Programming Forums > Application Development > C

jch02140 · Jul 28th, 2005, 5:33 AM

Hi, I am writting these codes on the practice paper and I am not sure if I am correct:

1.) Write a C function stats that receives three integers and returns the average of these three integers as a double value and the sum as an integer through the parameter sum. You only need to write the function. The function prototype is given below:

double stats(int x, int y, int z, int *sum);

Here is my code...

(Toggle Plain Text)

double stats(int x, int y, int z, int *sum)
{

double average = (double) (x + y + z) /3;
sum = x + y + z;
*sum = sum;

printf("Average is: 6.2f. \nSum is: %d.", average, *sum);
return (0);
}

2.) Write a C function min_max that receives three integers and return the minimum and maximum values. The function prototype is given below:

void min_max(int x, int y, int z, int *max, int *min);

Here is my code...

(Toggle Plain Text)

void min_max(int x, int y, int z, int *max, int *min)
{

if((x>y) && (y>z))
          max = x; min = z; *max=max; *min=min;
elseif((x>y) && (y<z))
          max = x; min = y; *max=max; *min=min;
elseif((y>x) && (x>z))
          max = y; min = z; *max=max; *min=min;
elseif((y>x) && (x<z))
          max = y; min = x; *max=max; *min=min;
elseif((z>x) && (x>y))
          max = z; min = y; *max=max; *min=min;
elseif((z>x) && (x<y))
          max = z; min = x; *max=max; *min=min;
printf("Maximum is %d.\nMinimum is %d.", *max, *min);
return (0);
}

Berto · Jul 28th, 2005, 6:20 AM

The first one is pretty much there you just need 1 ammendment i think

(Toggle Plain Text)

double stats(int x, int y, int z, int *sum)
{

double average = (double) (x + y + z) /3;
sum = x + y + z;
*sum = sum;

printf("Average is: 6.2f. \nSum is: %d.", average, *sum);
return (average); //so it returns the average va;lue and sum points to the sum
}

And the second one i changed a lot of it :/

(Toggle Plain Text)

void min_max(int x, int y, int z, int *max, int *min)
{

if((x>y) && (y>z)){
          *max = x; *min = z;
}else if((x>y) && (y<z)){
          *max = x; *min = y; 
}else if((y>x) && (x>z)){
          *max = y; *min = z; 
}else if((y>x) && (x<z)){
          *max = y; *min = x; 
}else if((z>x) && (x>y)){
          *max = z; *min = y; 
}else if((z>x) && (x<y)){
          *max = z; *min = x; 
}
printf("Maximum is %d.\nMinimum is %d.", *max, *min);

}

If you need to no why the second one was changed just ask

DaWei · Jul 28th, 2005, 7:40 AM

In the first one, you don't declare a local variable named sum (which would conflict with the integer pointer, "sum", anyway), so the code

(Toggle Plain Text)

sum = x + y + z;
*sum = sum;

will attempt to overwrite the pointer value with x + y + z (the compiler should throw an error with this line), then use the value of the sum as a pointer, which, if you actually got this far, would likely cause a seg fault. You're also not returning the value as instructed.

Try this:

(Toggle Plain Text)

double stats (int x, int y, int z, int *sum)
{
   int localSum = x + y + z;
   double average = (double) localSum / 3.0;
   *sum = localSum;

   printf ("Average is: 6.2f. \nSum is: %d.", average, *sum);
   return average;
}

As for the second, I would write it so that the process is clear to the reader:

Get the largest of two values: largest = x > y? x : y;
Get the largest of that and the third value: largest = largest > z? largest : z;

If you haven't encountered the ternary operator yet, just replace with the appropriate conditional construct you're familiar with.

Larry Wall, the author of Perl, says, "tmtowtdir". That's, "There's more than one way to do it right." In deciding among correct solutions, clarity makes a good criterion.

jch02140 · Jul 28th, 2005, 7:53 AM

I see. so a star in front of the variables is pass by pointers...
It is for deference purpose right?

DaWei · Jul 28th, 2005, 8:07 AM

That is correct. If you're unfamiliar with pointers, you might read the material at the link in my signature, Pointer Basics.

jch02140 · Jul 28th, 2005, 10:12 AM

Hi, just trying to see if I get it this time...

(Toggle Plain Text)

void min_max(int x, int y, int z, int *max, int *min)
{
int larger = x > y? x : y;
*max = larger > z? larger : z;

int smaller = x < y? x :y;
*min = smaller < z? smaller : z;
return;
}

I realised that this version produced some redundant check on the variables twice...

Also, can I do it this way?...

