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  • Does anyone have database, programming language/framework suggestions for a GUI point of sale system

    - by Jason Down
    Our company has a point of sale system with many extras, such as ordering and receiving functionality, sales and order history etc. Our main issue is that the system was not designed properly from the ground up, so it takes too long to make fixes and handle requests from our customers. Also, the current technology we are using (Progress database, Progress 4GL for the language) incurs quite a bit of licensing expenses on our customers due to mutli-user license fees for database connections etc. After a lot of discussion it is looking like we will probably start over from scratch (while maintaining the current product at least for the time being). We are looking for a couple of things: Create the system with a nice GUI front end (it is currently CHUI and the application was not built in a way that allows us to redesign the front end... no layering or separation of business logic and gui...shudder). Create the system with the ability to modularize different functionality so the product doesn't have to include all features. This would keep the cost down for our current customers that want basic functionality and a lower price tag. The bells and whistles would be available for those that would want them. Use proper design patterns to make the product easy to add or change any part at any time (i.e. change the database or change the front end without needing to rewrite the application or most of it). This is a problem today because the Progress 4GL code is directly compiled against the database. Small changes in the database requires lots of code recompiling. Our new system will be Linux based, with a possibility of a client application providing functionality from one or more windows boxes. So what I'm looking for is any suggestions on which database and/or framework or programming language(s) someone might recommend for this sort of product. Anyone that has experience in this field might be able to point us in the right direction or even have some ideas of what to avoid. We have considered .NET and SQL Express (we don't need an enterprise level DB), but that would limit us to windows (as far as I know anyway). I have heard of Mono for writing .NET code in a Linux environment, but I don't know much about it yet. We've also considered a Java and MySql based implementation. To summarize we are looking to do the following: Keep licensing costs down on the technology we will use to develop the product (Oracle, yikes! MySQL, nice.) Deliver a solution that is easily maintainable and supportable. A solution that has a component capable of running on "old" hardware through a CHUI front end. (some of our customers have 40+ terminals which would be a ton of cash in order to convert over to a PC). Suggestions would be appreciated. Thanks [UPDATE] I should note that we are currently performing a total cost analysis. This question is intended to give us a couple of "educated" options to look into to include in or analysis. Anyone who could share experiences/suggestions about client/server setups would be appreciated (not just those who have experience with point of sale systems... that would just be a bonus).

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  • Fixed window size app development for Mac OS X

    - by Phil
    I am developing a rather eye-candy application which is to be released on Mac App Store. Due to its graphics intensive use, it would save a great deal of time on UI end if the app could be released with a fixed size main frame-dialog. I did try doing a search regarding App Store policies on the matter but could not find anything. Is the distribution of fixed-size frame [productivity] apps are allowed within the App Store if they conform with other design guidelines?

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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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  • Nicely representing a floating-point number in python

    - by dln385
    I want to represent a floating-point number as a string rounded to some number of significant digits, and never using the exponential format. Essentially, I want to display any floating-point number and make sure it “looks nice”. There are several parts to this problem: I need to be able to specify the number of significant digits. The number of significant digits needs to be variable, which can't be done with with the string formatting operator. I need it to be rounded the way a person would expect, not something like 1.999999999999 I've figured out one way of doing this, though it looks like a work-round and it's not quite perfect. (The maximum precision is 15 significant digits.) >>> def f(number, sigfig): return ("%.15f" % (round(number, int(-1 * floor(log10(number)) + (sigfig - 1))))).rstrip("0").rstrip(".") >>> print f(0.1, 1) 0.1 >>> print f(0.0000000000368568, 2) 0.000000000037 >>> print f(756867, 3) 757000 Is there a better way to do this? Why doesn't Python have a built-in function for this?

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  • Convert pre-IEEE-574 C++ floating-point numbers to/from C#

    - by Richard Kucia
    Before .Net, before math coprocessors, before IEEE-574, Microsoft defined a bit pattern for floating-point numbers. Old versions of the C++ compiler happily used that definition. I am writing a C# app that needs to read/write such floating-point numbers in a file. How can I do the conversions between the 2 bit formats? I need conversion methods in both directions. This app is going to run in a PocketPC/WinCE environment. Changing the structure of the file is out-of-scope for this project. Is there a C++ compiler option that instructs it to use the old FP format? That would be ideal. I could then exchange data between the C# code and C++ code by using a null-terminated text string, and the C++ methods would be simple wrappers around sprintf and atof functions. At the very least, I'm hoping someone can reply with the bit definitions for the old FP format, so I can put together a low-level bit manipulation algorithm if necessary. Thanks.

