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  • Where should I initialize variables for an OO Recursive Descent Parse Tree?

    - by Vasto
    I'd like to preface this by stating that this is for a class, so please don't solve this for me. One of my labs for my cse class is creating an interpreter for a BNF that was provided. I understand most of the concepts, but I'm trying to build up my tree and I'm unsure where to initialize values. I've tried in both the constructor, and in the methods but Eclipse's debugger still only shows the left branch, even though it runs through completely. Here is my main procedure so you can get an idea of how I'm calling the methods. public class Parser { public static void main(String[] args) throws IOException { FileTokenizer instance = FileTokenizer.Instance(); FileTokenizer.main(args); Prog prog = new Prog(); prog.ParseProg(); prog.PrintProg(); prog.ExecProg(); } Now here is My Prog class: public class Prog { private DeclSeq ds; private StmtSeq ss; Prog() { ds = new DeclSeq(); ss = new StmtSeq(); } public void ParseProg() { FileTokenizer instance = FileTokenizer.Instance(); instance.skipToken(); //Skips program (1) // ds = new DeclSeq(); ds.ParseDS(); instance.skipToken(); //Skips begin (2) // ss = new StmtSeq(); ss.ParseSS(); instance.skipToken(); } I've tried having Prog() { ds = null; ss = null; } public void ParseProg() { FileTokenizer instance = FileTokenizer.Instance(); instance.skipToken(); //Skips program (1) ds = new DeclSeq(); ds.ParseDS(); ... But it gave me the same error. I need the parse tree built up so I can do a pretty print and an execute command, but like I said, I only get the left branch. Any help would be appreciated. Explanations why are even more so appreciated. Thank you, Vasto

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  • Java: Combination of recursive loops which has different FOR loop inside; Output: FOR loops indexes

    - by vvinjj
    currently recursion is fresh & difficult topic for me, however I need to use it in one of my algorithms. Here is the challenge: I need a method where I specify number of recursions (number of nested FOR loops) and number of iterations for each FOR loop. The result should show me, something simmilar to counter, however each column of counter is limited to specific number. ArrayList<Integer> specs= new ArrayList<Integer>(); specs.add(5); //for(int i=0 to 5; i++) specs.add(7); specs.add(9); specs.add(2); specs.add(8); specs.add(9); public void recursion(ArrayList<Integer> specs){ //number of nested loops will be equal to: specs.size(); //each item in specs, specifies the For loop max count e.g: //First outside loop will be: for(int i=0; i< specs.get(0); i++) //Second loop inside will be: for(int i=0; i< specs.get(1); i++) //... } The the results will be similar to outputs of this manual, nested loop: int[] i; i = new int[7]; for( i[6]=0; i[6]<5; i[6]++){ for( i[5]=0; i[5]<7; i[5]++){ for(i[4] =0; i[4]<9; i[4]++){ for(i[3] =0; i[3]<2; i[3]++){ for(i[2] =0; i[2]<8; i[2]++){ for(i[1] =0; i[1]<9; i[1]++){ //... System.out.println(i[1]+" "+i[2]+" "+i[3]+" "+i[4]+" "+i[5]+" "+i[6]); } } } } } } I already, killed 3 days on this, and still no results, was searching it in internet, however the examples are too different. Therefore, posting the programming question in internet first time in my life. Thank you in advance, you are free to change the code efficiency, I just need the same results.

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  • Elegant way for a recursive C++ template to do something different with the leaf class?

    - by Costas
    I have a C++ class template that makes an Array of pointers. This also gets typedefed to make Arrays of Arrays and so on: typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; I would like to be able to set one leaf node from another by copying the pointer so they both refer to the same Elem. But I also want to be able to set one Array (or Array of Arrays etc) from another. In this case I don't want to copy the pointers, I want to keep the arrays seperate and descend into each one until I get to the leaf node, at where I finally copy the pointers. I have code that does this (below). When you set something in an Array it calls a CopyIn method to do the copying. But because this is templated it also has to call the CopyIn method on the leaf class, which means I have to add a dummy method to every leaf class that just returns false. I have also tried adding a flag to the template to tell it whether it contains Arrays or not, and so whether to call the CopyIn method. This works fine - the CopyIn method of the leaf nodes never gets called, but it still has to be there for the compile to work! Is there a better way to do this? #include <stdio.h> class Elem { public: Elem(int v) : mI(v) {} void Print() { printf("%d\n",mI); } bool CopyIn(Elem *v) { return false; } int mI; }; template < typename T > class Array { public: Array(int size) : mB(0), mN(size) { mB = new T* [size]; for (int i=0; i<mN; i++) mB[i] = new T(mN); } ~Array() { for (int i=0; i<mN; i++) delete mB[i]; delete [] mB; } T* Get(int i) { return mB[i]; } void Set(int i, T* v) { if (! mB[i]->CopyIn(v) ) { // its not an array, so copy the pointer mB[i] = v; } } bool CopyIn(Array<T>* v) { for (int i=0; i<mN; i++) { if (v && i < v->mN ) { if ( ! mB[i]->CopyIn( v->mB[i] )) { // its not an array, so copy the pointer mB[i] = v->mB[i]; } } else { mB[i] = 0; } } return true; // we did the copy, no need to copy pointer } void Print() { for (int i=0; i<mN; i++) { printf("[%d] ",i); mB[i]->Print(); } } private: T **mB; int mN; }; typedef Array<Elem> ElemArray; typedef Array<ElemArray> ElemArrayArray; typedef Array<ElemArrayArray> ElemArrayArrayArray; int main () { ElemArrayArrayArray* a = new ElemArrayArrayArray(2); ElemArrayArrayArray* b = new ElemArrayArrayArray(3); // In this case I need to copy the pointer to the Elem into the ElemArrayArray a->Get(0)->Get(0)->Set(0, b->Get(0)->Get(0)->Get(0)); // in this case I need go down through a and b until I get the to Elems // so I can copy the pointers a->Set(1,b->Get(2)); b->Get(0)->Get(0)->Get(0)->mI = 42; // this will also set a[0,0,0] b->Get(2)->Get(1)->Get(1)->mI = 96; // this will also set a[1,1,1] // should be 42,2, 2,2, 3,3, 3,96 a->Print(); }

