Programming Forums > Application Development > C

lectricpharaoh · Dec 4th, 2006, 6:03 PM

Another linkie here might help. In fact, you can go through this site to see how to use a whole variety of functions.

That said, you might find it easier using C++ constructs and functions rather than C ones. Something like

(Toggle Plain Text)

std::cout << "Your score is " << score << " out of a possible " << total << " points.\n";

might be easier to work with than

(Toggle Plain Text)

printf("Your score is %d out of a possible %d points.\n", score, total);

This is especially true when you have a lot of variables. With printf(), they are identified in the output not with their names, but with placeholders that must correspond to additional parameters you pass (this is why printf() can fail so badly if you don't pass in the correct number and/or type of arguments, and it's also why the compiler can't error-check the additional arguments).

Arevos · Dec 4th, 2006, 6:28 PM

Quote:

Originally Posted by lectricpharaoh

That said, you might find it easier using C++ constructs and functions rather than C ones.

That wouldn't be C, though :p

m0rb1d · Dec 5th, 2006, 10:27 AM

Learning C is turning out to be much more difficult than I originally had anticipated. Everything was going excellent, I was understanding the content, and could make my own code based on what I was learning. THEN, the page on arrays comes by.

(Toggle Plain Text)

http://computer.howstuffworks.com/c10.htm

It's a little difficult to explain, but it's like, the comprehension is sitting right on the tip of my brain, and is refusing to make it's way to the understanding part of the brain. Very frustrating. I see the code, understand what it's supposed to do, and can BEGIN to see the HOW of it all, and THEN ZIP - I'm suddenly struck with stupidity.

Sorry for the off topicness, but, needed to rant somewhere.

DaWei · Dec 5th, 2006, 11:06 AM

You haven't said what you don't understand, so let me just generalize. An array is a collection of contiguous memory locations that all hold the same type of value (ints, for example, or chars, or whatever). The array has a name. The name represents the address of the first location. The first location also has an index value of 0. Each succeeding element has an index. These increment from the beginning. You address these elements by combining the name of the array with an index value. MyArray [4] would be the fifth element in the array (since the first element is 0). Since MyArray (without an index attached) represents the first element, you could also access it by treating MyArray as a pointer and adding 4. If that's too confusing at the moment, stick to the index access method.

If this doesn't help, post specifically what is confusing to you.

m0rb1d · Dec 5th, 2006, 11:41 AM

Well, to be more specific, I suppose assigning values to each number in the array. For instance:

You have myArray[5]. I understand that I can declare each one seperately, such as

(Toggle Plain Text)

myArray[0] = 10
myArray[1] = 34

etc, but, doing it with a loop.... I dont quite understand. Goes back to that, tip of the brain comment I made earlier. It seems to me that the following should work:

(Toggle Plain Text)

main()
{ 
      int n;
      n = 0;
      int myArray[n];
      WHILE ( myArray[n] < 5 )
             myArray[n] = n
             n = n + 1
}

Reading the code, it appears to me that the WHILE loop will set myArray[n] to the value of n. It then sets n to n + 1, which, after the first loop, would be 1. So, the 2nd time through, it will make myArray[n] equal to 1, third time through it will be 2, and so on.

Now, I am aware this will not work. It should be:

(Toggle Plain Text)

WHILE ( n < 5 )

What I dont understand, is why the previous will not work. It seems like it's doing the same thing, only instead of setting the first array value ( myArray[0] ) to whatever, it setting the array variable n to whatever, which then sets myArray[0] to whatever n was. Seems like a lot of extra, un-needed work.

Narue · Dec 5th, 2006, 11:52 AM

>Learning C is turning out to be much more difficult than I originally had anticipated.
People have some strange expectations, so let me drive the point home: Programming is hard.

>It seems to me that the following should work:
It should this way:

(Toggle Plain Text)

int main ( void )
{ 
  int n;
  int myArray[5];

  n = 0;

  while ( n < 5 ) {
    myArray[n] = n;
    n = n + 1;
  }

  return 0;
}

>What I dont understand, is why the previous will not work.
That's more subtle. When you declare the array, it's filled with garbage values by default. The only way to clear those values is to overwrite them. Now, when n is 0, you're still accessing myArray[0], but there's nothing there that you can predict. The problem is the order of operations. You use the contents of myArray[n] to control the loop, but you haven't assigned a value to myArray[n] yet.

