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  • Avoiding RTTI In Java

    - by destructo_gold
    Hi, If I have a superclass, say Animal, and two subclasses: Zebra and Giraffe, If I decide to define a Vector of Animals: Vector <Animal> animals = new Vector(); and I want to say: You can add Giraffes, but you must own at least one Zebra first. What is the best way to do this without using RTTI? (instanceof)

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  • Foreign key onto weak entity set in MS SQL Server 2008?

    - by Nic Waller
    I'm using Microsoft SQL Server 2008 Management Studio to create a relational schema by following an Entity-Relationship diagram. (included below; unrelated details removed) Until now, primary and foreign keys have been working as expected. But when I try to create a foreign key from the entity relationship takes onto the weak entity set section, I get an error. Section is identified by a composite primary key in the context of course, which has course_id as a primary key. Therefore, the primary key of section is a 4-way composite key. The entity relationship takes needs to refer to section, so it includes all 4 primary attributes from section in it's own primary key. When trying to establish a foreign key relationship from takes to section, Studio gives the following error: The columns in table 'section' do not match an existing primary key or UNIQUE constraint. Am I doing something wrong, or is this an unsupported configuration? I can provide more details or the SQL schema if necessary.

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  • Theory of Computation - Showing that a language is regular..

    - by Tony
    I'm reviewing some notes for my course on Theory of Computation and I'm a little bit stuck on showing the following statement and I was hoping somebody could help me out with an explanation :) Let A be a regular language. The language B = {ab | a exists in A and b does not exist in A*} Why is B a regular language? Some points are obvious to me. If b is simply a constant string, this is trivial. Since we know a is in A and b is a string, regular languages are closed under union, so unioning the language that accepts these two strings is obviously regular. I'm not sure that b is constant, however. Maybe it is, and if so, then this isn't really an issue. I'm having a hard time making sense of it. Thanks!

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  • Need help with dynamic programming problem

    - by John Retallack
    I have the following problem : I am given a tree with N apples, for each apple I am given it's weight and height,I can pick apples up to a given height H,each time I pick an apple the height of every apple is increased with U(also given).I have to find out the maximum weight of apples I can pick. e.g: N=4 H=100 U=10 (height-eight) apple1: 91 10 apple2: 82 30 apple3: 93 5 apple4: 94 15 The answer is 45 : I first pick the apple with the weight of 15 then the one with the weight of 30. I would like to know if someone here could help me with giving me an hint on how I should approach this problem. Thank you.

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  • Why isn't my operator overloading working properly?

    - by Mithrax
    I have the following Polynomial class I'm working on: #include <iostream> using namespace std; class Polynomial { //define private member functions private: int coef[100]; // array of coefficients // coef[0] would hold all coefficients of x^0 // coef[1] would hold all x^1 // coef[n] = x^n ... int deg; // degree of polynomial (0 for the zero polynomial) //define public member functions public: Polynomial::Polynomial() //default constructor { for ( int i = 0; i < 100; i++ ) { coef[i] = 0; } } void set ( int a , int b ) //setter function { //coef = new Polynomial[b+1]; coef[b] = a; deg = degree(); } int degree() { int d = 0; for ( int i = 0; i < 100; i++ ) if ( coef[i] != 0 ) d = i; return d; } void print() { for ( int i = 99; i >= 0; i-- ) { if ( coef[i] != 0 ) { cout << coef[i] << "x^" << i << " "; } } } // use Horner's method to compute and return the polynomial evaluated at x int evaluate ( int x ) { int p = 0; for ( int i = deg; i >= 0; i-- ) p = coef[i] + ( x * p ); return p; } // differentiate this polynomial and return it Polynomial differentiate() { if ( deg == 0 ) { Polynomial t; t.set ( 0, 0 ); return t; } Polynomial deriv;// = new Polynomial ( 0, deg - 1 ); deriv.deg = deg - 1; for ( int i = 0; i < deg; i++ ) deriv.coef[i] = ( i + 1 ) * coef[i + 1]; return deriv; } Polynomial Polynomial::operator + ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator += ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator *= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator * ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); return c; } }; int main() { Polynomial a, b, c, d; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; c = a * b; // (7x^4 + x^2) * (6x^3 - 3x^2) c.print(); cout << "\n"; d = c.differentiate().differentiate(); d.print(); cout << "\n"; cout << c.evaluate ( 2 ); //substitue x with 2 cin.get(); } Now, I have the "-" operator overloaded and it works fine: Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } However, I'm having difficulty with my "-=" operator: Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); // overwrite value of 'a' with the newly computed 'c' before returning 'a' for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } I just slightly modified my "-" operator method to overwrite the value in 'a' and return 'a', and just use the 'c' polynomial as a temp. I've put in some debug print statement and I confirm that at the time of computation, both: c = a - b; and a -= b; are computed to the same value. However, when I go to print them, their results are different: Polynomial a, b; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; Result: 7x^4 -6x^3 4x^2 7x^4 1x^2 Why is my c = a - b and a -= b giving me different results when I go to print them?