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  • PCRE (recursive) pattern that matches a string containing a correctly parenthesized substring. Why d

    - by Anton N. Petrov
    Well, there are other ways (hmmm... or rather working ways) to do it, but the question is why does this one fail? / \A # start of the string ( # group 1 (?: # group 2 [^()]* # something other than parentheses (greedy) | # or \( (?1) \) # parenthesized group 1 ) # -group 2 + # at least once (greedy) ) # -group 1 \Z # end of the string /x Fails to match a string with nested parentheses: "(())"

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  • How to handle recursive parent/child problems like this?

    - by lsdude
    In web dev I come across these problems a lot. For example, we have a giant list of URLs that are in this format: /businesses /businesses/food /businesses/food/wendys /businesses/food/wendys/chili /businesses/food/wendys/fries /businesses/food/wendys/chicken-nuggets /businesses/pharmacy/cvs /businesses/pharmacy/cvs/toothpaste /businesses/pharmacy/cvs/toothpaste/brand ... and then we need to output each one, where the parent category is in h1 tags, the child is in h2 tags, and the children of that are in h3 tags. I can handle this but I feel my code is messy. I'm sure there is a design pattern I can use? Langs are ruby/php usually. how would you handle this?

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  • Returning a list in this recursive coi function in python.

    - by Nate
    Hello. I'm having trouble getting my list to return in my code. Instead of returning the list, it keeps returning None, but if I replace the return with print in the elif statement, it prints the list just fine. How can I repair this? def makeChange2(amount, coinDenomination, listofcoins = None): #makes a list of coins from an amount given by using a greedy algorithm coinDenomination.sort() #reverse the list to make the largest position 0 at all times coinDenomination.reverse() #assigns list if listofcoins is None: listofcoins = [] if amount >= coinDenomination[0]: listofcoins = listofcoins + [coinDenomination[0]] makeChange2((amount - coinDenomination[0]), coinDenomination, listofcoins) elif amount == 0: return listofcoins else: makeChange2(amount, coinDenomination[1:], listofcoins)

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  • How do I make a recursive list that checks company rankings?

    - by Sera
    I have a set of companies in rank order. I want my rule to check if the companies in a specified list are in rank order, and for the rule to recur until all companies in the list have been checked. I currently have the following: isOrder([]). isOrder([COM1,COM2|T]) :- rank(COM1,D), rank(COM2,E), D<E, print("in order"), isOrder([COM2|T]). However, this does not seem to work. Sometimes, the recursion goes on forever without ending, and sometimes the recursion doesn't work at all. This is when I vary the code to try and get the correct answer. Can anybody help me? I have just started Prolog and my understanding of it is severely limited. Any help would be greatly appreciated.

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  • Why can't i define recursive variable in code block?

    - by senia
    Why can't i define a variable recursively in a code block? scala> { | val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} | } <console>:9: error: forward reference extends over definition of value fibs val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} ^ scala> val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} fibs: Stream[Int] = Stream(1, ?) lazy keyword solves this problem, but i can't understand why it works without a code block but throws a compilation error in a code block.

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  • Can somebody please explain this recursive function for me?

    - by capncoolio
    #include <stdio.h> #include <stdlib.h> void reprint(char *a[]) { if(*a) { printf("%d ",a); reprint(a+1); printf("%s ",*a); } } int main() { char *coll[] = {"C", "Objective", "like", "don't", "I", NULL}; reprint(coll); printf("\n"); return EXIT_SUCCESS; } As the more experienced will know, this prints the array in reverse. I don't quite understand how! I need help understanding what reprint(char *a[]) does. I understand pointer arithmetic to a degree, but from inserting printf's here and there, I've determined that the function increments up to the array end, and then back down to the start, only printing on the way down. However, I do not understand how it does this; all I've managed to understand by looking at the actual code is that if *a isn't NULL, then call reprint again, at the next index. Thanks guys!

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  • How to make a recursive onClickListener for expanding and collapsing?

    - by hunterp
    In plain english, I have a textview, and when I click on it I want it to expand, and when I click on it again, I want it to compress. How can I do this? I've tried the below, but it warns on the final line about expander might not be initialized on holderFinal.text.setOnClickListener(expander); So now the code: final View.OnClickListener expander = new View.OnClickListener() { @Override public void onClick(View v) { holderFinal.text.setText(textData); holderFinal.text.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { holderFinal.text.setText(shortText); holderFinal.text.setOnClickListener(expander); } }); } };

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  • prolog. recursive function returning multiple values.

    - by obtur
    I am new in Prolog. I need to declare a function which looks at a list like [[1, 0, 0], [1, 0, 0], [1, 0, 0]] and if the value is 0 returns its address(by considering it as a double array). I wrote a function basicly in the format: function(..., X) :- function(called by other values). How can I write a function, that returns a value when each times it called(recursively). May I get them (in above question) as alternative X's???

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  • Is it good to create a usercontrol for Recursive code in xaml?