(Toggle Plain Text)

void min_max(int x, int y, int z, int *max, int *min) {
  if((*max = (x > y ? x : y)) < z) *max = z;
  if((*min = (x < y ? x : y)) > z) *min = z;
}

DaWei · Jul 28th, 2005, 10:33 AM

Actually, you can do it this way:

*max = z > (*max = x > y? x : y)? z : *max;

My comment regarding clarity versus terseness (which often doesn't result in reduced code) will come back to you the first time you go back to a program you wrote a year or so ago, in order to add to it. You won't know what the hell you did and will be tempted to call its author a dumbazz. Been there.

pr0gm3r · Jul 28th, 2005, 11:34 AM

Quote:

Originally Posted by DaWei

Actually, you can do it this way:

*max = z > (*max = x > y? x : y)? z : *max;

My comment regarding clarity versus terseness (which often doesn't result in reduced code) will come back to you the first time you go back to a program you wrote a year or so ago, in order to add to it. You won't know what the hell you did and will be tempted to call its author a dumbazz. Been there.

so am I, I took C++ class last spring 2004 and all the project that I did, I couldn't even remember what is the code for. I need to go over my program line by line...

I think in my opinion, we should use conditions statement such as if/else or switch, because it is much clear to read our program this way. Isn't it right?

^__^

DaWei · Jul 28th, 2005, 11:49 AM

If one is familiar with the ternary operator, it is VERY clear. Nesting/chained expression evaluation makes it very less so. Additionally, if one wants to do that, one needs to review the precedence of operations of the language and what things are evaluated left-to-right or right-to-left. Obfuscation can set in very quickly. On the other hand, if one uses a lot of individual if-else-else if constructs, the operation can be splattered over so much territory that it quickly becomes unclear that one is dealing with three values in a particularly relative way.

Jul 28th, 2005, 5:33 AM	#1
jch02140 Newbie Join Date: Jul 2005 Posts: 15 Rep Power: 0	I am new to C and I need some help in these two C questions Hi, I am writting these codes on the practice paper and I am not sure if I am correct: 1.) Write a C function stats that receives three integers and returns the average of these three integers as a double value and the sum as an integer through the parameter sum. You only need to write the function. The function prototype is given below: *double stats(int x, int y, int z, int sum);** Here is my code... (Toggle Plain Text) double stats(int x, int y, int z, int sum) { double average = (double) (x + y + z) /3; sum = x + y + z; sum = sum; printf("Average is: 6.2f. \nSum is: %d.", average, sum); return (0); } double stats(int x, int y, int z, int sum) { double average = (double) (x + y + z) /3; sum = x + y + z; sum = sum; printf("Average is: 6.2f. \nSum is: %d.", average, sum); return (0); } 2.) Write a C function min_max that receives three integers and return the minimum and maximum values. The function prototype is given below: *void min_max(int x, int y, int z, int max, int min);* Here is my code... (Toggle Plain Text) void min_max(int x, int y, int z, int max, int min) { if((x>y) && (y>z)) max = x; min = z; max=max; min=min; elseif((x>y) && (y<z)) max = x; min = y; max=max; min=min; elseif((y>x) && (x>z)) max = y; min = z; max=max; min=min; elseif((y>x) && (x<z)) max = y; min = x; max=max; min=min; elseif((z>x) && (x>y)) max = z; min = y; max=max; min=min; elseif((z>x) && (x<y)) max = z; min = x; max=max; min=min; printf("Maximum is %d.\nMinimum is %d.", max, min); return (0); } void min_max(int x, int y, int z, int max, int min) { if((x>y) && (y>z)) max = x; min = z; max=max; min=min; elseif((x>y) && (y<z)) max = x; min = y; max=max; min=min; elseif((y>x) && (x>z)) max = y; min = z; max=max; min=min; elseif((y>x) && (x<z)) max = y; min = x; max=max; min=min; elseif((z>x) && (x>y)) max = z; min = y; max=max; min=min; elseif((z>x) && (x<y)) max = z; min = x; max=max; min=min; printf("Maximum is %d.\nMinimum is %d.", max, min); return (0); }

