Alphabet to Integer conversion program== Segmentation Fault.

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Alphabet to Integer conversion program== Segmentation Fault.

 
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  #1
May 1st, 2009
I am getting a segmentation fault when i run the follwing program.
This program takes in a const char* and returns the integer format.

I also need advice on converting a C++ Octal or Hexadecimal Notationed string to an integer.

Here is the code

C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cstring>
  3.  
  4. int atoi(const char*);
  5. int single_char_convert(char);
  6. int pow(int,int); 
  7. int main()
  8. {
  9. std::cout<<atoi("123");
  10. }
  11.  
  12. int atoi(const char *str)
  13. {
  14. 	int length=std::strlen(str)-1;
  15. 	int result=0;
  16. 	for(int x=0;x<=length;x++)
  17. 	{
  18. 		int y=length-x;
  19. 		char character=str[x];
  20. 		int converted_char=single_char_convert(character);
  21. 		result+=(converted_char*pow(10,y));			
  22. 	}
  23. 	return result;
  24. }
  25.  
  26. int single_char_convert(char a)
  27. {
  28. 	switch(a)
  29. 	{
  30. 		case '0':
  31. 			return 0;
  32. 		case '1':
  33. 			return 1;
  34. 		case '2':
  35. 			return 2;
  36. 		case '3':
  37. 			return 3;
  38. 		case '4':
  39. 			return 4;
  40. 		case '5':
  41. 			return 5;
  42. 		case '6':
  43. 			return 6;
  44. 		case '7':
  45. 			return 7;
  46. 		case '8':
  47. 			return 8;
  48. 		case '9':
  49. 			return 9;
  50. 	}
  51. }
  52.  
  53. int pow(int number,int powerof)
  54. {
  55. 	if(powerof==1)
  56. 	{
  57. 	return number;
  58. 	}
  59. 	else
  60. 	{
  61. 	return number*pow(number,--powerof);
  62. 	}
  63. }



Code tags work sometimes and code tags donot work.
Last edited by Sky Diploma; May 1st, 2009 at 1:13 pm. Reason: Code tag isnt taking a copy paste maybe
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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  #2
May 1st, 2009
>I also need advice on converting a C++ Octal or Hexadecimal Notationed string to an integer.

To do conversions between numbers and strings stringstreams are often used

Lines 28-50 can be replaced by: return a-'0';
Last edited by tux4life; May 1st, 2009 at 1:26 pm.
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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  #3
May 1st, 2009
>I am getting a segmentation fault when i run the follwing program.
How does your code handle N^0?

>Code tags work sometimes and code tags donot work.
Define "do not work".
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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  #4
May 1st, 2009
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Originally Posted by tux4life View Post
>I also need advice on converting a C++ Octal or Hexadecimal Notationed string to an integer.

To do conversions stringstreams are often used
Well True,
I pretty much dont know whether I can use stringstreams to solve this exercise.

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Originally Posted by The C++ Programming Language Edition 3 by Bjarne Stroustrup has this Assignment in 6.6.16

Write a function atoi(const char*) that takes a string containing digits and returns the corresponding ints. for example
atoi("123")
returns 123

Modify atoi () to handle C++ octal and hexadecimal notations in addition to decimal numbers and also character constant notations
Will a-'0';
be true for all the constants.in different character map sets?


Narue thanks for the reply

Here is the new code

C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cstring>
  3.  
  4. int atoi(const char*);
  5. int single_char_convert(char);
  6. int pow(int,int); 
  7. int main()
  8. {
  9. std::cout<<atoi("123");
  10. }
  11.  
  12. int atoi(const char *str)
  13. {
  14. 	int length=std::strlen(str)-1;
  15. 	int result=0;
  16. 	for(int x=0;x<=length;x++)
  17. 	{
  18. 		int y=length-x;
  19. 		char character=str[x];
  20. 		int converted_char=single_char_convert(character);
  21. 		result+=(converted_char*pow(10,y));			
  22. 	}
  23. 	return result;
  24. }
  25.  
  26. int single_char_convert(char a)
  27. {
  28. 	switch(a)
  29. 	{
  30. 		case '0':
  31. 			return 0;
  32. 		case '1':
  33. 			return 1;
  34. 		case '2':
  35. 			return 2;
  36. 		case '3':
  37. 			return 3;
  38. 		case '4':
  39. 			return 4;
  40. 		case '5':
  41. 			return 5;
  42. 		case '6':
  43. 			return 6;
  44. 		case '7':
  45. 			return 7;
  46. 		case '8':
  47. 			return 8;
  48. 		case '9':
  49. 			return 9;
  50. 	}
  51. }
  52.  
  53. int pow(int number,int powerof)
  54. {
  55. 	if (powerof==0)
  56. 	{
  57. 	return 1;
  58. 	}
  59. 	else
  60. 	{
  61. 	return number*pow(number,--powerof);
  62. 	}
  63. }
Last edited by Sky Diploma; May 1st, 2009 at 1:42 pm.
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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May 1st, 2009
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Originally Posted by Sky Diploma View Post
Well True,
I pretty much dont know whether I can use stringstreams to solve this exercise.
You can: if you convert the C++ string back to a C-string after the conversion, but that was probably not the intention of the assignment
Last edited by tux4life; May 1st, 2009 at 1:43 pm.
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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  #6
May 1st, 2009
>Will a-'0';
>be true for all the constants.in different character map sets?
Digits are required by the C++ standard to be contiguous, but if you need to convert to hexadecimal, you can't portably use that trick. Try an array instead, using the index as your value:
C++ Syntax (Toggle Plain Text) 
  1. const char digits[] = "0123456789ABCDEF";
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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May 1st, 2009
Narue, you're right but I provided him with this trick because his function was returning an integer value ...
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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May 1st, 2009
Hey can you explain me of converting a string of char containing a hex notation of a number to a int?
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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May 1st, 2009
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Originally Posted by Sky Diploma View Post
Hey can you explain me of converting a string of char containing a hex notation of a number to a int?
Take a look at this
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Re: Alphabet to Integer conversion program== Segmentation Fault.

 
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May 1st, 2009
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Originally Posted by tux4life View Post
Narue, you're right but I provided him with this trick because his function was returning an integer value ...
And that makes a difference, how?
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