    - by user281947
    <Border BorderBrush="#C4C8CC" BorderThickness="0,0,0,1"> <TextBlock x:Name="SectionTitle" FontFamily="Trebuchet MS" FontSize="14" FontWeight="Bold" Foreground="#3D3D3D" /> </Border> I have to use the same above format at many places in a single xaml page, so for this i created a usercontrol and defined the above code inside it. So my question is, What i am doing is it right approach? Will it make the page to load slower then the above code used as it is without defining it in a new user control?

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  • How do I construct a more complex single LINQ to XML query?

    - by Cyberherbalist
    I'm a LINQ newbie, so the following might turn out to be very simple and obvious once it's answered, but I have to admit that the question is kicking my arse. Given this XML: <measuresystems> <measuresystem name="SI" attitude="proud"> <dimension name="mass" dim="M" degree="1"> <unit name="kilogram" symbol="kg"> <factor name="hundredweight" foreignsystem="US" value="45.359237" /> <factor name="hundredweight" foreignsystem="Imperial" value="50.80234544" /> </unit> </dimension> </measuresystem> </measuresystems> I can query for the value of the conversion factor between kilogram and US hundredweight using the following LINQ to XML, but surely there is a way to condense the four successive queries into a single complex query? XElement mss = XElement.Load(fileName); IEnumerable<XElement> ms = from el in mss.Elements("measuresystem") where (string)el.Attribute("name") == "SI" select el; IEnumerable<XElement> dim = from e2 in ms.Elements("dimension") where (string)e2.Attribute("name") == "mass" select e2; IEnumerable<XElement> unit = from e3 in dim.Elements("unit") where (string)e3.Attribute("name") == "kilogram" select e3; IEnumerable<XElement> factor = from e4 in unit.Elements("factor") where (string)e4.Attribute("name") == "pound" && (string)e4.Attribute("foreignsystem") == "US" select e4; foreach (XElement ex in factor) { Console.WriteLine ((string)ex.Attribute("value")); }

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  • Advanced Django query with subselects and custom JOINS

    - by Bryan Ward
    I have been investigating this number theoretic function (found in the Height model) and I need to query for things based on the prime factorization of the primary key, or id. I have created a model for Factors of the id which maintains all of the prime factors. class Height(models.Model): b = models.IntegerField(null=True, blank=True) c = models.IntegerField(null=True, blank=True) d = models.FloatField(null=True, blank=True) class Factors(models.Model): height = models.ForeignKey(Height, null=True, blank=True) factor = models.IntegerField(null=True, blank=True) degree = models.IntegerField(null=True, blank=True) prime_id = models.IntegerField(null=True, blank=True) For example, if id=24, then the associated entries in the factors table would be height_id=24,factor=2,degree=3,prime_id=0 height_id=24,factor=3,degree=1,prime_id=1 the prime_id keep track of the relative order of the primes. Now let p < q < r < s all be prime numbers and a,b,c,d be positive integers. Then I want to be able to query for all Heights of the form id=(p**a)*(q**b)*(r**c)*(s**d). Now this is simple in the case that all of p,q,r,s,a,b,c,d are known in that I can just run Height.objects.get(id=(p**a)*(q**b)*(r**c)*(s**d)) But I need to be able to query for something like (2**a)*(3**2)*(r**c)*(s**d) where r,s,a,d are unknown and all Heights of such form will be returned. Furthermore, not all of the rows in Height will have exactly four prime factors, so I need to make sure that I am not matching rows of the form id=(p**a)*(q**b)*(r**c)*(s**d)*(t**e)... From what I can tell, the following MySQL query accomplishes this, but I would like to do it through the Django ORM. I also don't know if this MySQL query is the proper way to go about doing things. SELECT h.*,count(f.height_id) AS factorsCount FROM height AS h LEFT JOIN factors AS f ON ( f.height_id = h.id AND f.height_id IN (SELECT height_id FROM factors where prime_id=1 AND factor=2 AND degree=1) AND f.height_id IN (SELECT height_id FROM factors where prime_id=2 AND factor=3 AND degree=2) AND f.height_id IN (SELECT height_id FROM factors where prime_id=3 AND factor=5 AND degree=1) AND f.height_id IN (SELECT height_id FROM factors where prime_id=4 AND factor=7 ANd degree=1) ) GROUP BY h.id HAVING factorsCount=4 ORDER BY h.id; Any ideas or suggestions for things to try?

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  • getting Cannot identify image file when trying to create thumbnail in django

