Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Siquo]

Yes. Please explain. Me no understando.

Throwing balls at eachother is a common american pastime, and apparently expected of fathers to do with their sons. As it builds character. However, that is usually already a primitive type. Jokes sound really stupid when you have to explain them.

[MagmaMcFry]

Yes. Please explain. Me no understando.

Throwing balls at eachother is a common american pastime, and apparently expected of fathers to do with their sons.

I see what you did there.

[Siquo]

... oh no I did not.

Damnit.

[MagmaMcFry]

... oh no I did not.

Damnit.

Oh. Wait, no, that's not what I meant at all D:

[Soadreqm]

Yes. Please explain. Me no understando.

The main code, starting at "public static void main(String[] args){" creates two new instances of the object P, called "parent" and "child". Object P is defined to have an attribute "target", which is another object P. The child's target is set to be the parent, and the parent's target is set to be the child. The parent's "aim" function is called, with a new Ball object as the parameter. The Ball has no attributes or functions, but extends the Throwable class, making Balls the same type of thing as Java Exceptions.

The P.aim(Ball B) function has a try-catch block, where the only thing done inside the try part is to throw a Ball, specifically the Ball that P.aim took as a parameter. Since a Throwable was thrown, the catch block is triggered, and calls the aim function of the P that is the current P's target.

So, you get the parent and child recursively tossing balls around ad infinitum.

It's basically a really convoluted pun.

[Dutchling]

Thanks.

That's absolutely hilarious.

[Putnam]

Speaking of XKCD and programming, this got a good laugh out of me.

[Sirus]

C again

This time we read from a source file, count the number of letters, numbers, other characters, total them all, and print the counts. We've been told to use ctype.h (despite not being used in this chapter AT ALL) to determine which category each character falls in to.

Problem is when I try to run the program, I get insanely high counts that cannot be accurate (also the data isn't transferring between functions properly, but one step at a time). Take a look-see and point out my error(s)?

Spoiler (click to show/hide)

Code: [Select]

/*
This program reads the number of letters, numbers, and other characters in a file
Written by: Sirus
Date: 3/21/2013
*/

#include <stdio.h>
#include <ctype.h>

//Function Declarations
int getText(FILE* spText, int* l, int* n, int* o, int* t);
void printText(int l, int n, int o, int t);

int main (void)
{
//Local Declarations
FILE* spText;

int letters = 0;
int numbers = 0;
int other = 0;
int total = 0;

//Statements
printf("Reading source file...\n");
if (!(spText = fopen("source.txt", "r")))
{
printf("ERROR: Could not open file!\n");
return 100;
}

getText(spText, &letters, &numbers, &other, &total);

printText(letters, numbers, other, total);

fclose(spText);

printf("End of program.\n");
}

int getText(FILE* spText, int* l, int* n, int* o, int* t)
{
//Local declarations
int ioResult;

//Statements
while ((ioResult = fgetc(spText)) != EOF)
{
if (isalpha(ioResult))
l++;
else if (isdigit(ioResult))
n++;
else
o++;

//Add to the total
t++;

}
        //These printfs are just to see if values are being counted properly
printf("Letters: %d\n", l);
printf("Numbers: %d\n", n);
printf("Other:   %d\n", o);
printf("Total:   %d\n", t);

return;
}

void printText(int l, int n, int o, int t)
{
//Statements
printf("Letters: %d\n", l);
printf("Numbers: %d\n", n);
printf("Other:   %d\n", o);
printf("Total:   %d\n", t);

return;
}

[RulerOfNothing]

When you say you get insanely high counts that cannot be accurate, can you show us a test file and the results you get from running the program on this file?

[Sirus]

Spoiler: Source file (click to show/hide)

The quick brown fox jumps over the fence!!
0090 90 90 90 ##%%
The rain in Spain stays in the plain??

Spoiler: Output (click to show/hide)

[RulerOfNothing]

It's pretty obvious now. Incrementing a pointer-to-int does something different to incrementing an int, and you were incrementing the pointers and not the variables that they were pointing to. I think you can do something like *l++ to do this (or maybe (*l)++).

[Putnam]

Isn't & the dereference operator?

[Sirus]

It's pretty obvious now. Incrementing a pointer-to-int does something different to incrementing an int, and you were incrementing the pointers and not the variables that they were pointing to. I think you can do something like *l++ to do this (or maybe (*l)++).

That did it! It was actually this
(*l)++;
What's better, the numbers are now passing correctly to the print function. Thanks a lot!

Isn't & the dereference operator?

I did try that at first, but it didn't help

[alexandertnt]

Isn't & the dereference operator?

& gets the memory address of a variable. It is also used to pass things by reference (which is generally easier than using pointers). For example:

Code: [Select]

int i = 5;
int *j = &i; // Pointer to i

[/code]
void DoSomething(int &i){
  i = 5;
}
int main(){

}

[alexandertnt]

Isn't & the dereference operator?

* is the dereference operator (-> also works for calling member functions on struct/class pointers). & gets the memory address of a variable (sort of the opposite of the dereference operator). It is also used to pass things by reference (which is generally easier than using pointers). For example:

Code: [Select]

int main(){
  int i = 5;
  int *q = &i; // Pointer to i
  cout << (*q) << endl; // prints 5;
}


Code: [Select]

void DoSomething(int &i){
  i = 5;
}
int main(){
  int variable = 12;
  DoSomething(variable);
  cout << variable << endl; //outputs 5
  return 0;
}

it can also be used to create variables that function similarly to pointers with reduced errors. (you dont have to dereference them or worry about segaults, but you cant perform pointer arithmetic on them):

Code: [Select]

int main(){
  int var = 55;
  int &morevar = var;
  morevar = 10;
  cout << var << endl // prints 10
}