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  • How to efficiently compare the sign of two floating-point values while handling negative zeros

    - by François Beaune
    Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign. For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) { if (fabs(a) == 0.0f || fabs(b) == 0.0f) return true; return (a >= 0.0f) == (b >= 0.0f); } Assuming the IEEE floating-point model, here's a variant of SameSign that compiles to branchless code (at least with with Visual C++ 2008): bool SameSign(float a, float b) { int ia = binary_cast<int>(a); int ib = binary_cast<int>(b); int az = (ia & 0x7FFFFFFF) == 0; int bz = (ib & 0x7FFFFFFF) == 0; int ab = (ia ^ ib) >= 0; return (az | bz | ab) != 0; } with binary_cast defined as follow: template <typename Target, typename Source> inline Target binary_cast(Source s) { union { Source m_source; Target m_target; } u; u.m_source = s; return u.m_target; } I'm looking for two things: A faster, more efficient implementation of SameSign, using bit tricks, FPU tricks or even SSE intrinsics. An efficient extension of SameSign to three values.

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  • Floating point inaccuracy examples

    - by David Rutten
    How do you explain floating point inaccuracy to fresh programmers and laymen who still think computers are infinitely wise and accurate? Do you have a favourite example or anecdote which seems to get the idea across much better than an precise, but dry, explanation? How is this taught in Computer Science classes?

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  • Why differs floating-point precision in C# when separated by parantheses and when separated by state

    - by Andreas Larsen
    I am aware of how floating point precision works in the regular cases, but I stumbled on an odd situation in my C# code. Why aren't result1 and result2 the exact same floating point value here? const float A; // Arbitrary value const float B; // Arbitrary value float result1 = (A*B)*dt; float result2 = (A*B); result2 *= dt; From this page I figured float arithmetic was left-associative and that this means values are evaluated and calculated in a left-to-right manner. The full source code involves XNA's Quaternions. I don't think it's relevant what my constants are and what the VectorHelper.AddPitchRollYaw() does. The test passes just fine if I calculate the delta pitch/roll/yaw angles in the same manner, but as the code is below it does not pass: X Expected: 0.275153548f But was: 0.275153786f [TestFixture] internal class QuaternionPrecisionTest { [Test] public void Test() { JoystickInput input; input.Pitch = 0.312312432f; input.Roll = 0.512312432f; input.Yaw = 0.912312432f; const float dt = 0.017001f; float pitchRate = input.Pitch * PhysicsConstants.MaxPitchRate; float rollRate = input.Roll * PhysicsConstants.MaxRollRate; float yawRate = input.Yaw * PhysicsConstants.MaxYawRate; Quaternion orient1 = Quaternion.Identity; Quaternion orient2 = Quaternion.Identity; for (int i = 0; i < 10000; i++) { float deltaPitch = (input.Pitch * PhysicsConstants.MaxPitchRate) * dt; float deltaRoll = (input.Roll * PhysicsConstants.MaxRollRate) * dt; float deltaYaw = (input.Yaw * PhysicsConstants.MaxYawRate) * dt; // Add deltas of pitch, roll and yaw to the rotation matrix orient1 = VectorHelper.AddPitchRollYaw( orient1, deltaPitch, deltaRoll, deltaYaw); deltaPitch = pitchRate * dt; deltaRoll = rollRate * dt; deltaYaw = yawRate * dt; orient2 = VectorHelper.AddPitchRollYaw( orient2, deltaPitch, deltaRoll, deltaYaw); } Assert.AreEqual(orient1.X, orient2.X, "X"); Assert.AreEqual(orient1.Y, orient2.Y, "Y"); Assert.AreEqual(orient1.Z, orient2.Z, "Z"); Assert.AreEqual(orient1.W, orient2.W, "W"); } } Granted, the error is small and only presents itself after a large number of iterations, but it has caused me some great headackes.

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  • Floating point mantissa bias

    - by user69514
    Does anybody know how to go out solving this problem? * a = 1.0 × 2^9 * b = -1.0 × 2^9 * c = 1.0 × 2^1 Using the floating-point (the representation uses a 14-bit format, 5 bits for the exponent with a bias of 16, a normalized mantissa of 8 bits, and a single sign bit for the number), perform the following two calculations, paying close attention to the order of operations. * b + (a + c) = ? * (b + a) + c = ?

