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• How to have Android Service communicate with Activity

  - by Scott Saunders

  I'm writing my first Android application and trying to get my head around communication between services and activities. I have a Service that will run in the background and do some gps and time based logging. I will have an Activity that will be used to start and stop the Service. So first, I need to be able to figure out if the Service is running when the Activity is started. There are some other questions here about that, so I think I can figure that out (but feel free to offer advice). My real problem: if the Activity is running and the Service is started, I need a way for the Service to send messages to the Activity. Simple Strings and integers at this point - status messages mostly. The messages will not happen regularly, so I don't think polling the service is a good way to go if there is another way. I only want this communication when the Activity has been started by the user - I don't want to start the Activity from the Service. In other words, if you start the Activity and the Service is running, you will see some status messages in the Activity UI when something interesting happens. If you don't start the Activity, you will not see these messages (they're not that interesting). It seems like I should be able to determine if the Service is running, and if so, add the Activity as a listener. Then remove the Activity as a listener when the Activity pauses or stops. Is that actually possible? The only way I can figure out to do it is to have the Activity implement Parcelable and build an AIDL file so I can pass it through the Service's remote interface. That seems like overkill though, and I have no idea how the Activity should implement writeToParcel() / readFromParcel(). Is there an easier or better way? Thanks for any help.

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• Bitwise Interval Arithmetic

  - by KennyTM

  I've recently read an interesting thread on the D newsgroup, which basically asks, Given two signed integers a ∈ [amin, amax], b ∈ [bmin, bmax], what is the tightest interval of a | b? I'm think if interval arithmetics can be applied on general bitwise operators (assuming infinite bits). The bitwise-NOT and shifts are trivial since they just corresponds to -1 − x and 2n x. But bitwise-AND/OR are a lot trickier, due to the mix of bitwise and arithmetic properties. Is there a polynomial-time algorithm to compute the intervals of bitwise-AND/OR? Note: Assume all bitwise operations run in linear time (of number of bits), and test/set a bit is constant time. The brute-force algorithm runs in exponential time. Because ~(a | b) = ~a & ~b and a ^ b = (a | b) & ~(a & b), solving the bitwise-AND and -NOT problem implies bitwise-OR and -XOR are done. Although the content of that thread suggests min{a | b} = max(amin, bmin), it is not the tightest bound. Just consider [2, 3] | [8, 9] = [10, 11].)

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• Excel Regex, or export to Python? ; "Vlookup" in Python?

  - by victorhooi

  heya, We have an Excel file with a worksheet containing people records. 1. Phone Number Sanitation One of the fields is a phone number field, which contains phone numbers in the format e.g.: +XX(Y)ZZZZ-ZZZZ (where X, Y and Z are integers). There are also some records which have less digits, e.g.: +XX(Y)ZZZ-ZZZZ And others with really screwed up formats: +XX(Y)ZZZZ-ZZZZ / ZZZZ or: ZZZZZZZZ We need to sanitise these all into the format: 0YZZZZZZZZ (or OYZZZZZZ with those with less digits). 2. Fill in Supervisor Details Each person also has a supervisor, given as an numeric ID. We need to do a lookup to get the name and email address of that supervisor, and add it to the line. This lookup will be firstly on the same worksheet (i.e. searching itself), and it can then fallback to another workbook with more people. 3. Approach? For the first issue, I was thinking of using regex in Excel/VBA somehow, to do the parsing. My Excel-fu isn't the best, but I suppose I can learn...lol. Any particular points on this one? However, would I be better off exporting the XLS to a CSV (e.g. using xlrd), then using Python to fix up the phone numbers? For the second approach, I was thinking of just using vlookups in Excel, to pull in the data, and somehow, having it fall through, first on searching itself, then on the external workbook, then just putting in error text. Not sure how to do that last part. However, if I do happen to choose to export to CSV and do it in Python, what's an efficient way of doing the vlookup? (Should I convert to a dict, or just iterate? Or is there a better, or more idiomatic way?) Cheers, Victor

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• XML RPC c# Call returns array of strings and int