    - by Mo J. Mughrabi
    Am trying to create a thumbnail in django, am trying to build a custom class specifically to be used for generating thumbnails. As following from StringIO import StringIO from PIL import Image class Thumbnail(object): source = '' size = (50, 50) output = '' def __init__(self): pass @staticmethod def load(src): self = Thumbnail() self.source = src return self def generate(self, size=(50, 50)): if not isinstance(size, tuple): raise Exception('Thumbnail class: The size parameter must be an instance of a tuple.') self.size = size # resize properties box = self.size factor = 1 fit = True image = Image.open(self.source) # Convert to RGB if necessary if image.mode not in ('L', 'RGB'): image = image.convert('RGB') while image.size[0]/factor > 2*box[0] and image.size[1]*2/factor > 2*box[1]: factor *=2 if factor > 1: image.thumbnail((image.size[0]/factor, image.size[1]/factor), Image.NEAREST) #calculate the cropping box and get the cropped part if fit: x1 = y1 = 0 x2, y2 = image.size wRatio = 1.0 * x2/box[0] hRatio = 1.0 * y2/box[1] if hRatio > wRatio: y1 = int(y2/2-box[1]*wRatio/2) y2 = int(y2/2+box[1]*wRatio/2) else: x1 = int(x2/2-box[0]*hRatio/2) x2 = int(x2/2+box[0]*hRatio/2) image = image.crop((x1,y1,x2,y2)) #Resize the image with best quality algorithm ANTI-ALIAS image.thumbnail(box, Image.ANTIALIAS) # save image to memory temp_handle = StringIO() image.save(temp_handle, 'png') temp_handle.seek(0) self.output = temp_handle return self def get_output(self): return self.output.read() the purpose of the class is so i can use it inside different locations to generate thumbnails on the fly. The class works perfectly, I've tested it directly under a view.. I've implemented the thumbnail class inside the save method of the forms to resize the original images on saving. in my design, I have two fields for thumbnails. I was able to generate one thumbnail, if I try to generate two it crashes and I've been stuck for hours not sure whats the problem. Here is my model class Image(models.Model): article = models.ForeignKey(Article) title = models.CharField(max_length=100, null=True, blank=True) src = models.ImageField(upload_to='publication/image/') r128 = models.ImageField(upload_to='publication/image/128/', blank=True, null=True) r200 = models.ImageField(upload_to='publication/image/200/', blank=True, null=True) uploaded_at = models.DateTimeField(auto_now=True) Here is my forms class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) file = Thumbnail.load(instance.src) instance.r128 = SimpleUploadedFile( instance.src.name, file.generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, file.generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance the strange part is, when i remove the line which contains instance.r200 in the form save. It works fine, and it does the thumbnail and stores it successfully. Once I add the second thumbnail it fails.. Any ideas what am doing wrong here? Thanks Update: I tried earlier doing the following but I still got the same error class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) instance.r128 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance

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  • crash when using wireless network

    - by Erik
    ubuntu 12.04 32 bit When I start up my system almost instantly freezes, I found that the problem lays with my wireless network, because the crash is always t the same time as the message that tells me I am connected to a network when I start up connected to a cable everything works fine, I can even see that I am connected to our wireless network, until I unplug the ethernet cable, then it all freezes again the same happened when I boot from a live cd (from usb) The problem only occurs on my netbook, my laptop doesn't give any problems. I don't know if anyone else has had similar problems, or if anyone knows a solution... Thanks in advance! greetings Erik EDIT (21/3/2012): it seems there is some external factor involved, I'm using my netbook for about 50 minutes now while connected to the wireless network, and still it didn't crash strange enough, before these 50 minutes I had to put it down by holding the power button, because I decided to try it again, that time it did crash... before (while connected with an ethernet cable) I've been trying to get my Bluetooth working, that didn't succeed entirely, but I guess that might be a factor in the question why it doesn't crash at the moment now I rebooted, connected, and no crash... if it crashes again, I'll update this post again. in the meantime, if anyone has an idea on what could be a factor, and on how to create a crash using that factor, feel free to ask!

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  • Compiling Gnucash 2.6.3 in Ubuntu 14.04

    - by wolveryn
    Downloaded the debian file from source forge and followed instructions, where these errors appear, I re-downloaded the file several times with same error. I want to install the latest Gnucash not the one available on software center. Thank you for your support. /qof/gnc-date/qof print date dmy buff: There are some differences between distros in the way they namelocales, and this can cause trouble with the locale-basedformatting. If you get the assert in this function, run locale -aand make sure that en_US, en_GB, and fr_FR are installed and thatif a suffix is needed it's in the suffixes array.** ERROR:test-gnc-date.c:465:test_gnc_setlocale: code should not be reached FAIL GTester: last random seed: R02Sd8d3d0e67be954baa8ec75d81a14c0e3 /bin/bash: line 1: 18889 Terminated MALLOC_CHECK_=2 MALLOC_PERTURB_=$((${RANDOM:-256} % 256)) gtester --verbose test-qof make[5]: *** [test-nonrecursive] Error 143 make[5]: Leaving directory `/home/ahmed/gnucash/gnucash-2.6.3/src/libqof/qof/test' make[4]: *** [check-am] Error 2 make[4]: Leaving directory `/home/ahmed/gnucash/gnucash-2.6.3/src/libqof/qof/test' make[3]: *** [check-recursive] Error 1 make[3]: Leaving directory `/home/ahmed/gnucash/gnucash-2.6.3/src/libqof/qof' make[2]: *** [check-recursive] Error 1 make[2]: Leaving directory `/home/ahmed/gnucash/gnucash-2.6.3/src/libqof' make[1]: *** [check-recursive] Error 1 make[1]: Leaving directory `/home/ahmed/gnucash/gnucash-2.6.3/src' make: *** [check-recursive] Error 1

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  • Can I trust the Basic schedule equation?

    - by Steve Campbell
    I've been reading Steve McConnell's demystifying the black art of estimating book, and he gives an equation for estimating nominal schedule based on Person-months of effort: ScheduleInMonths = 3.0 x EffortInMonths ^ (1/3) Per the book, this is very accurate (within 25%), although the 3.0 factor above varies depending on your organization (typically between 2 and 4). It is supposedly easy to use historical projects in your organization to derive an appropriate factor for your use. I am trying to reconcile the equation against Agile methods, using 2-6 week cycles which are often mini-projects that have a working deliverable at the end. If I have a team of 5 developers over 4 weeks (1 month), then EffortInMonths = 5 Person Months. The algorithm then outputs a schedule of 3.0 x 5^(1/3) = 5 months. 5 months is much more than 25% different than 1 month. If I lower the 3.0 factor to 0.6, then the algorthim works (outputs a schedule of approx 1 month). The lowest possible factor mentioned in the book through is 2.0. Whats going on here? I want to trust this equation for estimating a "traditional" non-agile project, but I cannot trust it when it does not reconcile with my (agile) experience. Can someone help me understand?