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  • Point of Sale how to add quantity v2

    - by Jimmy nguyen
    Problem - I have Point of Sale V9 -intuit When ringing up a customer by using a barcode scanner for 1 item and the customer wants multiple of that same item but the receipt shows a long list of that same item. How can I get that program to set it where it would just self update without having to physically touching the keyboard or mouse I would pretty much want it to be user friendly Also if there is a code for this where do I put in the code?

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  • Real life example fo Floating Point error

    - by Rob
    Is there any examples of a company that was burned by floating point data that caused a rounding issue? We're implementing a new system and all the monetary values are stored in floats. I think if i can show actual examples of why this has failed it'll have more weight than the theory of why the values can't be stored properly.

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  • Floating point arithmetics restricted to integers

    - by user396672
    I use doubles for a uniform implementation of some arithmetic calculations. These calculations may be actually applied to integers too, but there are no C++-like templates in Java and I don't want to duplicate the implementation code, so I simply use "double" version for ints. Does JVM spec guarantees the correctness of integer operations such a <=,=, +, -, *, and / (in case of remainder==0) when the operations are emulated as corresponding floating point ops? (Any integer, of course, has reasonable size to be represented in double's mantissa)

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  • Floating point computer - Trouble with getting back correct results

    - by Francisco P.
    Having trouble with a challenge. Let's say I have a theoretical, base 10, floating point calculator with the following characteristics Only 3 digits for mantissa 1 digit for exponent Sign for mantissa and exponent How would this machine compute the following? 300 + \sum_{i=1}^{100} 0.2 The correct result is 320. The machine's result is 300. But why? Can't get where the 20 goes goes missing... Thanks for your time.

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  • Custom Floating Point Representation

    - by Abion47
    I'm trying to write a parser that will read a particular file type, and I need to map the different data types to C# equivalents. Most of them aren't that difficult, but I'm having trouble wrapping my head around what "int16 with a bias of 14" means. I've deduced that it's some kind of floating point type, so my best bet would be to write a converter that would map it to a float, double, or decimal type. I'm not sure where to take it from here, though.

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  • position:fixed on element in ie7/8 and problems with the scrolling of the content inside it

    - by jayarjo
    I got an element fixed in the center of the screen, having specific dimensions (let's say 500x500). The element has content, which is larger then the height of the element and thus causes scroll bar to appear, which is fine. In FF/WebKit everything works nice. However in IE 7/8 ... content of the fixed element doesn't scroll, or scrolls with HUGE delay. If I change position:fixed to position:absolute, it starts to scroll fine, but with position:fixed... it's just a pain!.. Is it some known issue? Anyone heard/encountered something like that? Any ideas how to deal with such?...

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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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  • OOP Design of items in a Point-of-Sale system

    - by Jonas
    I am implementing a Point-of-Sale system. In the system I represent an Item in three places, and I wounder how I should represent them in OOP. First I have the WarehouseItem, that contains price, purchase price, info about the supplier, suppliers price, info about the product and quantity in warehouse. Then I have CartItem, which contains the same fields as WarehouseItem, but adds NrOfItems and Discount. And finally I have ReceiptItem, thats contains an item where I have stripped of info about the supplier, and only contains the price that was payed. Are there any OOP-recommendations, best-practices or design patterns that I could apply for this? I don't really know if CartItem should contain (wrap) an WarehouseItem, or extend it, or if I just should copy the fields that I need. Maybe I should create an Item-class where I keep all common fields, and then extend it to WarehouseItem, CartItem and ReceiptItem. Sometimes I think that it is good to keep the field of the item and just display the information that is needed.

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  • Another floating point question

    - by jeffmax329
    I have read most of the posts on here regarding floating point, and I understand the basic underlying issue that using IEEE 754 (and just by the nature of storing numbers in binary) certain fractions cannot be represented. I am trying to figure out the following: If both Python and JavaScript use the IEEE 754 standard, why is it that executing the following in Python .1 + .1 Results in 0.20000000000000001 (which is to be expected) Where as in Javascript (in at least Chrome and Firefox) the answer is .2 However performing .1 + .2 In both languages results in 0.30000000000000004 In addition, executing var a = 0.3; in JavaScript and printing a results in 0.3 Where as doing a = 0.3 in Python results in 0.29999999999999999 I would like to understand the reason for this difference in behavior. In addition, many of the posts on OS link to a JavaScript port of Java's BigDecimal, but the link is dead. Does anyone have a copy?

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  • Using write to print floating point numbers.