You can do what you want, but you have to be very careful about the order of operations. You need to assign to myArray[n] first, then test myArray[n], then increment n:

(Toggle Plain Text)

int main ( void )
{ 
  int n;
  int myArray[5];

  n = 0;

  /* Infinite loop to keep the syntax simple */
  while ( 1 ) {
    myArray[n] = n;

    if ( myArray[n] >= 5 )
      break;

    n = n + 1;
  }

  return 0;
}

You can shorten that with other C features, but I'm not sure you've encountered them yet:

(Toggle Plain Text)

n = 0;

do {
  myArray[n] = n;
} while ( myArray[n++] < 5 );

Harakim · Dec 5th, 2006, 8:00 PM

Also, notice that he used {} (braces). By default, a loop, switch/case statement, or if/else statement will only execute the next line of code. If you want to execute more lines of code, you will have to enclose it in braces.

lectricpharaoh · Dec 5th, 2006, 10:46 PM

Quote:

Originally Posted by Arevos

That wouldn't be C, though :p

My bad. I didn't notice the forum. In my defense, though, the OP mentioned he was using DevC++, and that he was finding C difficult; I don't feel a recommendation to start with an easier-to-grasp approach is entirely unwarranted. :/

Quote:

Originally Posted by Harakim

Also, notice that he used {} (braces).

What is it with everyone assuming Narue is a guy?

Harakim · Dec 5th, 2006, 11:14 PM

Sorry.

bl00dninja · Dec 6th, 2006, 1:27 AM

just some formatting crap. the data is the same with or w/o the "4".

it makes it print pretty. forget about it. some esoteric stdio nonsense with printf().

forget the "switch to python or ruby!!!" crap too. you made a good decision based on good advice. just keep doing what you're doing.

Dec 4th, 2006, 6:03 PM	#11
lectricpharaoh Caffeinated Neural Net Join Date: Jun 2005 Location: Dry west coast of Canada Posts: 1,007 Rep Power: 5	Another linkie here might help. In fact, you can go through this site to see how to use a whole variety of functions. That said, you might find it easier using C++ constructs and functions rather than C ones. Something like (Toggle Plain Text) std::cout << "Your score is " << score << " out of a possible " << total << " points.\n"; std::cout << "Your score is " << score << " out of a possible " << total << " points.\n"; might be easier to work with than (Toggle Plain Text) printf("Your score is %d out of a possible %d points.\n", score, total); printf("Your score is %d out of a possible %d points.\n", score, total); This is especially true when you have a lot of variables. With printf(), they are identified in the output not with their names, but with placeholders that must correspond to additional parameters you pass (this is why printf() can fail so badly if you don't pass in the correct number and/or type of arguments, and it's also why the compiler can't error-check the additional arguments). __________________ And once again, Probability proves itself willing to sneak into a back alley and service Drama as would a copper-piece harlot. - Vaarsuvius, Order of the Stick

Dec 5th, 2006, 10:27 AM	#13
m0rb1d Newbie Join Date: Nov 2006 Posts: 19 Rep Power: 0	Learning C is turning out to be much more difficult than I originally had anticipated. Everything was going excellent, I was understanding the content, and could make my own code based on what I was learning. THEN, the page on arrays comes by. (Toggle Plain Text) http://computer.howstuffworks.com/c10.htm http://computer.howstuffworks.com/c10.htm It's a little difficult to explain, but it's like, the comprehension is sitting right on the tip of my brain, and is refusing to make it's way to the understanding part of the brain. Very frustrating. I see the code, understand what it's supposed to do, and can BEGIN to see the HOW of it all, and THEN ZIP - I'm suddenly struck with stupidity. Sorry for the off topicness, but, needed to rant somewhere.

Dec 5th, 2006, 11:06 AM	#14
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	You haven't said what you don't understand, so let me just generalize. An array is a collection of contiguous memory locations that all hold the same type of value (ints, for example, or chars, or whatever). The array has a name. The name represents the address of the first location. The first location also has an index value of 0. Each succeeding element has an index. These increment from the beginning. You address these elements by combining the name of the array with an index value. MyArray [4] would be the fifth element in the array (since the first element is 0). Since MyArray (without an index attached) represents the first element, you could also access it by treating MyArray as a pointer and adding 4. If that's too confusing at the moment, stick to the index access method. If this doesn't help, post specifically what is confusing to you. __________________ 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

