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  • K/APL style programming in C++?

    - by anon
    I'm writing code in C++, but I really like K/APL's array-oriented style. Does anyone know of a good set of operator overloading tricks / macros / ... to allow some K/APL -style programming in C++? Thanks!

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  • Enforcing an "end" call whenever there is a corresponding "start" call

    - by Jeff Meatball Yang
    Let's say I want to enforce a rule: Everytime you call "StartJumping()" in your function, you must call "EndJumping()" before you return. When a developer is writing their code, they may simply forget to call EndSomething - so I want to make it easy to remember. I can think of only one way to do this: and it abuses the "using" keyword: class Jumper : IDisposable { public Jumper() { Jumper.StartJumping(); } public void Dispose() { Jumper.EndJumping(); } public static void StartJumping() {...} public static void EndJumping() {...} } public bool SomeFunction() { // do some stuff // start jumping... using(Jumper j = new Jumper()) { // do more stuff // while jumping } // end jumping } Is there a better way to do this?

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  • Good Open Source Code to learn Web Programming

    - by Prabu
    Hi can someone point me to some Good Open Source Code to learn Web Programming (Language doesn't matter). i'm looking for source code of web-applications not frameworks I'm not a beginner, I can code to some extent. I want to know how stuffs are done in real world applications.

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  • Prolog: using the sort/2 predicate

    - by Øyvind Hauge
    So I'm trying to get rid of the wrapper clause by using the sort library predicate directly inside split. What split does is just generating a list of numbers from a list that looks like this: [1:2,3:2,4:6] ---split-- [1,2,3,2,4,6]. But the generated list contains duplicates, and I don't want that, so I'm using the wrapper to combine split and sort, which then generates the desired result: [1,2,3,4,6]. I'd really like to get rid of the wrapper and just use sort within split, however I keep getting "ERROR: sort/2: Arguments are not sufficiently instantiated." Any ideas? Thanks :) split([],[]). split([H1:H2|T],[H1,H2|NT]) :- split(T,NT). wrapper(L,Processed) :- split(L,L2), sort(L2,Processed).

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  • Stepping into Ruby Meta-Programming: Generating proxy methods for multiple internal methods

    - by mstksg
    Hi all; I've multiply heard Ruby touted for its super spectacular meta-programming capabilities, and I was wondering if anyone could help me get started with this problem. I have a class that works as an "archive" of sorts, with internal methods that process and output data based on an input. However, the items in the archive in the class itself are represented and processed with integers, for performance purposes. The actual items outside of the archive are known by their string representation, which is simply number_representation.to_s(36). Because of this, I have hooked up each internal method with a "proxy method" that converts the input into the integer form that the archive recognizes, runs the internal method, and converts the output (either a single other item, or a collection of them) back into strings. The naming convention is this: internal methods are represented by _method_name; their corresponding proxy method is represented by method_name, with no leading underscore. For example: class Archive ## PROXY METHODS ## ## input: string representation of id's ## output: string representation of id's def do_something_with id result = _do_something_with id.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_pair id_1,id_2 result = _do_something_with_pair id_1.to_i(36), id_2.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_these ids result = _do_something_with_these ids.map { |n| n.to_i(36) } return nil if result == nil return result.to_s(36) end def get_many_from id result = _get_many_from id return nil if result == nil # no sparse arrays returned return result.map { |n| n.to_s(36) } end ## INTERNAL METHODS ## ## input: integer representation of id's ## output: integer representation of id's def _do_something_with id # does something with one integer-represented id, # returning an id represented as an integer end def do_something_with_pair id_1,id_2 # does something with two integer-represented id's, # returning an id represented as an integer end def _do_something_with_these ids # does something with multiple integer ids, # returning an id represented as an integer end def _get_many_from id # does something with one integer-represented id, # returns a collection of id's represented as integers end end There are a couple of reasons why I can't just convert them if id.class == String at the beginning of the internal methods: These internal methods are somewhat computationally-intensive recursive functions, and I don't want the overhead of checking multiple times at every step There is no way, without adding an extra parameter, to tell whether or not to re-convert at the end I want to think of this as an exercise in understanding ruby meta-programming Does anyone have any ideas? edit The solution I'd like would preferably be able to take an array of method names @@PROXY_METHODS = [:do_something_with, :do_something_with_pair, :do_something_with_these, :get_many_from] iterate through them, and in each iteration, put out the proxy method. I'm not sure what would be done with the arguments, but is there a way to test for arguments of a method? If not, then simple duck typing/analogous concept would do as well.

