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  • C++ performance, for versus while

    - by aaa
    hello. In general (or from your experience), is there difference in performance between for and while loops? What if they are doubly/triply nested? Is vectorization (SSE) affected by loop variant in g++ or Intel compilers? Thank you

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  • How to improve efficiency in loops?

    - by Jacob Worldly
    I have the following code, which translates the input string into morse code. My code runs through every letter in the string and then through every character in the alphabet. This is very inefficient, because what if I was reading from a very large file, instead of a small alphabet string. Is there any way that I could improve my code, Maybe using the module re, to match my string with the morse code characters? morse_alphabet = ".- -... -.-. -.. . ..-. --. .... .. .--- -.- .-.. -- -. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --.." ALPHABET = "abcdefghijklmnopqrstuvwxyz" morse_letters = morse_alphabet.split(" ") result = [] count_character = 0 def t(code): for character in code: count_letter = 0 for letter in ALPHABET: lower_character = code[count_character].lower() lower_letter = letter.lower() if lower_character == lower_letter: result.append(morse_letters[count_letter]) count_letter += 1 count_character += 1 return result

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  • Dealing with infinite loops when constructing states for LR(1) parsing

    - by Bruce
    I'm currently constructing LR(1) states from the following grammar. S->AS S->c A->aA A->b where A,S are nonterminals and a,b,c are terminals. This is the construction of I0 I0: S' -> .S, epsilon --------------- S -> .AS, epsilon S -> .c, epsilon --------------- S -> .AS, a S -> .c, c A -> .aA, a A -> .b, b And I1. From S, I1: S' -> S., epsilon //DONE And so on. But when I get to constructing I4... From a, I4: A -> a.A, a ----------- A -> .aA, a A -> .b, b The problem is A - .aA When I attempt to construct the next state from a, I'm going to once again get the exact same content of I4, and this continues infinitely. A similar loop occurs with S -> .AS So, what am I doing wrong? There has to be some detail that I'm missing, but I've browsed my notes and my book and either can't find or just don't understand what's wrong here. Any help?

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  • Faster quadrature decoder loops with Python code

    - by Kelei
    I'm working with a BeagleBone Black and using Adafruit's IO Python library. Wrote a simple quadrature decoding function and it works perfectly fine when the motor runs at about 1800 RPM. But when the motor runs at higher speeds, the code starts missing some of the interrupts and the encoder counts start to accumulate errors. Do you guys have any suggestions as to how I can make the code more efficient or if there are functions which can cycle the interrupts at a higher frequency. Thanks, Kel Here's the code: # Define encoder count function def encodercount(term): global counts global Encoder_A global Encoder_A_old global Encoder_B global Encoder_B_old global error Encoder_A = GPIO.input('P8_7') # stores the value of the encoders at time of interrupt Encoder_B = GPIO.input('P8_8') if Encoder_A == Encoder_A_old and Encoder_B == Encoder_B_old: # this will be an error error += 1 print 'Error count is %s' %error elif (Encoder_A == 1 and Encoder_B_old == 0) or (Encoder_A == 0 and Encoder_B_old == 1): # this will be clockwise rotation counts += 1 print 'Encoder count is %s' %counts print 'AB is %s %s' % (Encoder_A, Encoder_B) elif (Encoder_A == 1 and Encoder_B_old == 1) or (Encoder_A == 0 and Encoder_B_old == 0): # this will be counter-clockwise rotation counts -= 1 print 'Encoder count is %s' %counts print 'AB is %s %s' % (Encoder_A, Encoder_B) else: #this will be an error as well error += 1 print 'Error count is %s' %error Encoder_A_old = Encoder_A # store the current encoder values as old values to be used as comparison in the next loop Encoder_B_old = Encoder_B # Initialize the interrupts - these trigger on the both the rising and falling GPIO.add_event_detect('P8_7', GPIO.BOTH, callback = encodercount) # Encoder A GPIO.add_event_detect('P8_8', GPIO.BOTH, callback = encodercount) # Encoder B # This is the part of the code which runs normally in the background while True: time.sleep(1)

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  • Vector iterators in for loops, return statements, warning, c++