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  • How do I work out IEEE 754 64-bit Floating Point Double Precision?

    - by yousef gassar
    enter code herehello i have done it in 32 but i could dont do it in 62bits please i need help I am stuck on this question and need help. I don't know how to work it out. This is the question. Below are two numbers represented in IEEE 754 64-bit Floating Point Double Precision, the bias of the signed exponent is -1023. Any particular real number ‘N’ represented in 64-bit form (i.e. with the following bit fields; 1-bit Sign, 11-bit Exponent, 52-bit Fraction) can be expressed in the form ±1.F2 × 2X by substituting the bit-field values using formula (IV.I): N = (-1) S × 1.F2 × 2(E – 1023) for 0 < E < 2047.........................….(IV.I) Where N= the number represented, S=Sign bit-value, E=Exponent=X +1023, F=Fraction or Mantissa are the values in the 1, 11 and 52-bit fields respectively in the IEEE 754 64-bit FP representation. Using formula (IV.I), express the 64-bit FP representation of each number as: (i) A binary number of the form:- ±1.F2 × 2X (ii) A decimal number of the form:- ±0.F10 × 10Y {limit F10 to 10 decimal places} Sign 0 1 Exponent 1000 0001 001 11 Fraction 1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 52 Sign 1 1 Exponent 1000 0000 000 11 Fraction 1001 0010 0001 1111 1011 0101 0100 0100 0100 0010 1101 0001 1000 52 I know I have to use the formula for each of the these but how do I work it out? Is it like this? N = (-1) S × 1.F2 × 2(E – 1023) = 1 x 1.1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 x 1000 0001 00111 (-1023)?

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  • Diophantine Equation

    - by lakshmi
    Show that it is possible to buy exactly 50, 51, 52, 53, 54, and 55 McNuggets, by finding solutions to the Diophantine equation. You can solve this in your head, using paper and pencil, or writing a program. However you chose to solve this problem, list the combinations of 6, 9 and 20 packs of McNuggets you need to buy in order to get each of the exact amounts. Given that it is possible to buy sets of 50, 51, 52, 53, 54 or 55 McNuggets by combinations of 6, 9 and 20 packs, show that it is possible to buy 56, 57,..., 65 McNuggets. In other words, show how, given solutions for 50-55, one can derive solutions for 56-65.python

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  • How to obtain dependency metrics from Java source code?

    - by Bram Schoenmakers
    For an assignment we have to extract some software metrics from the Hibernate project. We have to extract the afferent coupling and efferent coupling metrics (dependency fan-in, fan-out) from each revision of each package in Hibernate. Some tools were provided which are able to extract these metrics, such as ckjm and JDepend. Other tools I have checked were Sonar, javancss and AOP. There is also the Metrics Eclipse plugin which I didn't get to work either. What these tools have in common, as far as I can see, is that they all operate on bytecode (*.class files). This is a problem, because I have to build every revision from source in order to run, say, JDepend on it. Older revisions won't build because my development stack is too recent. What I would like to do is to do this kind of analysis on source files so that I don't have to build each revision. Is this possible? Or is there a good reason why all these tools only operate on bytecode?