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  • Mr Flibble: As Seen Through a Lens, Darkly

    - by Phil Factor
    One of the rewarding things about getting involved with Simple-Talk has been in meeting and working with some pretty daunting talents. I’d like to say that Dom Reed’s talents are at the end of the visible spectrum, but then there is Richard, who pops up on national radio occasionally, presenting intellectual programs, Andrew, master of the ukulele, with his pioneering local history work, and Tony with marathon running and his past as a university lecturer. However, Dom, who is Red Gate’s head of creative design and who did the preliminary design work for Simple-Talk, has taken the art photography to an extreme that was impossible before Photoshop. He’s not the first person to take a photograph of himself every day for two years, but he is definitely the first to weave the results into a frightening narrative that veers from comedy to pathos, using all the arts of Photoshop to create a fictional character, Mr Flibble.   Have a look at some of the Flickr pages. Uncle Spike The B-Men – Woolverine The 2011 BoyZ iN Sink reunion tour turned out to be their last Error 404 – Flibble not found Mr Flibble is not a normal type of alter-ego. We generally prefer to choose bronze age warriors of impossibly magnificent physique and stamina; superheroes who bestride the world, scorning the forces of evil and anarchy in a series noble and righteous quests. Not so Dom, whose Mr Flibble is vulnerable, and laid low by an addiction to toxic substances. His work has gained an international cult following and is used as course material by several courses in photography. Although his work was for a while ignored by the more conventional world of ‘art’ photography they became famous through the internet. His photos have received well over a million views on Flickr. It was definitely time to turn this work into a book, because the whole sequence of images has its maximum effect when seen in sequence. He has a Kickstarter project page, one of the first following the recent UK launch of the crowdfunding platform. The publication of the book should be a major event and the £45 I shall divvy up will be one of the securest investments I shall ever make. The local news in Cambridge picked up on the project and I can quote from the report by the excellent Cabume website , the source of Tech news from the ‘Cambridge cluster’ Put really simply Mr Flibble likes to dress up and take pictures of himself. One of the benefits of a split personality, however is that Mr Flibble is supported in his endeavour by Reed’s top notch photography skills, supreme mastery of Photoshop and unflinching dedication to the cause. The duo have collaborated to take a picture every day for the past 730-plus days. It is not a big surprise that neither Mr Flibble nor Reed watches any TV: In addition to his full-time role at Cambridge software house,Red Gate Software as head of creativity and the two to five hours a day he spends taking the Mr Flibble shots, Reed also helps organise the . And now Reed is using Kickstarter to see if the world is ready for a Mr Flibble coffee table book. Judging by the early response it is. At the time of writing, just a few days after it went live, ‘I Drink Lead Paint: An absurd photography book by Mr Flibble’ had raised £1,545 of the £10,000 target it needs to raise by the Friday 30 November deadline from 37 backers. Following the standard Kickstarter template, Reed is offering a series of rewards based on the amount pledged, ranging from a Mr Flibble desktop wallpaper for pledges of £5 or more to a signed copy of the book for pledges of £45 or more, right up to a starring role in the book for £1,500. Mr Flibble is unquestionably one of the more deranged Kickstarter hopefuls, but don’t think for a second that he doesn’t have a firm grasp on the challenges he faces on the road to immortalisation on 150 gsm stock. Under the section ‘risks and challenges’ on his Kickstarter page his statement begins: “An angry horde of telepathic iguanas discover the world’s last remaining stock of vintage lead paint and hold me to ransom. Gosh how I love to guzzle lead paint. Anyway… faced with such brazen bravado, I cower at the thought of taking on their combined might and die a sad and lonely Flibble deprived of my one and only true liquid love.” At which point, Reed manages to wrestle away the keyboard, giving him the opportunity to present slightly more cogent analysis of the obstacles the project must still overcome. We asked Reed a few questions about Mr Flibble’s Kickstarter adventure and felt that his responses were worth publishing in full: Firstly, how did you manage it – holding down a full time job and also conceiving and executing these ideas on a daily basis? I employed a small team of ferocious gerbils to feed me ideas on a daily basis. Whilst most of their ideas were incomprehensibly rubbish and usually revolved around food, just occasionally they’d give me an idea like my B-Men series. As a backup plan though, I found that the best way to generate ideas was to actually start taking photos. If I were to stand in front of the camera, pull a silly face, place a vegetable on my head or something else equally stupid, the resulting photo of that would typically spark an idea when I came to look at it. Sitting around idly trying to think of an idea was doomed to result in no ideas. I admit that I really struggled with time. I’m proud that I never missed a day, but it was definitely hard when you were late from work, tired or doing something socially on the same day. I don’t watch TV, which I guess really helps, because I’d frequently be spending 2-5 hours taking and processing the photos every day. Are there any overlaps between software development and creative thinking? Software is an inherently creative business and the speed that it moves ensures you always have to find solutions to new things. Everyone in the team needs to be a problem solver. Has it helped me specifically with my photography? Probably. Working within teams that continually need to figure out new stuff keeps the brain feisty I suppose, and I guess I’m continually exposed to a lot of possible sources of inspiration. How specifically will this Kickstarter project allow you to test the commercial appeal of your work and do you plan to get the book into shops? It’s taken a while to be confident saying it, but I know that people like the work that I do. I’ve had well over a million views of my pictures, many humbling comments and I know I’ve garnered some loyal fans out there who anticipate my next photo. For me, this Kickstarter is about seeing if there’s worth to my work beyond just making people smile. In an online world where there’s an abundance of freely available content, can you hope to receive anything from what you do, or would people just move onto the next piece of content if you happen to ask for some support? A book has been the single-most requested thing that people have asked me to produce and it’s something that I feel would showcase my work well. It’s just hard to convince people in the publishing industry just now to take any kind of risk – they’ve been hit hard. If I can show that people would like my work enough to buy a book, then it sends a pretty clear picture that publishers might hear, or it gives me the confidence enough to invest in myself a bit more – hard to do when you’re riddled with self-doubt! I’d love to see my work in the shops, yes. I could see it being the thing that someone flips through idly as they’re Christmas shopping and recognizing that it’d be just the perfect gift for their difficult to buy for friend or relative. That said, working in the software industry means I’m clearly aware of how I could use technology to distribute my work, but I can’t deny that there’s something very appealing to having a physical thing to hold in your hands. If the project is successful is there a chance that it could become a full-time job? At the moment that seems like a distant dream, as should this be successful, there are many more steps I’d need to take to reach any kind of business viability. Kickstarter seems exactly that – a way for people to help kick start me into something that could take off. If people like my work and want me to succeed with it, then taking a look at my Kickstarter page (and hopefully pledging a bit of support) would make my elbows blush considerably. So there is is. An opportunity to open the wallet just a bit to ensure that one of the more unusual talents sees the light in the format it deserves.  