  - by chillconsulting

  I'm doing an XML RPC call in ASP.net with c# and the call returns an Array called userinfo with strings and integers in it and I can't seem to figure out how to parse the data and put it into string and int objects... The only thing that compiles is if I make it an Object in the struct. The int returns fines and is referenced easily. Any help would be appreciated - this is what I got. public Page_Load(object sender, EventArgs e){ IValidateSSO proxy = XmlRpcProxyGen.Create<IValidateSSO>(); UserInfoSSOValue ret2 = proxy.UserInfoSSO(ssoAuth, ssoValue); int i = ret2.isonid; } public struct UserInfoSSOValue { public Object userinfo; public int isonid; } [XmlRpcUrl("host")] public interface IValidateSSO : IXmlRpcProxy { [XmlRpcMethod("sso.session_userinfo")] UserInfoSSOValue UserInfoSSO(string ssoauth, string sid); } Here is what the xml rpc calls returns (I know it's in php... I'm trying to implement in c#): sso.session_userinfo(string $ssoauth, string $sid) string $ssoauth - authentication string (assigned by ONID support) string $sid - sid to get info on Returns: Array ( [userinfo] => Array ( [lastname] => College [expire_time] => 1118688011 [osuuid] => 12345678901 [sid_length] => 3600 [ip] => 10.0.0.1 [sid] => WiT7ppAEUKS3rJ2lNz3Ue64sGPxnnLL0 [username] => collegej [firstname] => Joe [fullname] => College, Joe Student [email] => [email protected] [create_time] => 1118684410 ) [isonid] => 1 ) array userinfo - array containing basic user information

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• Project Euler Question 14 (Collatz Problem)

  - by paradox

  The following iterative sequence is defined for the set of positive integers: n -n/2 (n is even) n -3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence: 13 40 20 10 5 16 8 4 2 1 It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1. Which starting number, under one million, produces the longest chain? NOTE: Once the chain starts the terms are allowed to go above one million. I tried coding a solution to this in C using the bruteforce method. However, it seems that my program stalls when trying to calculate 113383. Please advise :) #include <stdio.h> #define LIMIT 1000000 int iteration(int value) { if(value%2==0) return (value/2); else return (3*value+1); } int count_iterations(int value) { int count=1; //printf("%d\n", value); while(value!=1) { value=iteration(value); //printf("%d\n", value); count++; } return count; } int main() { int iteration_count=0, max=0; int i,count; for (i=1; i<LIMIT; i++) { printf("Current iteration : %d\n", i); iteration_count=count_iterations(i); if (iteration_count>max) { max=iteration_count; count=i; } } //iteration_count=count_iterations(113383); printf("Count = %d\ni = %d\n",max,count); }

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• An alternative to reading input from Java's System.in

  - by dvanaria

  I’m working on the UVa Online Judge problem set archive as a way to practice Java, and as a way to practice data structures and algorithms in general. They give an example input file to submit to the online judge to use as a starting point (it’s the solution to problem 100). Input from the standard input stream (java.lang.System.in) is required as part of any solution on this site, but I can’t understand the implementation of reading from System.in they give in their example solution. It’s true that the input file could consist of any variation of integers, strings, etc, but every solution program requires reading basic lines of text input from System.in, one line at a time. There has to be a better (simpler and more robust) method of gathering data from the standard input stream in Java than this: public static String readLn(int maxLg) { byte lin[] = new byte[maxLg]; int lg = 0, car = -1; String line = “”; try { while (lg < maxLg) { car = System.in.read(); if ((car < 0) || (car == ‘\n’)) { break; } lin[lg++] += car; } } catch (java.io.IOException e) { return (null); } if ((car < 0) && (lg == 0)) { return (null); // eof } return (new String(lin, 0, lg)); } I’m really surprised by this. It looks like something pulled directly from K&R’s “C Programming Language” (a great book regardless), minus the access level modifer and exception handling, etc. Even though I understand the implementation, it just seems like it was written by a C programmer and bypasses most of Java’s object oriented nature. Isn’t there a better way to do this, using the StringTokenizer class or maybe using the split method of String or the java.util.regex package instead?