    - by Crystal
    Had 3 questions regarding a hw assignment for C++. The goal was to create a simple palindrome method. Here is my template for that: #ifndef PALINDROME_H #define PALINDROME_H #include <vector> #include <iostream> #include <cmath> template <class T> static bool palindrome(const std::vector<T> &input) { std::vector<T>::const_iterator it = input.begin(); std::vector<T>::const_reverse_iterator rit = input.rbegin(); for (int i = 0; i < input.size()/2; i++, it++, rit++) { if (!(*it == *rit)) { return false; } } return true; } template <class T> static void showVector(const std::vector<T> &input) { for (std::vector<T>::const_iterator it = input.begin(); it != input.end(); it++) { std::cout << *it << " "; } } #endif Regarding the above code, can you have more than one iterator declared in the first part of the for loop? I tried defining both the "it" and "rit" in the palindrome() method, and I kept on getting an error about needing a "," before rit. But when I cut and paste outside the for loop, no errors from the compiler. (I'm using VS 2008). Second question, I pretty much just brain farted on this one. But is the way I have my return statements in the palindrome() method ok? In my head, I think it works like, once the *it and *rit do not equal each other, then the function returns false, and the method exits at this point. Otherwise if it goes all the way through the for loop, then it returns true at the end. I totally brain farted on how return statements work in if blocks and I tried looking up a good example in my book and I couldn't find one. Finally, I get this warnings: \palindrome.h(14) : warning C4018: '<' : signed/unsigned mismatch Now is that because I run my for loop until (i < input.size()/2) and the compiler is telling me that input can be negative? Thanks!

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  • Elegant Method of Inserting Code Between Loops

    - by DeathMagus
    In web development, I often find I need to format and print various arrays of data, and separate these blocks of data in some manner. In other words, I need to be able to insert code between each loop, without said code being inserted before the first entry or after the last one. The most elegant way I've found to accomplish this is as follows: function echoWithBreaks($array){ for($i=0; $i<count($array); $i++){ //Echo an item if($i<count($array)-1){ //Echo "between code" } } } Unfortunately, there's no way that I can see to implement this solution with foreach instead of for. Does anyone know of a more elegant solution that will work with foreach?

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  • Getting caught in loops - R

    - by user334898
    I am looking at whether or not certain 'systems' for betting really do work as claimed, namely, that they have a positive expectation. One such system is based on the rebate on loss. You basically have a large master pot, say $1 million. Your bankroll for each game is $50k. The way it works, is as follows: 1) Start with $50k, always bet on banker 2) If you win, add the money to the master pot. Then play again with $50k. 3) If you lose(now you're at $30k) play till you either: (a) hit 0, you get a rebate of 10%. Begin playing again with $50k+5k=$55k. (b) If you win more than the initial bankroll, add the money to the master pot. Then play again with $50k. 4) Continue until you double the master pot. I just cant find an easy way of programming out the possible cases in R, since you can eventually go down an improbable path. For example, you start at 50k, lose 20, win 19, now you're at 49, now you lose 20, lose 20, now youre at 9, you either lose 9 and get back 5k or you win and this cycle continues until you either end up with more than 50k or hit 0 and get the rebate on the 50k and start again with $50k +5k. Here's some code i started, but i havent figured out a good way of handling the cases where you get stuck and keeping track of the number of games played. Thanks again for your help. Obviously, I understand you may be busy and not have time. p.loss <- .4462466 p.win <- .4585974 p.tie <- 1 - (p.win+p.loss) prob <- c(p.win,p.tie,p.loss) bet<-20 x <- c(19,0,-20) r <- 10 # rebate = 20% br.i <- 50 br<-200 #for(i in 1:100){ # cbr.i<-0 y <- sample(x,1,replace=T,prob) cbr.i<-y+br.i if(cbr.i > br.i){ br<-br+(cbr.i-br.i); cbr.i<-br.i; }else{ y <- sample(x,2,replace=T,prob); if( sum(y)< cbr.i ){ cbr.i<-br.i+(1/r)*br.i; br<-br-br.i} cbr.i<-y+ }else{ cbr.i<- sum(y) + cbr.i; }if(cbr.i <= bet){ y <- sample(x,1,replace=T,prob) if(abs(y)>cbr.i){ cbr.i<-br.i+(1/r)*br.i } }

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  • Pointers in For loops

    - by Bobby
    Quick question: I am a C# guy debugging a C++ app so I am not used to memory management. In the following code: for(int i = 0; i < TlmMsgDB.CMTGetTelemMsgDBCount(); i++) { CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i); CMT_SINT32_Tdef id = telm->CMTGetPackingMapID(); ManualScheduleTables.SetManualMsg(i,id); ManualScheduleTables.SetManExec(i,false); } Am I leaking memory every iteration b/c of CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i);? The "CMTGetTelemetryMsg(int)" method returns a pointer. Do I have to "delete telm;" at the end of each iteration?