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  • HttpURLConnection timeout question

    - by Malachi
    I want to return false if the URL takes more then 5 seconds to connect - how is this possible using java? Here is the code I am using to check if the URL is valid HttpURLConnection.setFollowRedirects(false); HttpURLConnection con = (HttpURLConnection) new URL(url).openConnection(); con.setRequestMethod("HEAD"); return (con.getResponseCode() == HttpURLConnection.HTTP_OK);

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  • IBasic Accumulator

    - by Tara
    I am trying to do an accumulator in IBasic for a college assignment and I have the general stuff down but I cannot get it to accumulate. The code is below. My question is how do I get it to accumulate and pass to the different module. I'm trying to calculate how many right answers the user gets. Also, i need to calculate the percentage of right answers. so if the user gets 9 out of 10 right theyed answer 90% right. 'October 15, 2009 ' 'Lab 7.5 Programming Challenge 1 - Average Test Scores ' 'This is a dice game ' declare main() declare inputName(name:string) declare getAnswer(num1:int, num2:int) declare getResult(num1:int, num2:int, answer:int) declare avgRight(getRight:int) declare printInfo(name:string, getRight:int, averege:float) openconsole main() do:until inkey$<>"" closeconsole end sub main() def name:string def num1, num2, answer, total, getRight:int def averege:float inputName (name) getRight = 0 For counter = 1 to 10 getRight = getAnswer(num1, num2) getRight = getRight + 1 next counter average = avgRight (getRight) printInfo(Name, getRight, average) end sub inputName (name) Input "Please enter your name: " ,name return sub getAnswer(num1, num2) def answer, getRight:int num1 = rnd (10) + 1 num2 = rnd (10) + 1 Print num1, "+ " ,num2 Input "What is the answer to the equation? " ,answer getRight = getResult(num1, num2, answer) return getRight sub getResult(num1, num2, answer) def getRight:int if answer = num1 + num2 getRight = 1 else getRight = 0 endif return getRight sub avgRight(getRight) def average:float average = getRight / 10 return average sub printInfo(name, getRight, averege) Print "The students name is: " ,name Print "The number right is: " ,getRight Print Using ("&##.#&", "The average right is " ,averege * 100, "%") return

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  • Python sudoku programming

    - by trevor
    I need your help on this. I have this program and I must finish it. It's missing 3 parts. Here is the program I'm working with: import copy def display(A): if A: for i in range(9): for j in range(9): if type(A[i][j]) == type([]): print A[i][j][0], else: print A[i][j], print print else: print A def has_conflict(A): for i in range(9): for j in range(9): for (x,y) in get_neighbors(i,j): if len(A[i][j])==1 and A[i][j]==A[x][y]: return True return False # HERE ARE THE PARTS THAT REQUIRE HELP!!!! def get_neighbors(x,y): return [] def update(A, i, j, value): return [] def solve(A): return [] # ENDS PARTS THAT REQUIRE HELP!!!! A = [] infile = open('puzzle1.txt', 'r') for i in range(9): A += [[]] for j in range(9): num = int(infile.read(2)) if num: A[i] += [[num]] else: A[i] += [[1,2,3,4,5,6,7,8,9]] for i in range(9): for j in range(9): if len(A[i][j])==1: A = update(A, i,j, A[i][j][0]) if A==[]: break if A==[]: break if A<>[]: A = solve(A) display(A) I need to solve the stuff formerly in bold letters, now explicitly marked in the code, specifically - get_neighbors(): - update(): - solve(): Thank you for your time and help.