    - by Tom
    Hi, As an exercise to achieve something larger, i'm trying to use write to print a floating point number. I haven't done this in a while. I must be doing something wrong because I cant get it to work. Here is my code #include <unistd.h> int main(){ float f = 4.5; write(1,&f,sizeof float); return 0; } However, when running it im getting ?@ Any thoughts? Thanks in advance.

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  • Floating point innacuracies

    - by Greg
    While writing a function which will perform some operation with each number in a range I ran into some problems with floating point inaccuracies. The problem can be seen in the code below: #include <iostream> using namespace std; int main() { double start = .99999, end = 1.00001, inc = .000001; int steps = (end - start) / inc; for(int i = 0; i <= steps; ++i) { cout << (start + (inc * i)) << endl; } } The problem is that the numbers the above program outputs look like this: 0.99999 0.999991 0.999992 0.999993 0.999994 0.999995 0.999996 0.999997 0.999998 0.999999 1 1 1 1 1 1.00001 1.00001 1.00001 1.00001 1.00001 1.00001 They only appear to be correct up to the first 1. What is the proper way to solve this problem?

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  • Test your internet connection - Emtel Fixed Broadband

    Already at the begin of April, I had a phone conversation with my representative at Emtel Ltd. about some upcoming issues due to the ongoing construction work in my neighbourhood. Unfortunately, they finally raised the house two levels above ours, and of course this has to have a negative impact on the visibility between the WiMAX outdoor unit on the roof and the aimed access point at Medine. So, today I had a technical team here to do a site survey and to come up with potential solutions. Short version: It doesn't look good after all. The site survey Well, the two technicians did their work properly, even re-arranged the antenna to check the connection with another end point down at La Preneuse. But no improvements. Looks like we are out of luck since the construction next door hasn't finished yet and at the moment, it even looks like they are planning to put at least one more level on top. I really wonder about the sanity of the responsible bodies at the local district council. But that's another story. Anyway, the outdoor unit was once again pointed towards Medine and properly fixed with new cable guides (air from the sea and rust...). Both of them did a good job and fine-tuned the reception signal to a mere 3 over 9; compared to the original 7 over 9 I had before the daily terror started. The site survey has been done, and now it's up to Emtel to come up with (better) solutions. Well, I wouldn't mind to have an unlimited, symmetric 3G/UMTS or even LTE connection. Let's see what they can do... Testing the connection There are several online sites available which offer you to check certain aspects of your internet connection. Personally, I'm used to speedtest.net and it works very well. I think it is good and necessary to check your connection from time to time, and only a couple of days ago, I posted the following on Emtel's wall at Facebook (21.05.2013 - 14:06 hrs): Dear Emtel, could you eventually provide an answer on the miserable results of SpeedTest? I chose Rose Hill (Hosted by Emtel Ltd.) as testing endpoint... Sadly, no response to this. Seems that the marketing department is not willing to deal with customers on Facebook. Okay, over at speedtest.net you can use their Flash-based test suite to check your connection to quite a number of servers of different providers world-wide. It's actually very interesting to see the results for different end points and to compare them to each other. The results Following are the results of Rose Hill (hosted by Emtel) and respectively Frankfurt, Germany (hosted by Vodafone DE): Speedtest.net result of 30.05.2013 between Flic en Flac and Rose Hill, Mauritius (Emtel - Fixed Broadband) Speedtest.net result of 30.05.2013 between Flic en Flac and Frankfurt, Germany (Emtel - Fixed Broadband) Luckily, the results are quite similar in terms of connection speed; which is good. I'm currently on a WiMAX tariff called 'Classic Browsing 2', or Fixed Broadband as they call it now, which provides a symmetric line of 768 Kbps (or roughly 0.75 Mbps). In terms of downloads or uploads this means that I would be able to transfer files in either direction with approximately 96 KB/s. Frankly speaking, thanks to compression, my choice of browser and operating system I usually exceed this value and I have download rates up to 120 KB/s - not too bad after all. Only the ping times are a little bit of concern. Due to the difference in distance, or better said based on the number of hubs between the endpoints, they indicate the amount of time that it takes to send a package from your machine to the remote server and get a response back. A lower value is better, and usually the ping is less than 300 ms between Mauritius and Europe. The alternatives in Mauritius Not sure whether I should note this done because for my requirements there are no alternatives to Emtel WiMAX at the moment. It would be great to have your opinion on the situation of internet connectivity in Mauritius. Are there really alternatives? And if so, what are the conditions?

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