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• What is the best way to send structs containing enum values via sockets in C.

  - by Axel

  I've lots of different structs containing enum members that I have to transmit via TCP/IP. While the communication endpoints are on different operating systems (Windows XP and Linux) meaning different compilers (gcc 4.x.x and MSVC 2008) both program parts share the same header files with type declarations. For performance reasons, the structures should be transmitted directly (see code sample below) without expensively serializing or streaming the members inside. So the question is how to ensure that both compilers use the same internal memory representation for the enumeration members (i.e. both use 32-bit unsigned integers). Or if there is a better way to solve this problem... //type and enum declaration typedef enum { A = 1, B = 2, C = 3 } eParameter; typedef enum { READY = 400, RUNNING = 401, BLOCKED = 402 FINISHED = 403 } eState; #pragma pack(push,1) typedef struct { eParameter mParameter; eState mState; int32_t miSomeValue; uint8_t miAnotherValue; ... } tStateMessage; #pragma pack(pop) //... send via socket tStateMessage msg; send(iSocketFD,(void*)(&msg),sizeof(tStateMessage)); //... receive message on the other side tStateMessage msg_received; recv(iSocketFD,(void*)(&msg_received),sizeof(tStateMessage)); Additionally... Since both endpoints are little endian maschines, endianess is not a problem here. And the pack #pragma solves alignment issues satisfactorily. Thx for your answers, Axel

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• slicing a 2d numpy array

  - by MedicalMath

  The following code: import numpy as p myarr=[[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6]] copy=p.array(myarr) p.mean(copy)[:,1] Is generating the following error message: Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> p.mean(copy)[:,1] IndexError: 0-d arrays can only use a single () or a list of newaxes (and a single ...) as an index I looked up the syntax at this link and I seem to be using the correct syntax to slice. However, when I type copy[:,1] into the Python shell, it gives me the following output, which is clearly wrong, and is probably what is throwing the error: array([1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6]) Can anyone show me how to fix my code so that I can extract the second column and then take the mean of the second column as intended in the original code above? EDIT: Thank you for your solutions. However, my posting was an oversimplification of my real problem. I used your solutions in my real code, and got a new error. Here is my real code with one of your solutions that I tried: filteredSignalArray=p.array(filteredSignalArray) logical=p.logical_and(EndTime-10.0<=matchingTimeArray,matchingTimeArray<=EndTime) finalStageTime=matchingTimeArray.compress(logical) finalStageFiltered=filteredSignalArray.compress(logical) for j in range(len(finalStageTime)): if j == 0: outputArray=[[finalStageTime[j],finalStageFiltered[j]]] else: outputArray+=[[finalStageTime[j],finalStageFiltered[j]]] print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() And here is the error message that is now being generated by the new code: File "mypath\myscript.py", line 1545, in WriteToOutput10SecondsBeforeTimeMarker print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() TypeError: list indices must be integers, not tuple Second EDIT: This is solved now that I added: outputArray=p.array(outputArray) above my code. I have been at this too many hours and need to take a break for a while if I am making these kinds of mistakes.

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• 48-bit bitwise operations in Javascript?

  - by randomhelp

  I've been given the task of porting Java's Java.util.Random() to JavaScript, and I've run across a huge performance hit/inaccuracy using bitwise operators in Javascript on sufficiently large numbers. Some cursory research states that "bitwise operators in JavaScript are inherently slow," because internally it appears that JavaScript will cast all of its double values into signed 32-bit integers to do the bitwise operations (see https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Operators/Bitwise_Operators for more on this.) Because of this, I can't do a direct port of the Java random number generator, and I need to get the same numeric results as Java.util.Random(). Writing something like this.next = function(bits) { if (!bits) { bits = 48; } this.seed = (this.seed * 25214903917 + 11) & ((1 << 48) - 1); return this.seed >>> (48 - bits); }; (which is an almost-direct port of the Java.util.Random()) code won't work properly, since Javascript can't do bitwise operations on an integer that size.) I've figured out that I can just make a seedable random number generator in 32-bit space using the Lehmer algorithm, but the trick is that I need to get the same values as I would with Java.util.Random(). What should I do to make a faster, functional port?

