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how can I write a double pointer like FILE **
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Hi,
ahmedo047 wrote: how can I write a double pointer like FILE **
You can't directly. But why would you need it? The only thing that comes close is passing a
reference type (such as a File) to a method, in that case you can use the out or ref keywords
turning the parameter basically into a double indirection. Is that what you intend? If not,
please be more specific.
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I am trying to convert (c#) the following c+++ code.I can be able to use the out or ref keywords for single pointer but I dont know how I can write double pointer
#include<stdio.h>
#include<math.h>
#define ZERO 1.0E-20
#define true 1
#define false 0
main()
{
double A,FA,B,FB,C,P,FP,TOL;
int I,NO,OK,FLAG;
FILE *OUP[1];
double absval(double);
double F(double);
void INPUT(int *, double *, double *, double *, double *, double *, int *);
void OUTPUT(FILE **, int *);
INPUT(&OK, &A, &B, &FA, &FB, &TOL, &NO);
if (OK) {
OUTPUT(OUP, &FLAG);
/* STEP 1 */
I = 1;
/* STEP 2 */
OK = true;
while ((I<=NO) && OK) {
/* STEP 3 */
/* compute P(I) */
C = (B - A) / 2.0;
P = A + C;
/* STEP 4 */
FP = F(P);
if (FLAG == 2) fprintf(*OUP,"%3d %15.8e %15.7e \n",I,P,FP);
if ((absval(FP)<zero)> /* procedure completed successfully */
fprintf(*OUP,"\nApproximate solution P = %11.8f \n",P);
fprintf(*OUP,"with F(P) = %12.8f\n",FP);
fprintf(*OUP,"Number of iterations = %3d",I);
fprintf(*OUP," Tolerance = %15.8e\n",TOL);
OK = false;
}
else {
/* STEP 5 */
I++;
/* STEP 6 */
/* compute A(I) and B(I) */
if ((FA*FP) > 0.0) {
A = P; FA = FP;
}
else {
B = P; FB = FP;
}
}
}
if (OK) {
/* STEP 7 */
/* procedure completed unsuccessfully */
fprintf(*OUP,"\nIteration number %3d",NO);
fprintf(*OUP," gave approximation %12.8f\n",P);
fprintf(*OUP,"F(P) = %12.8f not within tolerance : %15.8e\n",FP,TOL);
}
fclose(*OUP);
}
return 0;
}
/* Change function F for a new problem */
double F(double X)
{
double f;
f = ( X + 4.0 ) * X * X - 10.0;
return f;
}
void INPUT(int *OK, double *A, double *B, double *FA, double *FB, double *TOL, int *NO)
{
double X;
char AA;
printf("This is the Bisection Method.\n");
printf("Has the function F been created in the program immediately preceding\n");
printf("the INPUT function?\n");
printf("Enter Y or N\n");
scanf("%c",&AA);
if ((AA == 'Y') || (AA == 'y')) {
*OK = false;
while (!(*OK)) {
printf("Input endpoints A < B separated by blank\n");
scanf("%lf %lf", A, B);
if (*A > *B) {
X = *A; *A = *B; *B = X;
}
if (*A == *B) printf("A cannot equal B\n");
else {
*FA = F(*A);
*FB = F(*B);
if (*FA*(*FB) > 0.0) printf("F(A) and F(B) have same sign\n");
else *OK = true;
}
}
*OK = false;
while(!(*OK)) {
printf("Input tolerance\n");
scanf("%lf", TOL);
if (*TOL <= 0.0) printf("Tolerance must be positive\n");
else *OK = true;
}
*OK = false;
while (!(*OK)) {
printf("Input maximum number of iterations - no decimal point\n");
scanf("%d", NO);
if (*NO <= 0) printf("Must be positive integer\n");
else *OK = true;
}
}
else {
printf("The program will end so that the function F can be created\n");
*OK = false;
}
}
void OUTPUT(FILE **OUP, int *FLAG)
{
char NAME[30];
printf("Select output destination\n");
printf("1. Screen\n");
printf("2. Text file\n");
printf("Enter 1 or 2\n");
scanf("%d", FLAG);
if (*FLAG == 2) {
printf("Input the file name in the form - drive:name.ext\n");
printf("A:OUTPUT.DTA\n");
scanf("%s", NAME);
*OUP = fopen(NAME, "w");
}
else *OUP = stdout;
fprintf(*OUP,"Bisection Method\n");
printf("Select amount of output\n");
printf("1. Answer only\n");
printf("2. All intermeditate approximations\n");
printf("Enter 1 or 2\n");
scanf("%d", FLAG);
if (*FLAG == 2) fprintf(*OUP, " I P F(P)\n");
}
/* Absolute Value Function */
double absval(double val)
{
if (val >= 0) return val;
else return -val;
}
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You don't need a double pointer. Both an array and a Stream are reference types, so if you pass a Stream array to a method you get the same effect as a double pointer. You don't even have to pass the array by reference.
However, as there is only ever one file pointer in the array, the array is pointless in the first place.
Despite everything, the person most likely to be fooling you next is yourself.