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  • Ada and 'The Book'

    - by Phil Factor
    The long friendship between Charles Babbage and Ada Lovelace created one of the most exciting and mysterious of collaborations ever to have resulted in a technological breakthrough. The fireworks that created by the collision of two prodigious mathematical and creative talents resulted in an invention, the Analytical Engine, which went on to change society fundamentally. However, beyond that, we just don't know what the bulk of their collaborative work was about:;  it was done in strictest secrecy. Even the known outcome of their friendship, the first programmable computer, was shrouded in mystery. At the time, nobody, except close friends and family, had any idea of Ada Byron's contribution to the invention of the ‘Engine’, and how to program it. Her great insight was published in August 1843, under the initials AAL, standing for Ada Augusta Lovelace, her title then being the Countess of Lovelace. It was contained in a lengthy ‘note’ to her translation of a publication that remains the best description of Babbage's amazing Analytical Engine. The secret identity of the person behind those enigmatic initials was finally revealed by Prince de Polignac who, seventy years later, wrote to Ada's daughter to seek confirmation that her mother had, indeed, been the author of the brilliant sentences that described so accurately how Babbage's mechanical computer could be programmed with punch-cards. L.F. Menabrea's paper on the Analytical Engine first appeared in the 'Bibliotheque Universelle de Geneve' in October 1842, and Ada translated it anonymously for Taylor's 'Scientific Memoirs'. Charles Babbage was surprised that she had not written an original paper as she already knew a surprising amount about the way the machine worked. He persuaded her to at least write some explanatory notes. These notes ended up extending to four times the length of the original article and represented the first published account of how a machine could be programmed to perform any calculation. Her example of programming the Bernoulli sequence would have worked on the Analytical engine had the device’s construction been completed, and gave Ada an unassailable claim to have invented the art of programming. What was the reason for Ada's secrecy? She was the only legitimate child of Lord Byron, who was probably the best known celebrity of the age, so she was already famous. She was a senior aristocrat, with titles, a fortune in money and vast estates in the Midlands. She had political influence, and was the cousin of Lord Melbourne, who was the Prime Minister at that time. She was friendly with the young Queen Victoria. Her mathematical activities were a pastime, and not one that would be considered by others to be in keeping with her roles and responsibilities. You wouldn't dare to dream up a fictional heroine like Ada. She was dazzlingly beautiful and talented. She could speak several languages fluently, and play some musical instruments with professional skill. Contemporary accounts refer to her being 'accomplished in science, art and literature'. On top of that, she was a brilliant mathematician, a talent inherited from her mother, Annabella Milbanke. In her mother's circle of literary and scientific friends was Charles Babbage, and Ada's friendship with him dates from her teenage zest for Mathematics. She was one of the first people he'd ever met who understood what he had attempted to achieve with the 'Difference Engine', and with whom he could converse as intellectual equals. He arranged for her to have an education from the most talented academics in the country. Ada melted the heart of the cantankerous genius to the point that he became a faithful and loyal father-figure to her. She was one of the very few who could grasp the principles of the later, and very different, ‘Analytical Engine’ which was designed from the start to tackle a variety of tasks. Sadly, Ada Byron's life ended less than a decade after completing the work that assured her long-term fame, in November 1852. She was dying of cancer, her gambling habits had caused her to run up huge debts, she'd had more than one affairs, and she was being blackmailed. Her brilliant but unempathic mother was nursing her in her final illness, destroying her personal letters and records, and repaying her debts. Her husband was distraught but helpless. Charles Babbage, however, maintained his steadfast paternalistic friendship to the end. She appointed her loyal friend to be her executor. For years, she and Babbage had been working together on a secret project, known only as 'The Book'. We have a clue to what it was in a letter written by her nine years earlier, on 11th August 1843. It was a joint project by herself and Lord Lovelace, her husband, and was intended to involve Babbage's 'undivided energies'. It involved 'consulting your Engine' (it required Babbage’s computer). The letter gives no hint about the project except for the high-minded nature of its purpose, and its highly mathematical nature.  From then on, the surviving correspondence between the two gives only veiled references to 'The Book'. There isn't much, since Babbage later destroyed any letters that could have damaged her reputation within the Establishment. 