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• Clipped UITextField with UITextFieldAlignmentRight

  - by Typeoneerror

  Got a small problem with UITextField. I have a simple UITextField and when I set the textAlignment property to "right", it gets clipped by 1-2 pixels. It looks shite so I'm hoping someone has an idea of how to remedy this. I've tried setting the frame to integers to prevent them from being on .5 pixels. - (UITextField *)textControlForSetting:(NSDictionary *)settings { CGRect frame = CGRectIntegral(CGRectMake(100.0f, 0.0f, 170.0f, 44.0f)); UITextField *textField = [[[UITextField alloc] initWithFrame:frame] autorelease]; NSString *defaultValue = [settings objectForKey:kDefaultValueKey]; NSString *currentValue = [prefs objectForKey:[settings objectForKey:kSettingKey]]; textField.tag = settingsCounter; textField.delegate = self; textField.textAlignment = UITextAlignmentRight; textField.font = [UIFont fontWithName:@"HelveticaNeue" size:14.0f]; textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter; textField.placeholder = (currentValue != nil) ? currentValue : defaultValue; settingsCounter++; return textField; }

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• Python: combining making two scripts into one

  - by Alex

  I have two separately made python scripts one that makes a sine wave sound based off time, and another that produces a sine wave graph that is based off the same time factors. I need help combining them into one running file. Here's the first: from struct import pack from math import sin, pi import time def au_file(name, freq, freq1, dur, vol): fout = open(name, 'wb') # header needs size, encoding=2, sampling_rate=8000, channel=1 fout.write('.snd' + pack('>5L', 24, 8*dur, 2, 8000, 1)) factor = 2 * pi * freq/8000 factor1 = 2 * pi * freq1/8000 # write data for seg in range(8 * dur): # sine wave calculations sin_seg = sin(seg * factor) + sin(seg * factor1) fout.write(pack('b', vol * 64 * sin_seg)) fout.close() t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis * 100 tim = float(ti) tim = tim * 100 if __name__ == '__main__': au_file(name='timeSound.au', freq=tim, freq1=tis, dur=1000, vol=1.0) import os os.startfile('timeSound.au') and the second is this: from Tkinter import * import math import time t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis / 100 tim = float(ti) tim = tim / 100 root = Tk() root.title("This very moment") width = 400 height = 300 center = height//2 x_increment = 1 # width stretch x_factor1 = tis x_factor2 = tim # height stretch y_amplitude = 50 c = Canvas(width=width, height=height, bg='black') c.pack() str1 = "sin(x)=white" c.create_text(10, 20, anchor=SW, text=str1) center_line = c.create_line(0, center, width, center, fill='red') # create the coordinate list for the sin() curve, have to be integers xy1 = [] xy2 = [] for x in range(400): # x coordinates xy1.append(x * x_increment) xy2.append(x * x_increment) # y coordinates xy1.append(int(math.sin(x * x_factor1) * y_amplitude) + center) xy2.append(int(math.sin(x * x_factor2) * y_amplitude) + center) sinS_line = c.create_line(xy1, fill='white') sinM_line = c.create_line(xy2, fill='yellow') root.mainloop()

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• Understanding floating point problems

  - by Maxim Gershkovich

  Could someone here please help me understand how to determine when floating point limitations will cause errors in your calculations. For example the following code. CalculateTotalTax = function (TaxRate, TaxFreePrice) { return ((parseFloat(TaxFreePrice) / 100) * parseFloat(TaxRate)).toFixed(4); }; I have been unable to input any two values that have caused for me an incorrect result for this method. If I remove the toFixed(4) I can infact see where the calculations start to lose accuracy (somewhere around the 6th decimal place). Having said that though, my understanding of floats is that even small numbers can sometimes fail to be represented or have I misunderstood and can 4 decimal places (for example) always be represented accurately. MSDN explains floats as such... This means they cannot hold an exact representation of any quantity that is not a binary fraction (of the form k / (2 ^ n) where k and n are integers) Now I assume this applies to all floats (inlcuding those used in javascript). Fundamentally my question boils down to this. How can one determine if any specific method will be vulnerable to errors in floating point operations, at what precision will those errors materialize and what inputs will be required to produce those errors? Hopefully what I am asking makes sense.