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  • MongoMapper: how do I create a model like this

    - by Vladimir R
    Suppose we have two models, Task and User. So a user can have many tasks and tasks should be able to have many users too. But, a task should also have a unique creator who is also a user. Exemple: A task in this context is like this: Task ID, Task Creator, Users who should do the task User_1 creates a task and he is then the creator. User_1 specifies User_2 and User_3 as users who should do the task. So these two last users are not creators of task. How do I create this models so that if I have a task object, I can find it's creator and users who should complete it. And how do I do, if I have a user, to find all tasks he created and all tasks he should complete. Thank you.

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  • Why people do not like OOP? [closed]

    - by Gabriel Šcerbák
    I do not understand why people choose C++ over Smalltalk in past and why Java over Python or Ruby. What is it that ties people so much to the procedural programming and makes it so difficult to go "all the way" to object oriented programming? What makes OOP hard? Should not objects be an abstraction which is easier to grasp for people, i.e. a more natural one than procedures? Is education the problem (because people tend to learn procedural programming before object oriented)?

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  • Experiences with D-programming-language

    - by Dario
    Has someone here ever had experience with the D programming language? It seems to have many nice features but will it ever reach the popularity of those currently widespread languages like C++, Java or C#? So is it worth learning or is it an isolated language with minor prospects.

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  • Which style is preferable when writing this boolean expression?

    - by Jeppe Stig Nielsen
    I know this question is to some degree a matter of taste. I admit this is not something I don't understand, it's just something I want to hear others' opinion about. I need to write a method that takes two arguments, a boolean and a string. The boolean is in a sense (which will be obvious shortly) redundant, but it is part of a specification that the method must take in both arguments, and must raise an exception with a specific message text if the boolean has the "wrong" value. The bool must be true if and only if the string is not null or empty. So here are some different styles to write (hopefully!) the same thing. Which one do you find is the most readable, and compliant with good coding practice? // option A: Use two if, repeat throw statement and duplication of message string public void SomeMethod(bool useName, string name) { if (useName && string.IsNullOrEmpty(name)) throw new SomeException("..."); if (!useName && !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option B: Long expression but using only && and || public void SomeMethod(bool useName, string name) { if (useName && string.IsNullOrEmpty(name) || !useName && !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option C: With == operator between booleans public void SomeMethod(bool useName, string name) { if (useName == string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option D1: With XOR operator public void SomeMethod(bool useName, string name) { if (!(useName ^ string.IsNullOrEmpty(name))) throw new SomeException("..."); // rest of method } // option D2: With XOR operator public void SomeMethod(bool useName, string name) { if (useName ^ !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } Of course you're welcome to suggest other possibilities too. Message text "..." would be something like "If 'useName' is true a name must be given, and if 'useName' is false no name is allowed".

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  • Rails find :conditions

    - by Sam
    I have a Reservation model that I'm searching for with three fields. The container_id must always be self.id but as confirmed and auto_confirmed only one needs to be true. I have the following but it doesn't preform what I need: Reservation.find(:all, :conditions => ['container_id = ? AND confirmed = ? OR auto_confirm = ?', self.id, true, true,]) How should I change this?

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  • Hebbian learning

    - by Bane
    I have asked another question on Hebbian learning before, and I guess I got a good answer which I accepted, but, the problem is that I now realize that I've mistaken about Hebbian learning completely, and that I'm a bit confused. So, could you please explain how it can be useful, and what for? Because the way Wikipedia and some other pages describe it - it doesn't make sense! Why would we want to keep increasing the weight between the input and the output neuron if the fire together? What kind of problems can it be used to solve, because when I simulate it in my head, it certainly can't do the basic AND, OR, and other operations (say you initialize the weights at zero, the output neurons never fire, and the weights are never increased!)