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Hi,
your code would translate to C# without a single pointer; almost all arguments to INPUT and OUTPUT
need the out keyowrd, no pointer stuff required. And the FILE stuff is handled
completely differently in .NET
May I suggest you look at some existing C# programs, and/or study a book on the language.
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hi
i create a userControl that has a property named 'Caption' that works like TextBox.Text, in paint event, i wrote this code to display Caption property :
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.DrawString(this.Caption, new Font("tahoma", 8), Brushes.Black, 0, 4);
}
it works good, but at designTime, when i add it to my form and set it's Caption, unlike textBox,it does not refresh automatic to display new Text, in paint event, also i use Invalidate(),Invalidate(false),Refresh() methods but it hasn't correct result.
how to solve my problem ?
thanks
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Hi,
I would need to see more code to actually be able to help you out.
I must insist though that you shouldn't create (and not dispose of!) a new font for every paint action.
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thanks for reply
no matter which font is used, the problem is that how to refresh my control to display new caption value after i set it in designTime.
here is my ful source Code :
public partial class UserControl1 : UserControl
{
private string _caption;
public string Caption
{
get { return _caption; }
set { _caption = value; }
}
public UserControl1()
{
InitializeComponent();
this.Height = 20;
this.Width = 100;
this.BackColor = Color.White;
}
protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.DrawString(this.Caption, new Font("tahoma", 8), Brushes.Black, 0, 4);
base.OnPaint(e);
}
}
thanks
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Hi,
your Caption setter only modifies a string, it does not affect the GUI at all.
You need to include an Invalidate(); right there, and I would
swap the two lines in OnPaint to make sure the string is painted last.
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thanks a lot Luc
i was modify Caption properties as follow :
public string Caption
{
get { return _caption; }
set
{
_caption = value;
this.Invalidate();
}
}
it was work good and my problem was solved.
thanks again.
regards
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I'm trying to search the source code of the web page, but the string I declare doesn't hold enough characters. This is my code.
String webSource = String.Empty;
webSource = webBrowser1.DocumentText;
Form2 form2 = new Form2(webSource);
form2.Show();
When I check this in Internet Explorer, the source of my program is less than half of what it shows as in IE.
What's the problem and how can I fix it?
Thanks in advance.
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I also want to add that I am trying to obtain the first image returned from a google image search. Right now, I am using the html of the search page to obtain the link to the first image. An alternative method would also be appreciated.
Thanks.
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Im making a small app in which i can write telephone notes and other stuff at work. Im using a tab control to add different types of tabs and everything is working as intended. The thing is, id like to be able to save all the tabs and their contents when i close the app (or whenever i choose) so that i can i.e. restart the computer and such without loosing any notes. If anyone can point me in the right direction that would be great. Thanks!
I haven't lost 'till I'm the last one to cross the finishline.
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You can either serialize the data or write it to file yourself using streams.
Giorgi Dalakishvili
#region signature
my articles
#endregion
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ive been looking into serializing and it looks like i can do that. Besides, its as good an excuse as any to learn serializing The thing is, i dont have any concrete variables to serialize. Is there som way to "grab" all the controls and contents of the controls in the tab control or the entire form and then serialize that?
I haven't lost 'till I'm the last one to cross the finishline.
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You can create custom class to store data from the tab control. Then just serialize it.
Giorgi Dalakishvili
#region signature
my articles
#endregion
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I think I understand what your getting at, and then again not... I haven't coded for long and i don't realy know where to start with that so... Any helpful links tips or links? Anything would be nice.
I haven't lost 'till I'm the last one to cross the finishline.
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Man that is one advanced program! For my standards atleast But it helped me alot actually. I think i get what you are doing when you save the file paths and serialize them to be used later. The thing is, i dont know how to do that with my tabs. When i choose to save the tabs i dont know how to get the tabs and the contents of the tabs. Is there some way to get all the tabs in the tab control, and the contents of the tabs (text in text boxes and such)?
I haven't lost 'till I'm the last one to cross the finishline.
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TabPageCollection returns all the tabs in tab control. In order to get contents of the tab, you can build your own class to hold data and use databinding so that it will be automatically populated by the values of the controls on the tabpage.
Giorgi Dalakishvili
#region signature
my articles
#endregion
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hi,
I want to write a program or a service which disconnect a dial up connection whenever for example the mouse doesn't move for 5 minutes or ...
please help me on this.
please tell in what library's i can find useful things.
thanks
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I know that there is a possibility to get the name of the file after choosing it in the FileDialog, like this:
String str=fileDialog1.fileName()
The String(str) includes the full address of the file.
for example:
str="c:\windows\system\abc.txt"
but i want only the file name(abc.txt).
how can i receive only the file name and not the full address?
thank you
G.
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use safefilename like this
DialogResult dr= openFileDialog1.ShowDialog();
if(dr==DialogResult.OK)
MessageBox.Show(openFileDialog1.SafeFileName);
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Try Path.GetFileName[^] passing the full path you get from the file dialog. Also see other static methods in the Path[^] class in case you are interested.
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