Why doesn't this program detect that there is a whitespace?

Question

So I was working on this program again, and I encountered another problem. I am testing if a character is a space. However, instead of detecting that the there is a space, it stops the loop and doesn't do anything more. Here is my code:

string reet(char reet) {
if (isspace(reet) == true) {
    return "IA";
}
else {
    switch (reet) {
    case 'a':
        return "Zg";
        break;
    case'b':
        return "dA";
        break;
    case 'c':
        return "dG";
        break;
    case 'd':
        return "aw";
        break;
    case 'e':
        return "bw";
        break;
    case 'f':
        return "dQ";
        break;
    case 'g':
        return "cg";
        break;
    case 'h':
        return "ZA";
        break;
    case 'i':
        return "cQ";
        break;
    case 'j':
        return "YQ";
        break;
    case 'k':
        return "eA";
        break;
    case 'l':
        return "dw";
        break;
    case 'm':
        return "cw";
        break;
    case 'n':
        return "ag";
        break;
    case 'o':
        return "eQ";
        break;
    case 'p':
        return "bA";
        break;
    case 'q':
        return "aA";
        break;
    case 'r':
        return "ZQ";
        break;
    case 's':
        return "cA";
        break;
    case 't':
        return "Yw";
        break;
    case 'u':
        return "eg";
        break;
    case 'v':
        return "bg";
        break;
    case 'w':
        return "aq";
        break;
    case 'x':
        return "bQ";
        break;
    case 'y':
        return "Yg";
        break;
    case 'z':
        return "Zw";
        break;
    default:
        return " ";
        break;
    }
}
}

string enc(string input) {
string sketchyBois = input;
string bigBoi = "";
int yeetL = sketchyBois.length() + 1;
for (int x = 0; x < yeetL;) {
    bigBoi = bigBoi + reet(sketchyBois[x]);
    x++;
}
return bigBoi;
}

I was just wondering if anyone can tell me why it is doing this? Thank you!

One problem is that your loop over `sketchyBois` goes out of bounds of the string. — Some programmer dude, Nov 21 '18 at 14:41
Please read about [mcve]. If all the `24` letters are not necessary to reproduce the problem you should remove it from the code — 463035818_is_not_an_ai, Nov 21 '18 at 14:42
On an unrelated note, why don't have `++x` in the `for` loop statement itself? Like `for (int x = 0; x < sketchyBois.length(); ++x)`? — Some programmer dude, Nov 21 '18 at 14:42
`if (isspace(reet) == true)` -> `if (isspace(reet))` (`isspace` only returns a non-zero `int` value, not specifically `true`) — Paul R, Nov 21 '18 at 14:43
@user463035818 Sorry should have been more clear, my comment was about the `isspace` link. — Some programmer dude, Nov 21 '18 at 14:45
@Someprogrammerdude ah ok, completely agree, my mistake to jump in trying to answer what I was in fact not able to know — 463035818_is_not_an_ai, Nov 21 '18 at 14:46
The place to start when a function isn't behaving the way you expect it to is with the [documentation](https://en.cppreference.com/w/cpp/string/byte/isspace). Even better: read the documentation before you write code. — Pete Becker, Nov 21 '18 at 14:54

score 7 · Answer 1 · answered Nov 21 '18 at 14:44

7

You need to change

if (isspace(reet) == true)

to

if (isspace(reet))

or

if (isspace(reet) != 0)

since isspace only returns a non-zero int value for a white space character, not a bool.

(Note that as a matter of coding style, it's generally preferred to omit comparison with true or false in boolean tests and just use if (expr) or if (!expr).)

answered Nov 21 '18 at 14:44

Paul R

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2

Another fun trick: `if (!!isspace(reet) == true)` will also work as `!!` forces the conversion from a numerical value to a boolean value. (Don't actually do this though) – NathanOliver Nov 21 '18 at 14:49
4

@NathanOliver: yes - a great way to befuddle your colleagues who have never seen the "bang bang operator" before too! ;-) – Paul R Nov 21 '18 at 14:50
In applications where it matters, evaluating against zero is generally more efficient. – Jim Fell Nov 21 '18 at 14:50
It's more than just a matter of coding style; it is flat-out wrong to directly compare to `true` or `false`. It shows a fundamental misunderstanding of how an `if` statement evaluates an expression. – Mike Borkland Nov 21 '18 at 14:57
Paul R that didn't work. It still stops running after the space. For example the input I am a big boi returns just cQ. – NipIsTrue Nov 21 '18 at 15:34
@NipIsTrue With that change,`enc("I am a big boi")` produces `IAZgcwIAZgIAdAcQcgIAdAeQcQ ` (with a leading space). ([Example](http://coliru.stacked-crooked.com/a/9a4f4ec192217be8).) The problem lies in how you're reading the input before passing it to `enc`. – molbdnilo Nov 21 '18 at 16:04
Ok. How do you think i can fix that. – NipIsTrue Nov 21 '18 at 16:07
1

Since you're now looking at a second problem outside the code you've shown us you should post a new question with a [mcve] that reproduces this new problem. – Paul R Nov 21 '18 at 16:38
@molbdnilo I am passing the input as a string, inputed by the user. – NipIsTrue Nov 22 '18 at 16:51
1

@NipIsTrue I suspect that you're reading with `>>`, which reads word by word, separated by whitespace. – molbdnilo Nov 22 '18 at 17:08
@molbdnilo is there an alternate way to do it? – NipIsTrue Nov 23 '18 at 00:28
1

@NipIsTrue You should use `getline`. And perhaps get one of [these](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). – molbdnilo Nov 23 '18 at 07:30

Why doesn't this program detect that there is a whitespace?

1 Answers1