help me understand this function

[momotaro]

the function is quite simple but there is one line of it that i did not get the point of its use it the one in bold please help!

char GetCommand()
{
    char command;
    printf(
        "\n\t\t\t[I]nsert entry\n\n"
        "\t\t\t[P]rint list\n\n"
        "\t\t\t[S]ize of teh list\n\n"
        "\t\t\t[D]elete list\n\n"
        "\t\t\t[C]lear list\n\n"
        "\t\t\t[T]raverse the list\n\n"
        "Select your command and press <Enter> : "
        );
    while(TRUE){
        while((command = getchar()) == '\n')
            ;
        command = tolower(command);
    if(command == 'i' || command == 'p' ||
       command == 's' || command == 'd' ||
       command == 'c' || command == 't'){
           while(getchar() != '\n')
               ;            
                                         return command
    }
    printf("Please enter a valid command");
    }
}

[AdrianH]

char GetCommand()
{
    char command;
    printf(
        "\n\t\t\t[I]nsert entry\n\n"
        "\t\t\t[P]rint list\n\n"
        "\t\t\t[S]ize of teh list\n\n"
        "\t\t\t[D]elete list\n\n"
        "\t\t\t[C]lear list\n\n"
        "\t\t\t[T]raverse the list\n\n"
        "Select your command and press <Enter> : "
        );
    while(TRUE){
        while((command = getchar()) == '\n')
            ;
        command = tolower(command);
    if(command == 'i' || command == 'p' ||
       command == 's' || command == 'd' ||
       command == 'c' || command == 't'){
           while(getchar() != '\n')
               ;            
                                         return command
    }
    printf("Please enter a valid command");
    }
}

The semicolon after the while() indicates an empty body. It would be equivialant to putting empty braces ('{}')

BTW, I'd use comments next time. bolding doesn't show up well.


Adrian

[momotaro]

thank you, i know that but my question was about the usefulness of that line of code since it add no thing to teh correctness!!!
i omited it but my function still works fine!!
please illuminate me

[AdrianH]

thank you, i know that but my question was about the usefulness of that line of code since it add no thing to teh correctness!!!
i omited it but my function still works fine!!
please illuminate me

Try typing in 'is a grand day' as your command with and without the while loop you highlighted. It should become clear.


Adrian

[weaknessforcats]

This code:

while((command = getchar()) == '\n')
            ;
 

is the same as:

while((command = getchar()) == '\n')
{
 
}
 

That is, you stay in the while loop until you stop pressing the enter key and enter a real command.

[momotaro]

printf("thank you!");

p.s: trial :)

[Savage]

printf("thank you!");

p.s: trial :)

Original!!

Savage