Jul 28th, 2005, 6:20 AM	#2
Berto Programming Guru Join Date: Aug 2004 Posts: 1,022 Rep Power: 6	The first one is pretty much there you just need 1 ammendment i think (Toggle Plain Text) double stats(int x, int y, int z, int sum) { double average = (double) (x + y + z) /3; sum = x + y + z; sum = sum; printf("Average is: 6.2f. \nSum is: %d.", average, sum); return (average); //so it returns the average va;lue and sum points to the sum } double stats(int x, int y, int z, int sum) { double average = (double) (x + y + z) /3; sum = x + y + z; sum = sum; printf("Average is: 6.2f. \nSum is: %d.", average, sum); return (average); //so it returns the average va;lue and sum points to the sum } And the second one i changed a lot of it :/ (Toggle Plain Text) void min_max(int x, int y, int z, int max, int min) { if((x>y) && (y>z)){ max = x; min = z; }else if((x>y) && (y<z)){ max = x; min = y; }else if((y>x) && (x>z)){ max = y; min = z; }else if((y>x) && (x<z)){ max = y; min = x; }else if((z>x) && (x>y)){ max = z; min = y; }else if((z>x) && (x<y)){ max = z; min = x; } printf("Maximum is %d.\nMinimum is %d.", max, min); } void min_max(int x, int y, int z, int max, int min) { if((x>y) && (y>z)){ max = x; min = z; }else if((x>y) && (y<z)){ max = x; min = y; }else if((y>x) && (x>z)){ max = y; min = z; }else if((y>x) && (x<z)){ max = y; min = x; }else if((z>x) && (x>y)){ max = z; min = y; }else if((z>x) && (x<y)){ max = z; min = x; } printf("Maximum is %d.\nMinimum is %d.", max, min); } If you need to no why the second one was changed just ask __________________ "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. THAT'S relativity." - Albert Einstein

Jul 28th, 2005, 7:40 AM	#3
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	In the first one, you don't declare a local variable named sum (which would conflict with the integer pointer, "sum", anyway), so the code (Toggle Plain Text) sum = x + y + z; sum = sum; sum = x + y + z; sum = sum; will attempt to overwrite the pointer value with x + y + z (the compiler should throw an error with this line), then use the value of the sum as a pointer, which, if you actually got this far, would likely cause a seg fault. You're also not returning the value as instructed. Try this: (Toggle Plain Text) double stats (int x, int y, int z, int sum) { int localSum = x + y + z; double average = (double) localSum / 3.0; sum = localSum; printf ("Average is: 6.2f. \nSum is: %d.", average, sum); return average; } double stats (int x, int y, int z, int sum) { int localSum = x + y + z; double average = (double) localSum / 3.0; sum = localSum; printf ("Average is: 6.2f. \nSum is: %d.", average, sum); return average; } As for the second, I would write it so that the process is clear to the reader: Get the largest of two values: largest = x > y? x : y; Get the largest of that and the third value: largest = largest > z? largest : z; If you haven't encountered the ternary operator yet, just replace with the appropriate conditional construct you're familiar with. Larry Wall, the author of Perl, says, "tmtowtdir". That's, "There's more than one way to do it right." In deciding among correct solutions, clarity makes a good criterion. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 28th, 2005, 8:07 AM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	That is correct. If you're unfamiliar with pointers, you might read the material at the link in my signature, Pointer Basics. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 28th, 2005, 10:12 AM	#6
jch02140 Newbie Join Date: Jul 2005 Posts: 15 Rep Power: 0	Hi, just trying to see if I get it this time... (Toggle Plain Text) void min_max(int x, int y, int z, int max, int min) { int larger = x > y? x : y; max = larger > z? larger : z; int smaller = x < y? x :y; min = smaller < z? smaller : z; return; } void min_max(int x, int y, int z, int max, int min) { int larger = x > y? x : y; max = larger > z? larger : z; int smaller = x < y? x :y; min = smaller < z? smaller : z; return; } I realised that this version produced some redundant check on the variables twice... Also, can I do it this way?... (Toggle Plain Text) void min_max(int x, int y, int z, int max, int min) { if((max = (x > y ? x : y)) < z) max = z; if((min = (x < y ? x : y)) > z) min = z; } void min_max(int x, int y, int z, int max, int min) { if((max = (x > y ? x : y)) < z) max = z; if((min = (x < y ? x : y)) > z) min = z; }

Jul 28th, 2005, 7:53 AM	#4
jch02140 Newbie Join Date: Jul 2005 Posts: 15 Rep Power: 0	I see. so a star in front of the variables is pass by pointers... It is for deference purpose right?

Jul 28th, 2005, 10:33 AM	#7
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Actually, you can do it this way: max = z > (max = x > y? x : y)? z : max; My comment regarding clarity versus terseness (which often doesn't result in reduced code) will come back to you the first time you go back to a program you wrote a year or so ago, in order to add to it. You won't know what the hell you did and will be tempted to call its author a dumbazz. Been there. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers*

Jul 28th, 2005, 11:49 AM	#9
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	If one is familiar with the ternary operator, it is VERY clear. Nesting/chained expression evaluation makes it very less so. Additionally, if one wants to do that, one needs to review the precedence of operations of the language and what things are evaluated left-to-right or right-to-left. Obfuscation can set in very quickly. On the other hand, if one uses a lot of individual if-else-else if constructs, the operation can be splattered over so much territory that it quickly becomes unclear that one is dealing with three values in a particularly relative way. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > C

I am new to C and I need some help in these two C questions