'I cannot spare the book today, which I am very sorry for. At the moment I want it for constant reference, but I think you can have it tomorrow' (Oct 1844)  And 'I will send you the book directly, and you can say, when you receive it, how long you will want to keep it'. (Nov 1844)  The two of them were obviously intent on the work: She writes, four years later, 'I have an engagement for Wednesday which will prevent me from attending to your wishes about the book' (Dec 1848). This was something that they both needed to work on, but could not do in parallel: 'I will send the book on Tuesday, and it can be left with you till Friday' (11 Feb 1849). After six years work, it had been so well-handled that it was beginning to fall apart: 'Don't forget the new cover you promised for the book. The poor book is very shabby and wants one' (20 Sept 1849). So what was going on? The word 'book' was not a code-word: it was a real book, probably a 'printer's blank', plain paper, but properly bound so printers and publishers could show off how the published work might look. The hints from the correspondence are of advanced mathematics. It is obvious that the book was travelling between them, back and forth, each one working on it for less than a week before passing it back. Ada and her husband were certainly involved in gambling large sums of money on the horses, and so most biographers have concluded that the three of them were trying to calculate the mathematical odds on the horses. This theory has three large problems. Firstly, Ada's original letter proposing the project refers to its high-minded nature. Babbage was temperamentally opposed to gambling and would scarcely have given so much time to the project, even though he was devoted to Ada. Secondly, Babbage would have very soon have realized the hopelessness of trying to beat the bookies. This sort of betting never attracts his type of intellectual background. The third problem is that any work on calculating the odds on horses would not need a well-thumbed book to pass back and forth between them; they would have not had to work in series. The original project was instigated by Ada, along with her husband, William King-Noel, 1st Earl of Lovelace. Charles Babbage was invited to join the project after the couple had come up with the idea. What could William have contributed? One might assume that William was a Bertie Wooster character, addicted only to the joys of the turf, but this was far from the truth. He was a scientist, a Cambridge graduate who was later elected to be a Fellow of the Royal Society. After Eton, he went to Trinity College, Cambridge. On graduation, he entered the diplomatic service and acted as secretary under Lord Nugent, who was Lord Commissioner of the Ionian Islands. William was very friendly with Babbage too, able to discuss scientific matters on equal terms. He was a capable engineer who invented a process for bending large timbers by the application of steam heat. He delivered a paper to the Institution of Civil Engineers in 1849, and received praise from the great engineer, Isambard Kingdom Brunel. As well as being Lord Lieutenant of the County of Surrey for most of Victoria's reign, he had time for a string of scientific and engineering achievements. Whatever the project was, it is unlikely that William was a junior partner. After Ada's death, the project disappeared. Then, two years later, Babbage, through one of his occasional outbursts of temper, demonstrated that he was able to decrypt one of the most powerful of secret codes, Vigenère's autokey cipher.  All contemporary diplomatic and military messages used a variant of this cipher. Babbage had made three important discoveries, namely, the mathematical law of this cipher, the principle of the key periodicity, and the technique of the symmetry of position. The technique is now known as the Kasiski examination, also called the Kasiski test, but Babbage got there first. At one time, he listed amongst his future projects, the writing of a book 'The Philosophy of Decyphering', but it never came to anything. This discovery was going to change the course of history, since it was used to decipher the Russians’ military dispatches in the Crimean war. Babbage himself played a role during the Crimean War as a cryptographical adviser to his friend, Rear-Admiral Sir Francis Beaufort of the Admiralty. This is as much as we can be certain about in trying to make sense of the bulk of the time that Charles Babbage and Ada Lovelace worked together. Nine years of intensive work, involving the 'Engine' and a great deal of mathematics and research seems to have been lost: or has it? I've argued in the past http://www.simple-talk.com/community/blogs/philfactor/archive/2008/06/13/59614.aspx that the cracking of the Vigenère autokey cipher, was a fundamental motive behind the British Government's support and funding of the 'Difference Engine'. The Duke of Wellington, whose understanding of the military significance of being able to read enemy dispatches, was the most steadfast advocate of the project. If the three friends were actually doing the work of cracking codes by mathematical techniques that used the techniques of key periodicity, and symmetry of position (the use of a book being passed quickly to and fro is very suggestive), intending to then use the 'Engine' to do the routine cracking of each dispatch, then this is a rather different story. The project was Ada and William's idea. (William had served in the diplomatic service and would be familiar with the use of codes). This makes Ada Lovelace the initiator of a project which, by giving both Britain, and probably the USA, a diplomatic and military advantage in the second part of the Nineteenth century, changed world history. Ada would never have wanted any credit for cracking the cipher, and developing the method that rendered all contemporary military and diplomatic ciphering techniques nugatory; quite the reverse. And it is clear from the gaps in the record of the letters between the collaborators that the evidence was destroyed, probably on her request by her irascible but intensely honorable executor, Charles Babbage. Charles Babbage toyed with the idea of going public, but the Crimean war put an end to that. The British Government had a valuable secret, and intended to keep it that way. Ada and Charles had quite often discussed possible moneymaking projects that would fund the development of the Analytic Engine, the first programmable computer, but their secret work was never in the running as a potential cash cow. I suspect that the British Government was, even then, working on the concealment of a discovery whose value to the nation depended on it remaining so. The success of code-breaking in the Crimean war, and the American Civil war, led to the British and Americans  subsequently giving much more weight and funding to the science of decryption. Paradoxically, this makes Ada's contribution even closer to the creation of Colossus, the first digital computer, at Bletchley Park, specifically to crack the Nazi’s secret codes.