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  • Diminishing programmer wants to get back to programming

    - by Marcus TV
    I last programmed actively in 2002. It is almost 8 years now. I learned C and then moved to Visual Basic for our thesis project in the university. I would like to ask suggestions on what programming language should I learn and put to profitability use in areas such as desktop applications, web development, and database applications.

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  • How do you get the logical xor of two variables in Python?

    - by Zach Hirsch
    How do you get the logical xor of two variables in Python? For example, I have two variables that I expect to be strings. I want to test that only one of them contains a True value (is not None or the empty string): str1 = raw_input("Enter string one:") str2 = raw_input("Enter string two:") if logical_xor(str1, str2): print "ok" else: print "bad" The ^ operator seems to be bitwise, and not defined on all objects: >>> 1 ^ 1 0 >>> 2 ^ 1 3 >>> "abc" ^ "" Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for ^: 'str' and 'str'

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  • zChaff not showing output

    - by pns
    Hello, So I downloaded the latest version of zChaff (2007), and was trying out some very simple SAT problems. But zChaff does not output the solution (variable assignments). A very simple example input: p cnf 2 2 1 2 0 1 -2 0 And what I get: c 2 Clauses are true, Verify Solution successful. Instance Satisfiable 1 -2 Random Seed Used 0 Max Decision Level 1 Num. of Decisions 2 ( Stack + Vsids + Shrinking Decisions ) 0 + 1 + 0 Original Num Variables 2 Original Num Clauses 2 Original Num Literals 4 Added Conflict Clauses 0 Num of Shrinkings 0 Deleted Conflict Clauses 0 Deleted Clauses 0 Added Conflict Literals 0 Deleted (Total) Literals 0 Number of Implication 2 Total Run Time 5.1e-05 RESULT: SAT I can see the 1 -2 on the left of "Random Seed Used", but shouldn't this be outputing the variable assignments as "v ..." ? Thanks

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  • Operations on bytes in C#

    - by Hooch
    Hello. I'm writing application to control LEDS on LPT. I have everything working except this. This is one small function. I have sth like that: I want to build function that will take two argument and return one number: In actual code those binary numers will be in hex. I put them there like that so that it's easier for you to visualize it. Example1: arg1 = 1100 1100 arg2 = 1001 0001 retu = 0100 1100 Example2: arg1 = 1111 1111 arg2 = 0001 0010 retu = 1110 1101 Example3: arg1 = 1111 0000 arg2 = 0010 0010 retu = 1101 0000 I have no idea how this function should look like. I want it to be as fast as possible. I'll call this function 200 times per second.

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  • How much time should it take to find the sum of all prime numbers less than 2 million?

    - by Shahensha
    I was trying to solve this Project Euler Question. I implemented the sieve of euler as a helper class in java. It works pretty well for the small numbers. But when I input 2 million as the limit it doesn't return the answer. I use Netbeans IDE. I waited for a lot many hours once, but it still didn't print the answer. When I stopped running the code, it gave the following result Java Result: 2147483647 BUILD SUCCESSFUL (total time: 2,097 minutes 43 seconds) This answer is incorrect. Even after waiting for so much time, this isn't correct. While the same code returns correct answers for smaller limits. Sieve of euler has a very simple algo given at the botton of this page. My implementation is this: package support; import java.util.ArrayList; import java.util.List; /** * * @author admin */ public class SieveOfEuler { int upperLimit; List<Integer> primeNumbers; public SieveOfEuler(int upperLimit){ this.upperLimit = upperLimit; primeNumbers = new ArrayList<Integer>(); for(int i = 2 ; i <= upperLimit ; i++) primeNumbers.add(i); generatePrimes(); } private void generatePrimes(){ int currentPrimeIndex = 0; int currentPrime = 2; while(currentPrime <= Math.sqrt(upperLimit)){ ArrayList<Integer> toBeRemoved = new ArrayList<Integer>(); for(int i = currentPrimeIndex ; i < primeNumbers.size() ; i++){ int multiplier = primeNumbers.get(i); toBeRemoved.add(currentPrime * multiplier); } for(Integer i : toBeRemoved){ primeNumbers.remove(i); } currentPrimeIndex++; currentPrime = primeNumbers.get(currentPrimeIndex); } } public List getPrimes(){ return primeNumbers; } public void displayPrimes(){ for(double i : primeNumbers) System.out.println(i); } } I am perplexed! My questions is 1) Why is it taking so much time? Is there something wrong in what I am doing? Please suggest ways for improving my coding style, if you find something wrong.

