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Posted : Friday, 08 July 2011, 13:42 | Permalink | Mark Here

jedimastersterling

Simple question and you are going to think i'm stupid for asking but i'm just getting my feet wet.

You know how in old dos programs the computer asks for a yes or no response by saying something like kdsajfs jhskhafds? y/n. I tried to implement that in a C++ program like so

char response;
cout <<"askjdune kksed? y/n\n";
cin>> response;
if (response == y)
else if (response == n)
else

the problem is the computer wants to treat y and n as variables. So how do you make if comparisons for characters responses?

Posted : Friday, 08 July 2011, 13:49 | Permalink | Mark Here

shroom_monk

WW Entries : 8

Anything you want read as a string needs to be in double quotes. Without them, y and n are treated as variables. So your above code should be: char response; cout <<"askjdune kksed? y/n\n"; cin>> response; if (response == "y") else if (response == "n") else --> See the quotes on lines 4 and 5? That should do it. ----- A mushroom a day keeps the doctor away... Keep It Simple, Shroom!

Posted : Friday, 08 July 2011, 14:51 | Permalink | Mark Here

jedimastersterling

ok, i tried it now it says that i can't make comparisons between pointers and integers

Posted : Friday, 08 July 2011, 14:54 | Permalink | Mark Here

shroom_monk

WW Entries : 8

Hmm... what does your entire code look like now? Exactly as the above? ----- A mushroom a day keeps the doctor away... Keep It Simple, Shroom!

Posted : Friday, 08 July 2011, 15:10 | Permalink | Mark Here

HoboBen

WW Entries : 9

(This is true for C, I assume this is true for C++)

As it's just a char, you'll want to use single quotes.

"a" with double quotes is a string literal (like "abcdef").

'a' with single quotes is a character (so 'abcdef' would be invalid).

The compiler is complaining because "y" with double quotes is of type "const char *", whereas 'y' with single quotes is of type "char" (which can be compared to your char response variable).

This is why the compiler printed an error about making comparisons between pointers and integers. The response variable of type char is a type of integer, and "y" is a pointer to a string constant. Therefore, you were making a comparison between a pointer and an integer (which is not what you wanted in this case).

Easy fix:

char response;
cout <<"askjdune kksed? y/n\n";
cin>> response;
if (response == 'y')
{
/* Do Yes */
}
else if (response == 'n')
{
/* Do No */
}
else
{
/* Neither yes nor no. Print an error message or something. */
}

-->

If you use a char array for a full string, you use the strcmp function (look up strcmp for more information)

char *response;

cout <<"askjdune kksed? y/n\n";
cin>> response;

if (strcmp(response, "yes") == 0)
{
/* Yes */
}
else if (strcmp(response, "no") == 0)
{
/* no */
}
else
{
/* Error! */
}

-->

-----

github

Posted : Friday, 08 July 2011, 15:13 | Permalink | Mark Here

shroom_monk

WW Entries : 8

Ah, I hadn't thought of that. Silly me. I use std::string for most of my string ops anyway, so I forget the subtleties of char. /excusemaking ----- A mushroom a day keeps the doctor away... Keep It Simple, Shroom!

Posted : Friday, 08 July 2011, 15:16 | Permalink | Mark Here

Jayenkai

WW Entries : 103

To clarify, because for a long time I used to go "Well, why the hell is a single letter different!?!?"..

"a" = The word "a"
whereas
'a' = the number 97, which is the ascii code for the letter a.

You're better off with using strcmp, like HoboBen says, because it's much less confusing that way. (well, kinda!)

Don't expect C to do nice string things like every other language on the planet. It won't!

-----

Posted : Friday, 08 July 2011, 19:12 | Permalink | Mark Here

jedimastersterling

HoboBen's sugestion worked perfectly. Thanks man.