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strtoul() function use

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strtoul() function use

 
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  #1
Nov 22nd, 2007
OK, I finally figured out command line arguments... my program is called prime, in the console i need to type "prime 7" and the program will tell me if its a prime or not.

heres my code:
C++ Syntax (Toggle Plain Text) 
  1. #include <cstdlib>
  2. #include <iostream>
  3. #include <iomanip>
  4. #include <stdlib.h>
  5.  
  6. using namespace std;
  7.  
  8.  
  9. int main(int argc, char *argv[])
  10. {
  11.    const unsigned long arraySize = 1000000;
  12.    bool a[arraySize];
  13.    unsigned long num1;
  14.    unsigned long num2;
  15.    unsigned long num3;
  16.    unsigned long counter = 0;
  17.    unsigned long primes = 0;
  18.    char z;
  19.    unsigned long answer = 0;
  20.  
  21. //Initializing elements to 1 
  22.  
  23. for (int i = 0; i < arraySize; i++)             
  24. {
  25.    a[i] = 1;
  26. }       
  27. // For array subscript 2, all elements beyond 2 in the array that
  28. // are multiples of 2 will be set to zero ; for array subscript 3, 
  29. // all elements beyond 3 in the array that 
  30. // are multiples of 3 will be set to zero
  31.  
  32.  
  33. for (int i = 2; i * i < arraySize; i++)
  34. {
  35.     if (a[i])
  36.        for (int j = i + i; j < arraySize; j += i)
  37.           a[j] = 0;
  38. } 
  39. // if user enters more than 3 numbers or 0 numbers
  40. // program should output useful information
  41. // and title and author
  42.  
  43. if ((argc > 4) || (argc == 1))
  44. {
  45.  cout<<"This is Programming Assignment #5"<<endl;
  46.  cout<<"THE SIEVE OF ERATOSTHENES"<<endl;
  47.  cout<<"by Jeremy Rice"<<endl;
  48.  cout<<endl;
  49.  cout<<"Usage:"<<endl;
  50.  cout<<"\tprime num1 - determines if num1 is a prime"<<endl;
  51.  cout<<"\tprime num1 num2 - displays primes between numbers."<<endl;
  52. }
  53.  
  54. // if user enters one number
  55. // program should determine if that number is a prime
  56.  
  57. if (argc == 2)
  58. {  
  59.    if (a[argc] == 1)
  60.    {   
  61.        num1 = strtoul(argv[]);
  62.        counter++;
  63.        cout<<"This is a prime number."<<endl;  
  64.    }
  65.    else
  66.    cout<<"This is not a prime number."<<endl;
  67. }
  68.  
  69.  
  70.  
  71. // if user enters 2 numbers
  72. // program, should calculate the prime numbers 
  73. // between the two numbers
  74.  
  75. if (argc == 3)
  76.    {
  77.  
  78.    }
  79.  
  80.  
  81.  
  82. return EXIT_SUCCESS;
  83. }


heres the part I need help with
C++ Syntax (Toggle Plain Text) 
  1. // if user enters one number
  2. // program should determine if that number is a prime
  3.  
  4. if (argc == 2)
  5. {  
  6.    if (a[argc] == 1)
  7.    {   
  8.        num1 = strtoul(argv[]);
  9.        counter++;
  10.        cout<<"This is a prime number."<<endl;  
  11.    }
  12.    else
  13.    cout<<"This is not a prime number."<<endl;
  14. }

what do I put in the num1 = strtoul(argv[]) to take the number entered in the command line prompt?
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Re: strtoul() function use

 
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  #2
Nov 22nd, 2007
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I finally figured out command line arguments
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what do I put in the num1 = strtoul(argv[]) to take the number entered in the command line prompt?
A contradiction!
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Re: strtoul() function use

 
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  #3
Nov 22nd, 2007
If you enter prime 7 as the command-line argument then the word prime will be in argv[1] and '7' is in argv[2], making argc == 3, not 2. argv[0] is almost always the name of the executable program.
Last edited by Ancient Dragon; Nov 22nd, 2007 at 12:53 pm.
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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Re: strtoul() function use

 
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  #4
Nov 22nd, 2007
I don't know about the stroul function.

I also have no idea what you are planning to do with this.
C++ Syntax (Toggle Plain Text) 
  1. if (argc == 3)
  2.    {
  3.  
  4.    }

Let me try. arg[0] refers to the name of exe, which is tprime over here. Then onwards, arg[r] refers to the rth command line argument.
"You know you're a computer geek when you try to shoo a fly away from the monitor screen with your cursor. That just happened to me. It was scary." - Juuso Heimonen.

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Re: strtoul() function use

 
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  #5
Nov 22nd, 2007
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what do I put in the num1 = strtoul(argv[]) to take the number entered in the command line prompt?
You will have to convert these strings containing numbers to integers by an appropriate function.
"You know you're a computer geek when you try to shoo a fly away from the monitor screen with your cursor. That just happened to me. It was scary." - Juuso Heimonen.

"The only truly secure computer is one buried in concrete, with the power turned off and the network cable cut." - Anonymous.
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Re: strtoul() function use

 
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  #6
Nov 22nd, 2007
Oops! Ancient Dragon & I replied just at about the same time!!
"You know you're a computer geek when you try to shoo a fly away from the monitor screen with your cursor. That just happened to me. It was scary." - Juuso Heimonen.