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  • System loops using non-integers?

    - by mary
    I wrote a .sh file to compile and run a few programs for a homework assignment. I have a "for" loop in the script, but it won't work unless I use only integers: #!/bin/bash for (( i=10; i<=100000; i+=100)) do ./hw3_2_2 $i done The variable $i is an input for the program hw3_2_2, and I have non-integer values I'd like to use. How could I loop through running the code with a list of decimal numbers?

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  • Attempt to create nested for loops generating missing arguments error

    - by JerryK
    Am attempting to teach myself to program using Tcl. (I want to become more familiar with the language to understand someone else's code - SCID chess) The task i've set myself to motivate my learing of Tcl is to solve the 8 queens problem. My approach to creating a program is to sucessively 'prototype' a solution. So. I'm up to nesting a for loop holding the q pos on row 2 inside the for loop holding the q pos on row 1 Here is my code set allowd 1 set notallowd 0 for {set r1p 1} {$r1p <= 8} {incr r1p } { puts "1st row q placed at $r1p" ;# re-initialize r2 'free for q placemnt' array after every change of r1 q pos: for {set i 1 } {$i <= 8} {incr i} { set r2($i) $allowd } for { set r2($r1p) $notallowd ; set r2([eval $r1p-1]) $notallowd ; set r2([eval $r1p+1]) $notallowd ; set r2p 1} {$r2p <= 8} { incr r2p ;# end of 'next' arg of r2 forloop } ;# commnd arg of r2 forloop placed below: {puts "2nd row q placed at $r2p" } } My problem is that when i run the code the interpreter is aborting with the fatal error: "wrong #args should be for start test next command. I've gone over my code a few times and can't see that i've missed any of the for loop arguments.

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  • linked list sort function only loops once

    - by Tristan Pearce
    i have a singly linked list that i am trying to sort from least to greatest by price. here is what i have so far struct part { char* name; float price; int quantity; struct part *next; }; typedef struct part partType; partType *sort_price(partType **item) { partType *temp1 = *item; partType *temp2 = (*item)->next; if ( *item == NULL || (*item)->next == NULL ) return *item; else { while ( temp2 != NULL && temp2->next != NULL ){ if (temp2->price > temp2->next->price){ temp1->next = temp2->next; temp2->next = temp2->next->next; temp1->next->next = temp2; } temp1 = temp2; temp2 = temp2->next; } } return *item; } the list is already populated but when i call the sort function it only swaps the first two nodes that satisfy the condition in the if statement. I dont understand why it doesnt do the check again after the two temp pointers are incremented.

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  • Php pi help... (Loops)

    - by James Rattray
    Is this iteration the best? (Pi^2)/12 = 1 - 1/4 + 1/9 - 1/16 + 1/25 etc. -For converging faster? If not please answer with the iteration -preferably in the form above (an example) -not a splat of algebra ... I'm doing this to find Pi to 1,000,000,000 places online.

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  • Php pi help... (Loops)

    - by James Rattray
    Is this iteration the best? (Pi^2)/12 = 1 - 1/4 + 1/9 - 1/16 + 1/25 etc. -For converging faster? If not please answer with the iteration -preferably in the form above (an example) -not a splat of algebra ... I'm doing this to find Pi to 1,000,000,000 places online. http://www.zombiewrath.com/superpi.php or my 10,000 one: http://www.zombiewrath.com/pi.php

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  • Java Applet : Nested Loops color change

    - by Bader
    Hello I have like a table to make a nested loop in Java applet , during this loop i should change the colors like the picture said. now i successed to make the table but i cannot change the colors because every time i try a forumla , it doesn't work. Here is my code int x = 63; for (int r=1; r<=10;r++) { Color C = new Color(0,10 +(x * 2),0); for (int c=0; c<=4; c++) { Color C2 = new Color(10 + (x * 2) ,0,0); g.setColor(C2); Font F = new Font("Arial",Font.BOLD, 24); g.setFont(F); g.drawString("Hello",10 + ( c * 60), r * 25 ); } } what should i do to make it work ?