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  • using java Calendar

    - by owca
    I have a simple task. There are two classes : Ticket and Date. Ticket contains event, event place and event date which is a Date object. I also need to provide a move() method for Date object, so I used Calendar and Calendar's add(). Everything looks fine apart of the output. I constantly get 5,2,1 as the date's day,month,year. Lines with asterix return proper date. The code : Ticket class : public class Ticket { private String what; private String where; private Date when; public Ticket(String s1, String s2, Data d){ this.what = s1; this.where = s2; this.when = d; } *public Date giveDate(){ System.out.println("when in giveDate() "+this.when); return this.when; } public String toString(){ return "what: "+this.what+"\n"+"where: "+this.where+"\n"+"when: "+this.when; } } Date class: import java.util.Calendar; import java.util.GregorianCalendar; public class Date { public int day; public int month; public int year; public Date(int x, int y, int z){ *System.out.println("x: "+x); *System.out.println("y: "+y); *System.out.println("z: "+z); this.day = x; this.month = y; this.year = z; *System.out.println("this.day: "+this.day); *System.out.println("this.month: "+this.month); *System.out.println("this.year: "+this.year); } public Date move(int p){ *System.out.println("before_change: "+this.day+","+this.month+","+this.year); Calendar gc = new GregorianCalendar(this.year, this.month, this.day); System.out.println("before_adding: "+gc.DAY_OF_MONTH+","+gc.MONTH+","+gc.YEAR); gc.add(Calendar.DAY_OF_YEAR, p); System.out.println("after_adding: "+gc.DAY_OF_MONTH+","+gc.MONTH+","+gc.YEAR); this.year = gc.YEAR; this.day = gc.DAY_OF_MONTH; this.month = gc.MONTH; return this; } @Override public String toString(){ return this.day+","+this.month+","+this.year; } } Main for testing : public class Main { public static void main(String[] args) { Date date1=new Date(30,4,2002); Ticket event1=new Ticket("Peter Gabriel's gig", "London",date1 ); Ticket event2=new Ticket("Diana Kroll's concert", "Glasgow",date1 ); Date date2=event2.giveDate(); date2.move(30); Ticket event3=new Ticket("X's B-day", "some place",date2 ); System.out.println(date1); System.out.println(event1); System.out.println(event2); System.out.println(event3); } } And here's my output. I just can't get it where 5,2,1 come from :/ x: 30 y: 4 z: 2002 this.day: 30 this.month: 4 this.year: 2002 when in giveDate() 6,12,2004 before_change: 6,12,2004 before_adding: 5,2,1 after_adding: 5,2,1 5,2,1 what: Peter Gabriel's gig where: London when: 5,2,1 (...)

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  • Update table.column with another table.column with common joined column

    - by Matt
    Hit a speed bump, trying to update some column values in my table from another table. This is what is supposed to happen when everything works Correct all the city, state entries in tblWADonations by creating an update statement that moves the zip city from the joined city/state zip field to the tblWADonations city state TBL NAME | COLUMN NAMES tblZipcodes with zip,city,State tblWADonations with zip,oldcity,oldstate This is what I have so far: UPDATE tblWADonations SET oldCity = tblZipCodes.city, oldState = tblZipCodes.state FROM tblWADonations INNER JOIN tblZipCodes ON tblWADonations.zip = tblZipCodes.zip Where oldCity <> tblZipcodes.city; There seems to be easy ways to do this online but I am overlooking something. Tried this by hand and in editor this is what it kicks back. Msg 8152, Level 16, State 2, Line 1 String or binary data would be truncated. The statement has been terminated. Please include a sql statement or where I need to make the edit so I can mark this post as a reference in my favorites. Thanks!

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  • describe class versions of primitive type data

    - by paula
    please some explain to me this.... Explain why java has class versios of primitive data types? describe the class versions of primitive java types and expain pros and cons? expalin why class versions of primitive java types are available, but why the primitive types are still frequently used? expalin how primitive and non-primitive data types are passed as parameters to methods in java and how that affects altering the value of data passed? primitve data types are: int, float, char, long, short, byte, boolean and double.

