C / C++ / MFC

Re: Passing parameters to constructor - very obvious and basic question from an OF

16-Sep-15 21:09

Could you please post sample code?

Richard MacCutchan16-Sep-15 21:31

Richard MacCutchan

16-Sep-15 21:31

It is normal practice to add parameters that remain constant in the object to the constructor like:

C++

class Foo
{
private:
    int paramThatDoesNotChangeOften;
public:
    Foo(int someParam)
    {
        paramThatDoesNotChangeOften = someParam);
    }
};

You could then add a getter method to return the value to the user if it's value is needed outside the class.

Is that what you are querying?

Re: Passing parameters to constructor - very obvious and basic question from an OF

Vaclav_19-Sep-15 1:29

Vaclav_

19-Sep-15 1:29

Thanks for replies.
It may be stupid, but that is what I am trying to avoid.
Now I would have "someParam" - actually global array and a class copy of the same so it can be accessed by class methods.
I am trying to save some memory of embedded processor.
Kinda of wishful thinking ahead.

I won't get to upset if I need to make a local copies.
Would using "this" pointer work making local copy?
I just tryied "standard" this.name = name but could not make it work on pointers.
I guess I am still struggling with using pointers.

Addendum
I have decided to KISS and I'll be making copies of the parameters using "this" pointer.
One question remains - since all of the parameaters passed are de facto constants - harwdware pins, LCD size etc. and won't be modified by the class, why can't I just use "this>LCD_x_size" as variable instead of "this->LCD_x_size = LCD_x_size" Now the class local varaible is "LCD_x_size".
And yes, I read somewhere that using same symbols for "name" and "variable" is OK.
Confusing, but OK.

-- modified 19-Sep-15 17:56pm.

Re: Passing parameters to constructor - very obvious and basic question from an OF

Daniel Pfeffer19-Sep-15 21:30

Daniel Pfeffer

19-Sep-15 21:30

If the parameters are actually constants, how about instantiating a template class?

C++

int const PROCESSOR_COUNT = 42;

template <int processor_count>
scheduler
{
   // constructors, other methods

private:
   processor_data data[processor_count];
};

scheduler<PROCESSOR_COUNT> sched;

If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.

--Winston Churchill

Real time drawing using multithreading

FrankStar8912-Sep-15 23:57

FrankStar89

12-Sep-15 23:57

Hello there,
I am looking for the best Way/Strategy to "Continuously read data from the HW in real-time and draw some GUI-diagram in Parallel". Performance would be a big matter here since the graph has to be drawn in real-time.

Its just coming to my mind about 1) creating 1 worker-thread for reading process, and 2) another for GUI drawing.
But I am looking for perfection and suggestions here.

1) Is there any specific Design-Pattern that would fit this?. If so, please suggest.
2) Whats the best way(container) to read data by the worker-thread and keep it for the GUI-thread to process. FIFO? or some other class?

Thanks in advance for your suggestion and advice.

jschell13-Sep-15 12:24

jschell

13-Sep-15 12:24

FrankStar89 wrote:
Performance would be a big matter here since the graph has to be drawn in real-time.

How many points per second?
Presumably there is no data munging at all?

FrankStar8914-Sep-15 21:48

FrankStar89

14-Sep-15 21:48

Thanks Jschell.
I am not sure yet how many points per sec. ( still in the initial stage.) I think there would be data munging for sure.
Anyway, what I was looking here mostly any "usual Design Pattern" for this kind of problem in general. (1 thread is reading and another is drawing simultaneously).
Thanks again.

jschell15-Sep-15 11:25

jschell

15-Sep-15 11:25

FrankStar89 wrote:
I am not sure yet how many points per sec.

That of course would be the first requirement before proceeding. It impacts everything.

David Crow14-Sep-15 4:12

David Crow

14-Sep-15 4:12

For worker threads, read here.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

Need help with this little C program

FrankStar8914-Sep-15 21:50

FrankStar89

14-Sep-15 21:50

Thanks David,
That would surely be helpful.

Member 1197963712-Sep-15 12:44

12-Sep-15 12:44

Hey guys,

I have to write a small program in C, I'll explain what it has to do.

You have product a, b and c

The input is the prices of a, b and c in cents.

You have to spend exactly 100 euros on the purchase of exactly 100 products.

As output I need to get a list of all possible combinations.

Lets give an example. Lets say the input is "88 99 102":
then the output has to be exactly like this:
1 a, 62 b, 37 c
4 a, 48 b, 48 c
7 a, 34 b, 59 c
10 a, 20 b, 70 c
13 a, 6 b, 81 c

I'm relatively new in progamming in C, so all help is appreciated, the deadline is short for this one.

