How do I convert a string from lowercase to uppercase without using array notation?

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The task is to convert a string from lowercase to uppercase without using array notation?

The hint I was given was "modify the string pointer itself", I thought you couldn't modify a string pointer. I'm not sure how to work the while loop.

Any help would be great.

What I have tried:

int main(void)
{

  uppercase_no_array("reverse");

  return(0);
}

void uppercase_no_array(char* input)
{

  char* copy = malloc(sizeof(char) * strlen(input));
  strcpy(copy, input);

  printf("%s", copy);

  while(copy != '\0')
  {

   
  }
return;

}

Posted 12-Sep-17 1:59am

Member 13404013

Updated 12-Sep-17 2:38am

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Comments

Afzaal Ahmad Zeeshan 12-Sep-17 8:07am

You're almost there, just add the statement inside that while loop and check if the character falls in lower case ASCII, and change it to upper case ASCII.

2 solutions

Solution 2

Quote:
The hint I was given was "modify the string pointer itself"

From my point of view that means that you can modify the string in-place using a pointer:

C++

char *p;
p = input_string;
while (*p)
{
    /* char_to_upper() has to be implemented */
    *p = char_to_upper(*p);
    p++;
}

Posted 12-Sep-17 2:38am

Jochen Arndt

Comments

Klaus-Werner Konrad 13-Sep-17 11:22am

This would pretty sure lead to a Memory Access Violation; the Argument from main() is a string LITERAL ...

Jochen Arndt 13-Sep-17 11:40am

No. They are not literals but the argv[] entries point to an allocated buffer. It is common to modify command line arguments in place.

From the C standard (5.1.2.2.1 Program startup):
"177 — The parameters argc and argv and the strings pointed to by the argv array shall be modifiable by the program, and retain their last-stored values between program startup and program termination."

Klaus-Werner Konrad 25-Sep-17 10:07am

Huh ...

int main(void)
{
uppercase_no_array("reverse");
return(0);
}

is CLEARLY a literal, not an command line argument

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OriginalGriff · Accepted Answer · 2017-09-12T02:10:00

Solution 1

When you allocate the Memory, copy points at the first character in the space. You then use that to copy the input to an output area - you don't really need to do that at all, just use the two pointers you already have: copy and input

char* uppercase_no_array(char* input)
{
  char* mem = malloc(sizeof(char) * (strlen(input) + 1));
  char* copy = mem;
  char c;
  do
  {
  c = *input++;
  ... uppercase it here ...
  *copy++ = c;
  } while(c != '\0')
  return mem;
}

Posted 12-Sep-17 2:10am

OriginalGriff

Updated 12-Sep-17 2:27am

v2

Comments

Jochen Arndt 12-Sep-17 8:17am

You forgot to allocate space for the NULL byte.

OriginalGriff 12-Sep-17 8:26am

I was using his code, but yes, you are right.
Fixed.

OriginalGriff 12-Sep-17 8:27am

If this wasn't an early student exercise, I'd also worry about deallocation, but ...