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  • C - array count, strtok, etc

    - by Pedro
    Hi... i have a little problem on my code... HI open a txt that have this: LEI;7671;Maria Albertina da silva;[email protected]; 9;8;12;9;12;11;6;15;7;11; LTCGM;6567;Artur Pereira Ribeiro;[email protected]; 6;13;14;12;11;16;14; LEI;7701;Ana Maria Carvalho;[email protected]; 8;13;11;7;14;12;11;16;14; LEI, LTCGM are the college; 7671, 6567, 7701 is student number; Maria, Artur e Ana are the students name; [email protected], ...@gmail are emails from students; the first number of every line is the total of classes that students have; after that is students school notes; example: College: LEI Number: 7671 Name: Maria Albertina da Silva email: [email protected] total of classes: 9 Classe Notes: 8 12 9 12 11 6 15 7 11. My code: typedef struct aluno{ char sigla[5];//college char numero[80];//number char nome[80];//student name char email[20];//email int total_notas;// total of classes char tot_not[40]; // total classes char notas[20];// classe notes int nota; //class notes char situacao[80]; //situation (aproved or disaproved) }ALUNO; void ordena(ALUNO*alunos, int tam)//bubble sort { int i=0; int j=0; char temp[100]; for( i=0;i<tam;i++) for(j=0;j<tam-1;j++) if(strcmp( alunos[i].sigla[j], alunos[i].sigla[j+1])>0){ strcpy(temp, alunos[i].sigla[j]); strcpy(alunos[i].sigla[j],alunos[i].sigla[j+1]); strcpy(alunos[i].sigla[j+1], temp); } } void xml(ALUNO*alunos, int tam){ FILE *fp; char linha[60];//line int soma, max, min, count;//biggest note and lowest note and students per course count float media; //media of notes fp=fopen("example.txt","r"); if(fp==NULL){ exit(1); } else{ while(!(feof(fp))){ soma=0; media=0; max=0; min=0; count=0; fgets(linha,60,fp); if(linha[0]=='L'){ if(ap_dados=strtok(linha,";")){ strcpy(alunos[i].sigla,ap_dados);//copy to struct // i need to call bubble sort here, but i don't know how printf("College: %s\n",alunos[i].sigla); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].numero,ap_dados);//copy to struct printf("number: %s\n",alunos[i].numero); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].nome, ap_dados);//copy to struct printf("name: %s\n",alunos[i].nome); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].email, ap_dados);//copy to struct printf("email: %s\n",alunos[i].email); } } } }i++; } if(isdigit(linha[0])){ if(info_notas=strtok(linha,";")){ strcpy(alunos[i].tot_not,info_notas); alunos[i].total_notas=atoi(alunos[i].tot_not);//total classes for(z=0;z<=alunos[i].total_notas;z++){ if(info_notas=strtok(NULL,";")){ strcpy(alunos[i].notas,info_notas); alunos[i].nota=atoi(alunos[i].notas); // student class notes } soma=soma + alunos[i].nota; media=soma/alunos[i].total_notas;//doesn't work if(alunos[i].nota>max){ max=alunos[i].nota;;//doesn't work } else{ if(min<alunos[i].nota){ min=alunos[i].nota;;//doesn't work } } //now i need to count the numbers of students in the same college, but doesn't work /*If(strcmp(alunos[i].sigla, alunos[i+1].sigla)=0){ count ++; printf("%d\n", count); here for LEI should appear 2 students and for LTCGM appear 1, don't work }*/ //Now i need to see if student is aproved or disaproved // Student is disaproved if he gets 3 notes under 10, how can i do that? } printf("media %d\n",media); //media printf("Nota maxima %d\n",max);// biggest note printf("Nota minima %d\n",min); //lowest note }i++; } } } fclose(fp); } int main(int argc, char *argv[]){ ALUNO alunos; FILE *fp; int tam; fp=fopen(nomeFicheiro,"r"); alunos = (ALUNO*) calloc (tam, sizeof(ALUNO)); xml(alunos,nomeFicheiro, tam); system("PAUSE"); return 0; }

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  • "Programming In Haskell" error in sat function