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• Minimal-change algorithm which maximises 'swapping'

  - by Kim Bastin

  This is a question on combinatorics from a non-mathematician, so please try to bear with me! Given an array of n distinct characters, I want to generate subsets of k characters in a minimal-change order, i.e. an order in which generation n+1 contains exactly one character that was not in generation n. That's not too hard in itself. However, I also want to maximise the number of cases in which the character that is swapped out in generation n+1 is the same character that was swapped in in generation n. To illustrate, for n=7, k=3: abc abd abe* abf* abg* afg aeg* adg* acg* acd ace* acf* aef adf* ade bde bdf bef bcf* bce bcd* bcg* bdg beg* bfg* cfg ceg* cdg* cde cdf* cef def deg dfg efg The asterisked strings indicate the case I want to maximise; e.g. the e that is new in generation 3, abe, replaces a d that was new in generation 2, abd. It doesn't seem possible to have this happen in every generation, but I want it to happen as often as possible. Typical array sizes that I use are 20-30 and subset sizes around 5-8. I'm using an odd language, Icon (or actually its derivative Unicon), so I don't expect anyone to post code that I can used directly. But I will be grateful for answers or hints in pseudo-code, and will do my best to translate C etc. Also, I have noticed that problems of this kind are often discussed in terms of arrays of integers, and I can certainly apply solutions posted in such terms to my own problem. Thanks Kim Bastin

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• Array: mathematical sequence

  - by VaioIsBorn

  An array of integers A[i] (i 1) is defined in the following way: an element A[k] ( k 1) is the smallest number greater than A[k-1] such that the sum of its digits is equal to the sum of the digits of the number 4* A[k-1] . You need to write a program that calculates the N th number in this array based on the given first element A[1] . INPUT: In one line of standard input there are two numbers seperated with a single space: A[1] (1 <= A[1] <= 100) and N (1 <= N <= 10000). OUTPUT: The standard output should only contain a single integer A[N] , the Nth number of the defined sequence. Input: 7 4 Output: 79 Explanation: Elements of the array are as follows: 7, 19, 49, 79... and the 4th element is solution. I tried solving this by coding a separate function that for a given number A[k] calculates the sum of it's digits and finds the smallest number greater than A[k-1] as it says in the problem, but with no success. The first testing failed because of a memory limit, the second testing failed because of a time limit, and now i don't have any possible idea how to solve this. One friend suggested recursion, but i don't know how to set that. Anyone who can help me in any way please write, also suggest some ideas about using recursion/DP for solving this problem. Thanks.

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• Sorting ArrayList - IndexOutOfBoundsException -Java

  - by FILIaS

  I'm trying to sort an ArrayList with strings(PlayersNames) and imageIcons(PlayersIcons) based on the values i store in an other arrayList with integers(results). As you can see i get an indexOutOfBoundsException but i cant understand why. Maybe the earling of the morning makes me not to see plain things. ArrayList<String> PlayersNames=new ArrayList<String>; ArrayList<ImageIcon> PlayersIcons=new ArrayList<ImageIcons>; public void sortPlayers(ArrayList<Integer> results){ String tmp; ImageIcon tmp2; for (int i=0; i<PlayersNames.size(); i++) { for (int j=PlayersNames.size(); j>i; j--) { if (results.get(i) < results.get(i+1) ) { //IndexOutOfBoundsException! tmp=PlayersNames.get(i+1); PlayersNames.set(i+1,PlayersNames.get(i)); PlayersNames.set(i,tmp); tmp2=PlayersIcons.get(i+1); PlayersIcons.set(i+1,PlayersIcons.get(i)); PlayersIcons.set(i,tmp2); } } } }