Objective-C

int main(int argc, char *argv[]) {
  int a, b, c, x, y, z /* x=numbers of a y= numbers of b z= numbers of c*/
  printf("price of a:\n");
  printf("price of b:\n");
  printf("price of c:\n");
  scanf("%d, %d, %d" ,&a, &b, &c);
while (x+y+z=100){
x*a+y*b+z*c=10000

As you can see, I tried writing some code, but im stuck right here...

Richard MacCutchan12-Sep-15 21:00

Richard MacCutchan

12-Sep-15 21:00

This is not a programming problem, more one of mathematics. You first need to work out the algorithm to calculate the numbers of each product that you can buy for €100. Once you have that then turning it into code should be fairly trivial.

CPallini13-Sep-15 6:52

13-Sep-15 6:52

A brute force approach would work, e.g.

for ( x = 1; x <= 98; x++)
  for ( y = 1; y <= (99 - x); ++y)
  {
    z = 100 - x - y;
    // here check if the items sum to 100
  }

Member 1197963713-Sep-15 8:05

13-Sep-15 8:05

Thanks. I'm finally getting the hang of it. I'll try something tomorrow and I will let you peoples know if I succeed or not.

CPallini13-Sep-15 10:23

13-Sep-15 10:23

You are welcome.

Member 1197963713-Sep-15 12:24

13-Sep-15 12:24

Thanks again, I make improve in the code, but it ain't working as supposed.

I'm really wondering where the code is wrong, I get no output or a wrong output (e.g. 100 100 100 gives as output only 100 a, 0 b, 0 c.)

I tried different things and I guess I'm almost there, but can't fix it.

So please, help me with this code.

Objective-C

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char *argv[]) 
{
	int a, b, c, x, y, z; /* x=numbers of a y= numbers of b z= numbers of c*/
	printf("price of a:\n");
  	printf("price of b:\n");
  	printf("price of c:\n");
	scanf("%d, %d, %d" ,&a, &b, &c);

	for(x = 0; x <= 100; x++)
	{
  		for(y = 0; y <= (100 - x); ++y)
  		{
    		        z = 100 - x - y;
    		        if(x*a + y*b + z*c == 10000)
    		        {
        		      printf("%d a, %d b, %d c",x ,y ,z);
    		        }
  		}
	}

return 0;
}

CPallini13-Sep-15 21:13

13-Sep-15 21:13

You don't use correctly scanf. Try

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char *argv[])
{
  int a, b, c, x, y, z; /* x=numbers of a y= numbers of b z= numbers of c*/

  int done = 0;

  while ( done == 0)
  {
    printf("please enter the price of a:\n");
    if ( scanf("%d", &a) != 1) continue;
    printf("please enter the price of b:\n");
    if ( scanf("%d", &b) != 1) continue;
    printf("please enter the price of c:\n");
    if ( scanf("%d", &c) != 1) continue;
    done = 1;
  }

  for(x = 0; x <= 100; x++)
  {
      for(y = 0; y <= (100 - x); ++y)
      {
                z = 100 - x - y;
                if(x*a + y*b + z*c == 10000)
                {
                  printf("%d a, %d b, %d c\n",x ,y ,z);
                }
      }
  }

return 0;
}

C++

Member 1197963714-Sep-15 2:42

14-Sep-15 2:42

Thank you so much! It works great. I had to change the code a bit to pass all testcases, but finally I made it Smile | :)

.

However, I'd like to know how that piece of code between the While { ... } works, I don't really get it.

done = 0, so while ( done == 0) is true. Then it runs the code and you can enter the values. But why does it need the done == 0 and why the != 1? I understand the done = 1, otherwise it will run the while statement again, right?

Member 1197963714-Sep-15 2:55

14-Sep-15 2:55

Well, I don't know why it did not work the first time, but I tried to simplify the code and ended up with:

printf("price of a: price of b: price of c: ");
scanf("%d %d %d", &a, &b, &c);

instead of that thing with while { ... }

And this time, it did work. I do not really see the difference with the code I used before that did not work.. :p

CPallini14-Sep-15 3:40

14-Sep-15 3:40

Even the code you used before would have work with a suitable input, that is if the user would have entered, for instance

100,100,100

that is, with the commas.

However, the code handling input from the user should be more robust.

David Crow14-Sep-15 4:40

David Crow

14-Sep-15 4:40

Perhaps your problem can be broken up into two smaller problems: 1) Find all combinations of A+B+C that equal (quantity) 100. I *think* that gives you a set of about 4851 combinations. 2) For each of those, multiply A by 0.88, b by 0.99, and C by 1.02, and if that product equals 100 euros, you have a match.

Member 1197963714-Sep-15 6:10