    - by Matt Ellen
    I'm in chapter 8 of Graham Hutton's Programming in Haskell and I'm copying the code and testing it in GHC. See the slides here: http://www.cis.syr.edu/~sueo/cis352/chapter8.pdf in particular slide 15 The relevant code I've copied so far is: type Parser a = String -> [(a, String)] pih_return :: a -> Parser a pih_return v = \inp -> [(v, inp)] failure :: Parser a failure = \inp -> [] item :: Parser Char item = \inp -> case inp of [] -> [] (x:xs) -> [(x,xs)] parse :: Parser a -> String -> [(a, String)] parse p inp = p inp sat :: (Char -> Bool) -> Parser Char sat p = do x <- item if p x then pih_return x else failure I have changed the name of the return function from the book to pih_return so that it doesn't clash with the Prelude return function. The errors are in the last function sat. I have copied this directly from the book. As you can probably see p is a function from Char to Bool (e.g. isDigit) and x is of type [(Char, String)], so that's the first error. Then pih_return takes a value v and returns [(v, inp)] where inp is a String. This causes an error in sat because the v being passed is x which is not a Char. I have come up with this solution, by explicitly including inp into sat sat :: (Char -> Bool) -> Parser Char sat p inp = do x <- item inp if p (fst x) then pih_return (fst x) inp else failure inp Is this the best way to solve the issue?

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  • Cartesian product in Scheme

    - by John Retallack
    I've been trying to do a function that returns the Cartesian Product of n sets,in Dr Scheme,the sets are given as a list of lists,I've been stuck at this all day,I would like a few guidelines as where to start,I've wrote a pice of code but it dosen't work. (define cart-n(?(l) (if (null? l) '(()) (map (?(lst) (cons (car ( car(l))) lst)) (cart-n (cdr l) )))))

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  • Exception on ExecuteReader() using OleDbCommand and Access

    - by Shane Fagan
    Hi again all, I'm getting the error below for this SQL statement in VB.Net 'Fill in the datagrid with the info needed from the accdb file 'to make it simple to access the db connstring = "Provider=Microsoft.ACE.OLEDB.12.0;Data " connstring += "Source=" & Application.StartupPath & "\AuctioneerSystem.accdb" 'make the new connection conn = New System.Data.OleDb.OleDbConnection(connstring) 'the sql command SQLString = "SELECT AllPropertyDetails.PropertyID, Street, Town, County, Acres, Quotas, ResidenceDetails, Status, HighestBid, AskingPrice FROM AllPropertyDetails " SQLString += "INNER JOIN Land ON AllPropertyDetails.PropertyID = Land.PropertyID " SQLString += "WHERE Deleted = False " If PriceRadioButton.Checked = True Then SQLString += "ORDER BY AskingPrice ASC" ElseIf AcresRadioButton.Checked = True Then SQLString += "ORDER BY Acres ASC" End If 'try to open the connection conn.Open() 'if the connection is open If ConnectionState.Open.ToString = "Open" Then 'use the sqlstring and conn to create the command cmd = New System.Data.OleDb.OleDbCommand(SQLString, conn) 'read the db and put it into dr dr = cmd.ExecuteReader If dr.HasRows Then 'if there is rows in the db then make sure the list box is clear 'clear the rows and columns if there is rows in the data grid LandDataGridView.Rows.Clear() LandDataGridView.Columns.Clear() 'add the columns LandDataGridView.Columns.Add("PropertyNumber", "Property Number") LandDataGridView.Columns.Add("Address", "Address") LandDataGridView.Columns.Add("Acres", "No. of Acres") LandDataGridView.Columns.Add("Quotas", "Quotas") LandDataGridView.Columns.Add("Details", "Residence Details") LandDataGridView.Columns.Add("Status", "Status") LandDataGridView.Columns.Add("HighestBid", "Highest Bid") LandDataGridView.Columns.Add("Price", "Asking Price") While dr.Read 'output the fields into the data grid LandDataGridView.Rows.Add( _ dr.Item("PropertyID").ToString _ , dr.Item("Street").ToString & " " & dr.Item("Town").ToString & ", " & dr.Item("County").ToString _ , dr.Item("Acres").ToString _ , dr.Item("Quota").ToString _ , dr.Item("ResidenceDetails").ToString _ , dr.Item("Status").ToString _ , dr.Item("HighestBid").ToString _ , dr.Item("AskingPrice").ToString) End While End If 'close the data reader dr.Close() End If 'close the connection conn.Close() Any ideas why its not working? The fields in the DB and the table names seem ok but its not working :/ The tables are AllPropertyDetails ProperyID:Number Street: text Town: text County: text Status: text HighestBid: Currency AskingPrice: Currency Deleted: Boolean Land PropertyID: Number Acres: Number Quotas: Text ResidenceDetails: text error is: System.InvalidOperationException was unhandled Message="An error occurred creating the form. See Exception.InnerException for details. The error is: No value given for one or more required parameters." Source="AuctioneerProject" StackTrace: at AuctioneerProject.My.MyProject.MyForms.Create__Instance__[T](T Instance) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 190 at AuctioneerProject.My.MyProject.MyForms.get_LandReport() at AuctioneerProject.ReportsMenu.LandButton_Click(Object sender, EventArgs e) in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\ReportsMenu.vb:line 4 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(ApplicationContext context) at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine) at AuctioneerProject.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: System.Data.OleDb.OleDbException ErrorCode=-2147217904 Message="No value given for one or more required parameters." Source="Microsoft Office Access Database Engine" StackTrace: at System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling(OleDbHResult hr) at System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) at System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior) at System.Data.OleDb.OleDbCommand.ExecuteReader() at AuctioneerProject.LandReport.load_Land() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 37 at AuctioneerProject.LandReport.PriceRadioButton_CheckedChanged(Object sender, EventArgs e) in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 79 at System.Windows.Forms.RadioButton.OnCheckedChanged(EventArgs e) at System.Windows.Forms.RadioButton.set_Checked(Boolean value) at AuctioneerProject.LandReport.InitializeComponent() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.designer.vb:line 40 at AuctioneerProject.LandReport..ctor() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 5 InnerException:

