looking for a function

I am supposed to use a 'library function' to check if a letter is a vowel. My guess is that the function is in the cctype header - but I don't know the function - or if one even exists. Could someone point me to this function, and an example of it's use please?

int isalpha( int ch );

That's what I know of; you have to manually check for vowels.

Why did you ask this when writing your own "isvowel" is a 5 minute job (if that)?

I figured I would have to - but the exercise tells me to do this:

Code:

 "Design a program that asks the usr to input a letter. Use a library 
function to determine and output whether or not the letter is a
 vowel..."

I know isalpha checks for a letter - but the directions in the exercise do seem a tad confusing - so what I'll do, is check for a letter with isalpha() and then write some code to check for a vowel with an if statement.

Originally Posted by ahluka

Why did you ask this when writing your own "isvowel" is a 5 minute job (if that)?

I'm just trying to do what the book is asking... I haven't hit the chapter on functions yet.

If a lecturer or equivalent gave that to you as an assignment ask them what the hell the std lib function is because I'd really like to know

EDIT: Sorry didn't see above post (same time ).

Writing such a function is not as easy as it may first seems: vowels and consonants are not written with the same letters in all writing systems, and sometimes whether a letter is a vowel or consonant depends on the context.

Take for example the letter Y. In English sometimes it's a vowel (lady), sometimes a consonant (year), and sometimes a diphtong (my). In other languagues it's always a consonant (Spanish), and in yet others always a vowel (Finnish).

Well, I'm having trouble compiling - something is wrong with a static cast that tried to put together... also - could you guys help me double check my program's logic? I'm not sure the program is going to act like it is supposed to. So here's the order of operation that I want: Get user input, check for a letter, tell if said letter is uppercase or lowercase, check for a vowel, and then output the letter as lowercase at the end.

Using a ton of if statements always seems to confuse me!
EDIT: along with confusing me - I can never get clean formatting when I use them.

Here's the code - with errors after:

Code:

#include <cstdlib>
#include <iostream>
#include <cctype>

using std::cout;
using std::cin;
using std::endl;

int main()
{
    char letter;
    
    cout <<"Please enter a letter on your keyboard: ";
    cin >> letter;
    cout << endl;
    
    if(std::isalpha(letter)) {
            if(std::isupper(letter)) {
                                            cout <<" Letter is uppercase\n";
                                            }
                        if(std::islower(letter)) {
                                            cout <<" Letter is lowercase.\n";
                                            }            
          
          
          static_cast<char>(std::toupper(letter)) <<endl;
          if(letter == 'A' || 'E' || 'I' || 'O' || 'U' || 'Y') {
                    cout <<"Your letter is a vowel.\n";
                    }
                    
          else{
               cout <<"Your letter is not a vowel.\n";
               }
          
          static_cast<char>(std::tolower(letter)); <<endl;
          cout <<"The letter was: " << letter;
                         
                         }                                               
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

Errors are as follows:

Code:

 
 C:\Dev-Cpp\letters.cpp In function `int main()': 
26 C:\Dev-Cpp\letters.cpp invalid operands of types `char' and `<unknown type>' to binary `operator<<' 
35 C:\Dev-Cpp\letters.cpp expected primary-expression before '<<' token 
 C:\Dev-Cpp\Makefile.win [Build Error]  [letters.o] Error 1

static_cast<char>(std::toupper(letter)) <<endl;
static_cast<char>(std::tolower(letter)); <<endl;
Spot the ;
You also probably meant
cout << static_cast<char>(std::toupper(letter)) <<endl;

> if(letter == 'A' || 'E' || 'I' || 'O' || 'U' || 'Y')
This is not what you want (it's always true)
Try
if(letter == 'A' || letter == 'E' || letter == 'I' || letter == 'O' || letter == 'U' || letter == 'Y')

Originally Posted by Salem

static_cast<char>(std::toupper(letter)) <<endl;
static_cast<char>(std::tolower(letter)); <<endl;
Spot the ;
You also probably meant
cout << static_cast<char>(std::toupper(letter)) <<endl;

> if(letter == 'A' || 'E' || 'I' || 'O' || 'U' || 'Y')
This is not what you want (it's always true)
Try
if(letter == 'A' || letter == 'E' || letter == 'I' || letter == 'O' || letter == 'U' || letter == 'Y')

Hey I apprechiate the fixes! thank you! What I want to do though, is actually change the value of the letter to it's uppcase equivalent - that's what I wanted to do with the static cast to type char - but I guess I misunderstood how that worked with toupper()/tolower()....

Could you show me how to change, say letter a to A and then store it? Because in my program, before it checks if the letter is a vowel - it skips the static cast and goes straight into the conditional if statement. when it should change the letter to uppercase and then go through the condtional statement.

How about use an assignment statement?

Originally Posted by Salem

How about use an assignment statement?

I'm not sure what you mean by that...

Originally Posted by mabufo

I'm not sure what you mean by that...

= ...

Originally Posted by ahluka

= ...

Well yes of course that - but how do I combine that with my static cast?

Oh well,
letter = static_cast<char>(std::toupper(letter));