Dec 5th, 2006, 11:41 AM	#15
m0rb1d Newbie Join Date: Nov 2006 Posts: 19 Rep Power: 0	Well, to be more specific, I suppose assigning values to each number in the array. For instance: You have myArray[5]. I understand that I can declare each one seperately, such as (Toggle Plain Text) myArray[0] = 10 myArray[1] = 34 myArray[0] = 10 myArray[1] = 34 etc, but, doing it with a loop.... I dont quite understand. Goes back to that, tip of the brain comment I made earlier. It seems to me that the following should work: (Toggle Plain Text) main() { int n; n = 0; int myArray[n]; WHILE ( myArray[n] < 5 ) myArray[n] = n n = n + 1 } main() { int n; n = 0; int myArray[n]; WHILE ( myArray[n] < 5 ) myArray[n] = n n = n + 1 } Reading the code, it appears to me that the WHILE loop will set myArray[n] to the value of n. It then sets n to n + 1, which, after the first loop, would be 1. So, the 2nd time through, it will make myArray[n] equal to 1, third time through it will be 2, and so on. Now, I am aware this will not work. It should be: (Toggle Plain Text) WHILE ( n < 5 ) WHILE ( n < 5 ) What I dont understand, is why the previous will not work. It seems like it's doing the same thing, only instead of setting the first array value ( myArray[0] ) to whatever, it setting the array variable n to whatever, which then sets myArray[0] to whatever n was. Seems like a lot of extra, un-needed work.

Dec 5th, 2006, 11:52 AM	#16
Narue Professional Programmer Join Date: Sep 2005 Posts: 419 Rep Power: 3	>Learning C is turning out to be much more difficult than I originally had anticipated. People have some strange expectations, so let me drive the point home: Programming is hard. >It seems to me that the following should work: It should this way: (Toggle Plain Text) int main ( void ) { int n; int myArray[5]; n = 0; while ( n < 5 ) { myArray[n] = n; n = n + 1; } return 0; } int main ( void ) { int n; int myArray[5]; n = 0; while ( n < 5 ) { myArray[n] = n; n = n + 1; } return 0; } >What I dont understand, is why the previous will not work. That's more subtle. When you declare the array, it's filled with garbage values by default. The only way to clear those values is to overwrite them. Now, when n is 0, you're still accessing myArray[0], but there's nothing there that you can predict. The problem is the order of operations. You use the contents of myArray[n] to control the loop, but you haven't assigned a value to myArray[n] yet. You can do what you want, but you have to be very careful about the order of operations. You need to assign to myArray[n] first, then test myArray[n], then increment n: (Toggle Plain Text) int main ( void ) { int n; int myArray[5]; n = 0; /* Infinite loop to keep the syntax simple / while ( 1 ) { myArray[n] = n; if ( myArray[n] >= 5 ) break; n = n + 1; } return 0; } int main ( void ) { int n; int myArray[5]; n = 0; / Infinite loop to keep the syntax simple */ while ( 1 ) { myArray[n] = n; if ( myArray[n] >= 5 ) break; n = n + 1; } return 0; } You can shorten that with other C features, but I'm not sure you've encountered them yet: (Toggle Plain Text) n = 0; do { myArray[n] = n; } while ( myArray[n++] < 5 ); n = 0; do { myArray[n] = n; } while ( myArray[n++] < 5 ); __________________ Even if the voices aren't real, they have some pretty good ideas.

Dec 5th, 2006, 8:00 PM	#17
Harakim Hobbyist Programmer Join Date: May 2006 Location: West Jordan, Utah, United States Posts: 176 Rep Power: 3	Also, notice that he used {} (braces). By default, a loop, switch/case statement, or if/else statement will only execute the next line of code. If you want to execute more lines of code, you will have to enclose it in braces.

Dec 5th, 2006, 11:14 PM	#19
Harakim Hobbyist Programmer Join Date: May 2006 Location: West Jordan, Utah, United States Posts: 176 Rep Power: 3	Sorry.

Dec 6th, 2006, 1:27 AM	#20
bl00dninja Programming Guru Join Date: Oct 2004 Location: namespace std Posts: 1,246 Rep Power: 5	just some formatting crap. the data is the same with or w/o the "4". it makes it print pretty. forget about it. some esoteric stdio nonsense with printf(). forget the "switch to python or ruby!!!" crap too. you made a good decision based on good advice. just keep doing what you're doing. __________________ i put on my robe and wizard hat... Have you ever heard of Plato, Aristotle, Socrates?...Morons.

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Programming Forums > Application Development > C

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