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  • How to get SQL Railroad Diagrams from MSDN BNF syntax notation.

    - by Phil Factor
    pre {margin-bottom:.0001pt; font-size:8.0pt; font-family:"Courier New"; margin-left: 0cm; margin-right: 0cm; margin-top: 0cm; } On SQL Server Books-On-Line, in the Transact-SQL Reference (database Engine), every SQL Statement has its syntax represented in  ‘Backus–Naur Form’ notation (BNF)  syntax. For a programmer in a hurry, this should be ideal because It is the only quick way to understand and appreciate all the permutations of the syntax. It is a great feature once you get your eye in. It isn’t the only way to get the information;  You can, of course, reverse-engineer an understanding of the syntax from the examples, but your understanding won’t be complete, and you’ll have wasted time doing it. BNF is a good start in representing the syntax:  Oracle and SQLite go one step further, and have proper railroad diagrams for their syntax, which is a far more accessible way of doing it. There are three problems with the BNF on MSDN. Firstly, it is isn’t a standard version of  BNF, but an ancient fork from EBNF, inherited from Sybase. Secondly, it is excruciatingly difficult to understand, and thirdly it has a number of syntactic and semantic errors. The page describing DML triggers, for example, currently has the absurd BNF error that makes it state that all statements in the body of the trigger must be separated by commas.  There are a few other detail problems too. Here is the offending syntax for a DML trigger, pasted from MSDN. Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) CREATE TRIGGER [ schema_name . ]trigger_name ON { table | view } [ WITH <dml_trigger_option> [ ,...n ] ] { FOR | AFTER | INSTEAD OF } { [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] } [ NOT FOR REPLICATION ] AS { sql_statement [ ; ] [ ,...n ] | EXTERNAL NAME <method specifier [ ; ] > }   <dml_trigger_option> ::=     [ ENCRYPTION ]     [ EXECUTE AS Clause ]   <method_specifier> ::=  This should, of course, be /* Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) */ CREATE TRIGGER [ schema_name . ]trigger_name ON { table | view } [ WITH <dml_trigger_option> [ ,...n ] ] { FOR | AFTER | INSTEAD OF } { [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] } [ NOT FOR REPLICATION ] AS { {sql_statement [ ; ]} [ ...n ] | EXTERNAL NAME <method_specifier> [ ; ] }   <dml_trigger_option> ::=     [ ENCRYPTION ]     [ EXECUTE AS CLAUSE ]   <method_specifier> ::=     assembly_name.class_name.method_name I’d love to tell Microsoft when I spot errors like this so they can correct them but I can’t. Obviously, there is a mechanism on MSDN to get errors corrected by using comments, but that doesn’t work for me (*Error occurred while saving your data.”), and when I report that the comment system doesn’t work to MSDN, I get no reply. I’ve been trying to create railroad diagrams for all the important SQL Server SQL statements, as good as you’d find for Oracle, and have so far published the CREATE TABLE and ALTER TABLE railroad diagrams based on the BNF. Although I’ve been aware of them, I’ve never realised until recently how many errors there are. Then, Colin Daley created a translator for the SQL Server dialect of  BNF which outputs standard EBNF notation used by the W3C. The example MSDN BNF for the trigger would be rendered as … /* Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) */ create_trigger ::= 'CREATE TRIGGER' ( schema_name '.' ) ? trigger_name 'ON' ( table | view ) ( 'WITH' dml_trigger_option ( ',' dml_trigger_option ) * ) ? ( 'FOR' | 'AFTER' | 'INSTEAD OF' ) ( ( 'INSERT' ) ? ( ',' ) ? ( 'UPDATE' ) ? ( ',' ) ? ( 'DELETE' ) ? ) ( 'NOT FOR REPLICATION' ) ? 'AS' ( ( sql_statement ( ';' ) ? ) + | 'EXTERNAL NAME' method_specifier ( ';' ) ? )   dml_trigger_option ::= ( 'ENCRYPTION' ) ? ( 'EXECUTE AS CLAUSE' ) ?   method_specifier ::= assembly_name '.' class_name '.' method_name Colin’s intention was to allow anyone to paste SQL Server’s BNF notation into his website-based parser, and from this generate classic railroad diagrams via Gunther Rademacher's Railroad Diagram Generator.  Colin's application does this for you: you're not aware that you are moving to a different site.  Because Colin's 'translator' it is a parser, it will pick up syntax errors. Once you’ve fixed the syntax errors, you will get the syntax in the form of a human-readable railroad diagram and, in this form, the semantic mistakes become flamingly obvious. Gunter’s Railroad Diagram Generator is brilliant. To be able, after correcting the MSDN dialect of BNF, to generate a standard EBNF, and from thence to create railroad diagrams for SQL Server’s syntax that are as good as Oracle’s, is a great boon, and many thanks to Colin for the idea. Here is the result of the W3C EBNF from Colin’s application then being run through the Railroad diagram generator. create_trigger: dml_trigger_option: method_specifier:   Now that’s much better, you’ll agree. This is pretty easy to understand, and at this point any error is immediately obvious. This should be seriously useful, and it is to me. However  there is that snag. The BNF is generally incorrect, and you can’t expect the average visitor to mess about with it. The answer is, of course, to correct the BNF on MSDN and maybe even add railroad diagrams for the syntax. Stop giggling! I agree it won’t happen. In the meantime, we need to collaboratively store and publish these corrected syntaxes ourselves as we do them. How? GitHub?  SQL Server Central?  Simple-Talk? What should those of us who use the system  do with our corrected EBNF so that anyone can use them without hassle?

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