uppercase/lowercase swap function

[Pavel]

My task was to write a program that reads keyboard input to EOF and that echoes the input except for digits, converting each uppercase character to lowercase, and vice versa.

#include <iostream.h>
#include <ctype.h>
int main(void)
{char ch;
while ((ch=cin.get())!='$')
{ if (islower(ch)) toupper(ch);
else if (isupper(ch)) tolower(ch);
if (isalpha(ch) || isspace(ch) || ispunct(ch))
cout <<ch;}
cin.get();
cin.get();
return 0;
}

Please help me out to work out why toupper( ) and tolower( ) functions are not executed?

[r035198x]

My task was to write a program that reads keyboard input to EOF and that echoes the input except for digits, converting each uppercase character to lowercase, and vice versa.

#include <iostream.h>
#include <ctype.h>
int main(void)
{char ch;
while ((ch=cin.get())!='$')
{ if (islower(ch)) toupper(ch);
else if (isupper(ch)) tolower(ch);
if (isalpha(ch) || isspace(ch) || ispunct(ch))
cout <<ch;}
cin.get();
cin.get();
return 0;
}

Please help me out to work out why toupper( ) and tolower( ) functions are not executed?

I'm curious to know what you got as output there. It seems you cout only if (isalpha(ch) || isspace(ch) || ispunct(ch))

you should indent your code probably and make good use of { }

And also use code tags when posting code.

[DeMan]

I'm not entirely familiar with those functions, but I would imagine that toupper RETURNS a char (and same for tolower) so yoiu should have

#include <iostream.h>
#include <ctype.h>
 
int main(void)
{
  char ch;
  while ((ch=cin.get())!='$')
  { 
    if (islower(ch)) 
      ch = toupper(ch);
    else if (isupper(ch)) 
      ch = tolower(ch);
    if (isalpha(ch) || isspace(ch) || ispunct(ch)) 
      cout <<ch;
  }
  cin.get();
  cin.get();
  return 0;
}
 

[DeMan]

and with

isalpha(ch)
 

alphabetic characters are output.......?

[r035198x]

I'm not entirely familiar with those functions, but I would imagine that toupper RETURNS a char (and same for tolower) so yoiu should have

#include <iostream.h>
#include <ctype.h>
 
int main(void)
{
char ch;
while ((ch=cin.get())!='$')
{ 
if (islower(ch)) 
ch = toupper(ch);
else if (isupper(ch)) 
ch = tolower(ch);
if (isalpha(ch) || isspace(ch) || ispunct(ch)) 
cout <<ch;
}
cin.get();
cin.get();
return 0;
}
 

You are right. This is probably what the OP intended

[Ganon11]

Also, you won't have to check for spaces or punctuation. You should just be able to output each character after you switch from uppercase to lowercase. The toupper() and tolower() functions actually return an integer variable (the ASCII number representing that char), so you will have to cast the result of these functions to a character (static_cast<char>(toupper(ch));).

Also, the toupper() and tolower() functions only return something different if the character given is lowercase or uppercase, respectively. If you pass it a space, or a backslash, for example, the function will return the ASCII value of a space or backslash, since neither of these count as a letter and, therefore, cannot be uppercase or lowercase.

[Pavel]

I'm not entirely familiar with those functions, but I would imagine that toupper RETURNS a char (and same for tolower) so yoiu should have

#include <iostream.h>
#include <ctype.h>
 
int main(void)
{
  char ch;
  while ((ch=cin.get())!='$')
  { 
    if (islower(ch)) 
      ch = toupper(ch);
    else if (isupper(ch)) 
      ch = tolower(ch);
    if (isalpha(ch) || isspace(ch) || ispunct(ch)) 
      cout <<ch;
  }
  cin.get();
  cin.get();
  return 0;
}
 

Thank you very much it works quite well, I forget a simple assignment