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  • Reading Binary file in C

    - by darkie15
    Hi All, I am having following issue with reading binary file in C. I have read the first 8 bytes of a binary file. Now I need to start reading from the 9th byte. Following is the code: fseek(inputFile, 2*sizeof(int), SEEK_SET); However, when I print the contents of the array where I store the retrieved values, it still shows me the first 8 bytes which is not what I need. Can anyone please help me out with this? Regards, darkie

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  • Problem with FlowLayout

    - by atch
    public class MyFrame extends JFrame { public MyFrame(String title) { setSize(200, 200); setTitle(Integer.toString(super.getSize().width)); setLayout(new FlowLayout()); for (int i = 0; i < 5; ++i) { JButton b = new JButton(); b.setSize(90,50); b.setText(Integer.toString(b.getSize().width)); this.add(b);![alt text][1] } this.setVisible(true); } } why if having button widht 90 I'm getting window where three buttons are in one row instead of two?

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  • Java: Using Comman line arguments to process the names of files

    - by Kat
    I'm a writing a program that will determine the number of lines, characters, and average word length for a text file. For the program, the specifications say that the file or files will be entered as a command line argument and that we should make a TestStatistic object for each file entered. I don't understand how to write the code for making the TestStatistic objects if the user enters more than one file.

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  • Linux bash: when to use egrep instead of grep?

    - by Michael Mao
    Hi all : I am preparing for a Linux terminal assessment now, I tried to Google and found most resources are referring to the basic "grep" rather than the more powerful "egrep" -- well, that is at least what the professor said in lecture. I am always working with small samples so performance tuning is a thing too far away. So basically I'd like to know are there any areas where I must switch to egrep to do it in a better way? Is it safe to work with basic "grep" as for now? will there be potential risks? Sorry about my limited knowledge on Linux shell commands, the man page looks like a maze to me and honestly I haven't put much time in understanding all the features both command provide.

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  • Recursive languages vs context-sensitive languages

    - by teehoo
    In Chomsky's hierarchy, the set of recursive languages is not defined. I know that recursive languages are a subset of recursively enumerable languages and that all recursive languages are decidable. What I'm curious about is how recursive languages compare to context-sensitive languages. Can I assume that context-sensitive languages are a strict subset of recursive languages, and therefore all context-sensitive languages are decidable?

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