integer end end

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  • sampling integers uniformly efficiently in python using numpy/scipy

    - by user248237
    I have a problem where depending on the result of a random coin flip, I have to sample a random starting position from a string. If the sampling of this random position is uniform over the string, I thought of two approaches to do it: one using multinomial from numpy.random, the other using the simple randint function of Python standard lib. I tested this as follows: from numpy import * from numpy.random import multinomial from random import randint import time def use_multinomial(length, num_points): probs = ones(length)/float(length) for n in range(num_points): result = multinomial(1, probs) def use_rand(length, num_points): for n in range(num_points): rand(1, length) def main(): length = 1700 num_points = 50000 t1 = time.time() use_multinomial(length, num_points) t2 = time.time() print "Multinomial took: %s seconds" %(t2 - t1) t1 = time.time() use_rand(length, num_points) t2 = time.time() print "Rand took: %s seconds" %(t2 - t1) if __name__ == '__main__': main() The output is: Multinomial took: 6.58072400093 seconds Rand took: 2.35189199448 seconds it seems like randint is faster, but it still seems very slow to me. Is there a vectorized way to get this to be much faster, using numpy or scipy? thanks.

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  • Efficiently generate a 16-character, alphanumeric string

    - by ensnare
    I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table. Would something like this work? def genKey(): hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64") alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash) return alnum_hash[:16] What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances. Or is there a better way to do all this? Thanks.

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