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• Convert 4 bytes to int

  - by Oscar Reyes

  I'm reading a binary file like this: InputStream in = new FileInputStream( file ); byte[] buffer = new byte[1024]; while( ( in.read(buffer ) > -1 ) { int a = // ??? } What I want to do it to read up to 4 bytes and create a int value from those but, I don't know how to do it. I kind of feel like I have to grab 4 bytes at a time, and perform one "byte" operation ( like << & FF and stuff like that ) to create the new int What's the idiom for this? EDIT Ooops this turn out to be a bit more complex ( to explain ) What I'm trying to do is, read a file ( may be ascii, binary, it doesn't matter ) and extract the integers it may have. For instance suppose the binary content ( in base 2 ) : 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010 The integer representation should be 1 , 2 right? :- / 1 for the first 32 bits, and 2 for the remaining 32 bits. 11111111 11111111 11111111 11111111 Would be -1 and 01111111 11111111 11111111 11111111 Would be Integer.MAX_VALUE ( 2147483647 )

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• Read a buffer of unknown size (Console input)

  - by Sanarothe

  Hi. I'm a little behind in my X86 Asm class, and the book is making me want to shoot myself in the face. The examples in the book are insufficient and, honestly, very frustrating because of their massive dependencies upon the author's link library, which I hate. I wanted to learn ASM, not how to call his freaking library, which calls more of his library. Anyway, I'm stuck on a lab that requires console input and output. So far, I've got this for my input: input PROC INVOKE ReadConsole, inputHandle, ADDR buffer, Buf - 2, ADDR bytesRead, 0 mov eax,OFFSET buffer Ret input EndP I need to use the input and output procedures multiple times, so I'm trying to make it abstract. I'm just not sure how to use the data that is set to eax here. My initial idea was to take that string array and manually crawl through it by adding 8 to the offset for each possible digit (Input is integer, and there's a little bit of processing) but this doesn't work out because I don't know how big the input actually is. So, how would you swap the string array into an integer that could be used? Full code: (Haven't done the integer logic or the instruction string output because I'm stuck here.) include c:/irvine/irvine32.inc .data inputHandle HANDLE ? outputHandle HANDLE ? buffer BYTE BufSize DUP(?),0,0 bytesRead DWORD ? str1 BYTE "Enter an integer:",0Dh, 0Ah str2 BYTE "Enter another integer:",0Dh, 0Ah str3 BYTE "The higher of the two integers is: " int1 WORD ? int2 WORD ? int3 WORD ? Buf = 80 .code main PROC call handle push str1 call output call input push str2 call output call input push str3 call output call input main EndP larger PROC Ret larger EndP output PROC INVOKE WriteConsole Ret output EndP handle PROC USES eax INVOKE GetStdHandle, STD_INPUT_HANDLE mov inputHandle,eax INVOKE GetStdHandle, STD_INPUT_HANDLE mov outputHandle,eax Ret handle EndP input PROC INVOKE ReadConsole, inputHandle, ADDR buffer, Buf - 2, ADDR bytesRead, 0 mov eax,OFFSET buffer Ret input EndP END main

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• Banning by IP with php/mysql

  - by incrediman

  I want to be able to ban users by IP. My idea is to keep a list of IP's as rows in an BannedIPs table (the IP column would be an index). To check users' IP's against the table, I will keep a session variable called $_SESSION['IP'] for each session. If on any request, $_SESSION['IP'] doesn't match $_SERVER['REMOTE_ADDR'], I will update $_SESSION['IP'] and check the BannedIPs table to see if the IP is banned. (A flag will also be saved as a session variable specifying whether or not the user is banned) Here are the things I'm wondering: Does that sound like a good strategy with regards to speed and security (would someone be able to get around the IP ban somehow, other than changing IP's)? What's the best way to structure a mysql query that checks to see if a row exists? That is, what's the best way to query the db to see if a row with a certain IP exists (to check if it's banned)? Should I save the IP's as integers or strings? Note that... I estimate there will be between 1,000-10,000 banned IP's stored in the database. $_SERVER['REMOTE_ADDR'] is the IP from which the current request was sent.