"The only truly secure computer is one buried in concrete, with the power turned off and the network cable cut." - Anonymous.
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Re: strtoul() function use

 
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  #7
Nov 22nd, 2007
Ok, so this is what i have... sorry for the ignorance, but i am slowly getting it..

if i typed "prime 45 70"
the program rightly displays primes between 45 and 70..
if I type "prime" the program rightly displays who it was created by and how to use it...except with a "memory fault"at end.

If I type " prime 6" I just get "memory fault" it should display if that number is prime or not..

What am i doing wrong to get that memory fault.. That is the last thing I need to do with this program, again sorry, but thank you for patience and your help.


C++ Syntax (Toggle Plain Text) 
  1. #include <cstdlib>
  2. #include <iostream>
  3. #include <iomanip>
  4. #include <stdlib.h>
  5.  
  6. using namespace std;
  7. const unsigned W = 10;
  8.  
  9. int main(int argc, char *argv[])
  10. {
  11.    const unsigned long arraySize = 1000000;
  12.    bool a[arraySize];
  13.    unsigned long num1;
  14.    unsigned long num2;
  15.    unsigned long num3;
  16.    unsigned long counter = 0;
  17.    unsigned long primes = 0;
  18.    char z;
  19.    unsigned long answer = 0;
  20.  
  21. //Initializing elements to 1 
  22.  
  23. for (int i = 0; i < arraySize; i++)             
  24. {
  25.    a[i] = 1;
  26. }       
  27. // For array subscript 2, all elements beyond 2 in the array that
  28. // are multiples of 2 will be set to zero; for array subscript 3, 
  29. // all elements beyond 3 in the array that 
  30. // are multiples of 3 will be set to zero
  31.  
  32.  
  33. for (int i = 2; i * i < arraySize; i++)
  34. {
  35.     if (a[i])
  36.        for (int j = i + i; j < arraySize; j += i)
  37.           a[j] = 0;
  38. } 
  39. // if user enters more than 3 numbers or 0 numbers
  40. // program should output useful information
  41. // and title and author
  42.  
  43. if ((argc > 4) || (argc == 1))
  44. {
  45. cout<<"This is Programming Assignment #5"<<endl;
  46. cout<<"THE SIEVE OF ERATOSTHENES"<<endl;
  47. cout<<"by Jeremy Rice"<<endl;
  48. cout<<endl;
  49. cout<<"Usage:"<<endl;
  50. cout<<"\tprime num1 - determines if num1 is a prime"<<endl;
  51. cout<<"\tprime num1 num2 - displays primes between numbers."<<endl;
  52. }
  53.  
  54.  
  55.  
  56. num1 = atoi(argv[1]);
  57. num2 = atoi(argv[2]);
  58. num3 = num1;
  59. // if user enters one number
  60. // program should determine if that number is a prime
  61.  
  62. if ((argc > 1) && (argc < 3))
  63. {
  64.    if (a[num1] == 1)
  65.    cout<<num1<<" is a prime number."<<endl;
  66.    else
  67.    cout<<num1<<" is not a prime number."<<endl;
  68. }
  69.  
  70. // if user enters 2 numbers
  71. // program, should calculate the prime numbers 
  72. // between the two numbers
  73.  
  74. if (argc == 3) 
  75.    for (int i = num1; num1 < num2; num1++)
  76.  
  77.     if (num1 < num2)
  78.     if (a[num1] == 1)
  79.      {
  80.       counter++; 
  81.       cout<<setw(W)<<num1;
  82.      }
  83.        else if
  84.         (a[num1] == 0)
  85.      {
  86.          cout<<"";
  87.      }   
  88.         else 
  89.           cout<<"num1 must be lower than num2."<<endl;          
  90. if (num1 > num2)
  91. {
  92. cout<<"Error: Invalid user specified number."<<endl;
  93. return 0;
  94. }
  95. cout<<endl;
  96. cout<<"There are "<<counter<<" primes between "<<num3<<" and "<<num1<<endl;
  97. return EXIT_SUCCESS;
  98. }
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Re: strtoul() function use

 
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  #8
Nov 22nd, 2007
Between lines 51 and 52 you need to add return EXIT_SUCCESS;. (If you start your code blocks with the name of the language you are using, you get line numbers: [code=C++].)

Line 56: are you sure there is an argv[ 1 ]?
Line 57: are you sure there is an argv[ 2 ]?
Line 62: isn't that the same as if (argc == 2) ?
Line 90: you could just swap the numbers so that num1 < num2...

A few other notes. Choose C or C++, not both:
1. Use #include <cstdlib>
2. When dealing with boolean values, use the keywords true and false, so it is obvious that you are dealing with a boolean value and not an integer.
3. Likewise, when testing boolean values, say
if (a[num1])
or
if (a[num1] == true)
4. Stick lines 43..52 as the first thing in your main. (There are good reason's why, but I don't want to take the time to explain them all now...)
5. Use functions.
6. Old C people and those who don't know better like to have their students use const int foosize = 12000; and junk like that. That's really about the same thing as saying: #define foosize 12000
The better way is just to declare your array as bool a[1000000]; and use the sizeof operator to get its size later:
for (int i = 0; i < sizeof( a )/sizeof( a[ 0 ] ); i++)
Well, it is another way, at least. (It prevents you from being tempted to do dumb things.)
7. You forgot to use strtoul()...

You seem to have a pretty good grasp of what your code should be doing. Good job.

Hope this helps.
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