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  • String loops in Python

    - by Steve Hunter
    I have two pools of strings and I would like to do a loop over both. For example, if I want to put two labeled apples in one plate I'll write: basket1 = ['apple#1', 'apple#2', 'apple#3', 'apple#4'] for fruit1 in basket1: basket2 = ['apple#1', 'apple#2', 'apple#3', 'apple#4'] for fruit2 in basket2: if fruit1 == fruit2: print 'Oops!' else: print "New Plate = %s and %s" % (fruit1, fruit2) However, I don't want order to matter -- for example I am considering apple#1-apple#2 equivalent to apple#2-apple#1. What's the easiest way to code this? I'm thinking about making a counter in the second loop to track the second basket and not starting from the point-zero in the second loop every time.

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  • different for loops java

    - by Ayrton
    I'm having some difficulties with the following problem: I'm making a little game where you're at a specific spot and each spot has each some possible directions. The available directions are N(ord),E(ast),S,W . I use the function getPosDirections to get the possible directions of that spot. The function returns the directions into an ArrayList<String> e.g. for spot J3: [E,W] Now the game goes like this: 2 dice will be rolled so you get a number between 2 and 12, this number represents the number of steps you can make. What I want is an ArrayList of all the possible routes e.g.: I throw 3 and I'm currently at spot J3: [[E,N,E],[E,N,S],[E,S,E],[E,S,S],[W,N,E],[W,N,S],[W,S,E],[W,S,S]] How would obtain the last mentioned Array(list)?

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  • For loops in Matlab

    - by seidel
    I run through a for loop, each time extracting certain elements of an array, say element1, element2, etc. How do I then pool all of the elements I've extracted together so that I have a list of them?

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  • WinForm And Looping

    - by Soo
    I have a WinForm set up and a process that loops until a button is pressed on the form. When I try to run my code, the form does not even display. I suspect this is because the code gets stuck in the loop and doesn't get far enough to display the WinForm. How can I get the form to display and the loop to run after that point?

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  • Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

    - by theFunkyEngineer
    I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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  • Script stops while waiting for user input from STDIN.gets

    - by bob c
    I'm trying to do something like this, where I have two loops going in seperate threads. The problem I am having is that in the main thread, when I use gets and the script is waiting for user input, the other thread is stopped to wait as well. class Server def initialize() @server = TCPServer.new(8080) run end def run() @thread = Thread.new(@server) { |server| while true newsock = server.accept puts "some stuff after accept!" next if !newsock # some other stuff end } end end def processCommand() # some user commands here end test = Server.new while true do processCommand(STDIN.gets) end The above is just a sample of what I want to do. Is there a way to make the main thread block while waiting for user input?

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  • javascript callback after loop

    - by RobertPitt
    Hey guys, Iv'e just started a new Wordpress blog and i have started to build the JavaScript base! the issue im having is funnction a fucntion that loops several variables and includes the required JS libraries, what i need to do is execute the callback when the loop is finished! Heres my code! var Utilities = { Log : function(item) { if(console && typeof console.log == 'function') { //Chrome console.log(item); } }, LoadLibraries : function(callback) { $.each(Wordpress.required,function(i,val){ //Load the JS $.getScript(Wordpress.theme_root + '/js/plugins/' + val + '/' + val + '.js',function(){ // %/js/plugins/%/%.js Utilities.Log('library Loaded: ' + val); }); }); callback(); } } And the usage is like so! Utilities.LoadLibraries(function(){ Utilities.Log('All loaded'); }); Above you see the execution of callback() witch is being executed before the files are in the dom! i need this called at the end of every library inclusion!

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  • using array_sum() in a while loop

    - by m477
    Hi folks, I'm learning PHP. Having trouble understanding why this piece of code isn't working. In particular: why is the result of array_sum($x) (1596) greater than $cap? Perhaps I'm not understanding the nature of while loops, but it seems to me (looking at a print_r($x)), the loop should cut out a step before it actually does. <?php function fibonacci_sum($cap = 1000){ list( $cur, $nxt, $seq ) = array( 0, 1, array() ); while ( array_sum($seq) < $cap ) { $seq[] = $cur; $add = $cur + $nxt; $cur = $nxt; $nxt = $add; } return $seq; } $x = fibonacci_sum(); echo array_sum($x); ?> Any insight is appreciated. Best, matt

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