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• PHP mysqli Insert not working, but not giving any errors.

  - by asdasdas

  As the title says Im trying to do a simple insert, but nothing actually is inserted into the table. I try to print out errors, but nothing is reported. My users table has many more fields than these 4, but they should all default. $query = 'INSERT INTO users (username, password, level, name) VALUES (?, ?, ?, ?)'; if($stmt = $db -> prepare($query)) { $stmt -> bind_param('ssis', $username, $password, $newlevel, $realname); $stmt -> execute(); $stmt -> close(); echo 'Any Errors: '.$db->error.PHP_EOL; } There are no errors given, but when I go to look at the table in phpmyadmin there is not a new row added. I know for sure that the types are correct (strings and integers). Is there something really wrong here or does it have something to do with the fact that I'm ignoring other columns. I have about 8 columns in the user table.

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• Using LINQ in generic collections

  - by Hugo S Ferreira

  Hi, Please consider the following snippet from an implementation of the Interpreter pattern: public override object Execute(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable<string>; return (list != null) ? list.FirstOrDefault() : null; } What about if I want to use the same function for integers? public override object Execute(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable<string>; if (list != null) return list.FirstOrDefault(); var list = ctx as IEnumerable<int>; return (list != null) ? list.FirstOrDefault() : null; } What I wanted was something like: public override object Execute(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable; return (list != null) ? list.FirstOrDefault() : null; } But Linq doesn't act on IEnumerables. Instead, to get to this solution, I would be forced to write something like: public override object Execute(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable; if (list != null) foreach(var i in list) { yield return i; return; } return null; } Or use a generic method: public override T Execute<T>(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable<T>; return (list != null) ? list.FirstOrDefault() : null; } Which would break the Interpreter pattern (as it was implemented in this system). Covariance would also fail (at least in C#3), though would it work, it would be the exact behavior I wanted: public override object Execute(Interpreter interpreter, object ctx) { var list = ctx as IEnumerable<object>; return (list != null) ? list.FirstOrDefault() : null; } So, my question is: what's the best way to achieve the intended behavior? Thanks :-)

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• Comparing two collections for equality

  - by Crossbrowser

  I would like to compare two collections (in C#), but I'm not sure of the best way to implement this efficiently. I've read the other thread about Enumerable.SequenceEqual, but it's not exactly what I'm looking for. In my case, two collections would be equal if they both contain the same items (no matter the order). Example: collection1 = {1, 2, 3, 4}; collection2 = {2, 4, 1, 3}; collection1 == collection2; // true What I usually do is to loop through each item of one collection and see if it exists in the other collection, then loop through each item of the other collection and see if it exists in the first collection. (I start by comparing the lengths). if (collection1.Count != collection2.Count) return false; // the collections are not equal foreach (Item item in collection1) { if (!collection2.Contains(item)) return false; // the collections are not equal } foreach (Item item in collection2) { if (!collection1.Contains(item)) return false; // the collections are not equal } return true; // the collections are equal However, this is not entirely correct, and it's probably not the most efficient way to do compare two collections for equality. An example I can think of that would be wrong is: collection1 = {1, 2, 3, 3, 4} collection2 = {1, 2, 2, 3, 4} Which would be equal with my implementation. Should I just count the number of times each item is found and make sure the counts are equal in both collections? The examples are in some sort of C# (let's call it pseudo-C#), but give your answer in whatever language you wish, it does not matter. Note: I used integers in the examples for simplicity, but I want to be able to use reference-type objects too (they do not behave correctly as keys because only the reference of the object is compared, not the content).