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  • Suggest a good book for Quantitative Methods & R Programming

    - by Rahul
    Hi folks, Please suggest a good book for beginner in Quantitative Methods/Techniques. Adding to this, a good book for beginners in R programming language, used in Quantitative Methods. And I've a few questions about this: ? Should I have to learn the other subjects like Probability, Statics, etc. before learning Quantitative Methods ? Is there any relation between Quantitative Methods & Data Mining

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  • VHDL gate basics

    - by balina
    Hello. I'm learning VHDL and I've come to a halt. I'd like to create a simple gate out of smaller gates (a NAND gate here). Here's the code: library IEEE; use IEEE.STD_LOGIC_1164.all; entity ANDGATE2 is port( x,y : in STD_LOGIC; z : out STD_LOGIC ); end ANDGATE2; architecture ANDGATE2 of ANDGATE2 is begin z <= x AND y; end ANDGATE2; library IEEE; use IEEE.STD_LOGIC_1164.all; entity NOTGATE1 is port( x : in STD_LOGIC; z : out STD_LOGIC ); end NOTGATE1; architecture NOTGATE1 of NOTGATE1 is begin z <= NOT x; end NOTGATE1; library ieee; use ieee.std_logic_1164.all; entity NANDGATE2 is port( x : in STD_LOGIC; y : in STD_LOGIC; z : out STD_LOGIC ); end NANDGATE2; architecture NANDGATE2 of NANDGATE2 is signal c, d: std_logic; component NOTGATE1 port( n_in : in STD_LOGIC; n_out : out STD_LOGIC ); end component; component ANDGATE2 port( a_in1, a_in2 : in STD_LOGIC; a_out : out STD_LOGIC ); end component; begin N0: ANDGATE2 port map(x, y, c); N1: NOTGATE1 port map(c, d); z <= d; end NANDGATE2; Here's the code from some tutorial I've been using as a template; it compiles with no problems. library ieee; use ieee.std_logic_1164.all; -- definition of a full adder entity FULLADDER is port ( a, b, c: in std_logic; sum, carry: out std_logic ); end FULLADDER; architecture fulladder_behav of FULLADDER is begin sum <= (a xor b) xor c ; carry <= (a and b) or (c and (a xor b)); end fulladder_behav; -- 4-bit adder library ieee; use ieee.std_logic_1164.all; entity FOURBITADD is port ( a, b: in std_logic_vector(3 downto 0); Cin : in std_logic; sum: out std_logic_vector (3 downto 0); Cout, V: out std_logic ); end FOURBITADD; architecture fouradder_structure of FOURBITADD is signal c: std_logic_vector (4 downto 0); component FULLADDER port ( a, b, c: in std_logic; sum, carry: out std_logic ); end component; begin FA0: FULLADDER port map (a(0), b(0), Cin, sum(0), c(1)); FA1: FULLADDER port map (a(1), b(1), C(1), sum(1), c(2)); FA2: FULLADDER port map (a(2), b(2), C(2), sum(2), c(3)); FA3: FULLADDER port map (a(3), b(3), C(3), sum(3), c(4)); V <= c(3) xor c(4); Cout <= c(4); end fouradder_structure; My code compiles with no errors, but with two warnings: # Warning: ELAB1_0026: p2.vhd : (85, 0): There is no default binding for component "andgate2".(Port "a_in1" is not on the entity). # Warning: ELAB1_0026: p2.vhd : (87, 0): There is no default binding for component "notgate1".(Port "n_in" is not on the entity). What gives?

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