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• weighted matching algorithm in Perl

  - by srk

  Problem : We have equal number of men and women.each men has a preference score toward each woman. So do the woman for each man. each of the men and women have certain interests. Based on the interest we calculate the preference scores. So initially we have an input in a file having x columns. First column is the person(men/woman) id. id are nothing but 0.. n numbers.(first half are men and next half woman) the remaining x-1 columns will have the interests. these are integers too. now using this n by x-1 matrix... we have come up with a n by n/2 matrix. the new matrix has all men and woman as their rows and scores for opposite sex in columns. We have to sort the scores in descending order, also we need to know the id of person related to the scores after sorting. So here i wanted to use hash table. once we get the scores we need to make up pairs.. for which we need to follow some rules. My trouble is with the second matrix of n by n/2 that needs to give information of which man/woman has how much preference on a woman/man. I need these scores sorted so that i know who is the first preferred woman/man, 2nd preferred and so on for a man/woman. I hope to get good suggestions on the data structures i use.. I prefer php or perl. Thank you in advance

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• Find max integer size that a floating point type can handle without loss of precision

  - by Checkers

  Double has range more than a 64-bit integer, but its precision is less dues to its representation (since double is 64-bit as well, it can't fit more actual values). So, when representing larger integers, you start to lose precision in the integer part. #include <boost/cstdint.hpp> #include <limits> template<typename T, typename TFloat> void maxint_to_double() { T i = std::numeric_limits<T>::max(); TFloat d = i; std::cout << std::fixed << i << std::endl << d << std::endl; } int main() { maxint_to_double<int, double>(); maxint_to_double<boost::intmax_t, double>(); maxint_to_double<int, float>(); return 0; } This prints: 2147483647 2147483647.000000 9223372036854775807 9223372036854775800.000000 2147483647 2147483648.000000 Note how max int can fit into a double without loss of precision and boost::intmax_t (64-bit in this case) cannot. float can't even hold an int. Now, the question: is there a way in C++ to check if the entire range of a given integer type can fit into a loating point type without loss of precision? Preferably, it would be a compile-time check that can be used in a static assertion, and would not involve enumerating the constants the compiler should know or can compute.

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• How can I marshall a vector<int> from a C++ dll to a C# application?

  - by mmr

  I have a C++ function that produces a list of rectangles that are interesting. I want to be able to get that list out of the C++ library and back into the C# application that is calling it. So far, I'm encoding the rectangles like so: struct ImagePatch{ int xmin, xmax, ymin, ymax; } and then encoding some vectors: void MyFunc(..., std::vector<int>& rectanglePoints){ std::vector<ImagePatch> patches; //this is filled with rectangles for(i = 0; i < patches.size(); i++){ rectanglePoints.push_back(patches[i].xmin); rectanglePoints.push_back(patches[i].xmax); rectanglePoints.push_back(patches[i].ymin); rectanglePoints.push_back(patches[i].ymax); } } The header for interacting with C# looks like (and works for a bunch of other functions): extern "C" { __declspec(dllexport) void __cdecl MyFunc(..., std::vector<int>& rectanglePoints); } Are there some keywords or other things I can do to get that set of rectangles out? I found this article for marshalling objects in C#, but it seems way too complicated and way too underexplained. Is a vector of integers the right way to do this, or is there some other trick or approach?

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• Neural Network settings for fast training

  - by danpalmer

  I am creating a tool for predicting the time and cost of software projects based on past data. The tool uses a neural network to do this and so far, the results are promising, but I think I can do a lot more optimisation just by changing the properties of the network. There don't seem to be any rules or even many best-practices when it comes to these settings so if anyone with experience could help me I would greatly appreciate it. The input data is made up of a series of integers that could go up as high as the user wants to go, but most will be under 100,000 I would have thought. Some will be as low as 1. They are details like number of people on a project and the cost of a project, as well as details about database entities and use cases. There are 10 inputs in total and 2 outputs (the time and cost). I am using Resilient Propagation to train the network. Currently it has: 10 input nodes, 1 hidden layer with 5 nodes and 2 output nodes. I am training to get under a 5% error rate. The algorithm must run on a webserver so I have put in a measure to stop training when it looks like it isn't going anywhere. This is set to 10,000 training iterations. Currently, when I try to train it with some data that is a bit varied, but well within the limits of what we expect users to put into it, it takes a long time to train, hitting the 10,000 iteration limit over and over again. This is the first time I have used a neural network and I don't really know what to expect. If you could give me some hints on what sort of settings I should be using for the network and for the iteration limit I would greatly appreciate it. Thank you!

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