CODEWITHSUNDEEP
c
user1427661
user1427661

Reputation: 11784

Check if a character is a space

I'm creating an absurdly simple program in C to mess around with getchar(). The program will print out what you input until you press enter and it will guarantee that your lines are no more than 80 chars each. To do this, I keep a running count of how many characters have been entered. Once the char count hits 70, the next space encountered will cause a line break. If no space is encountered between 70-80, a line break will occur regardless. I realize this is a super naive implementation and could be optimized left and right, but remember, I'm just messing around: 

while ((c = getchar()) != '\n') {
    if (lineLengthCount < 70) {
        putchar(c);
        lineLengthCount++;
    }   
    else if (lineLengthCount < 80 && (c == ' ')) {
        printf("%c\n", c); 
        lineLengthCount = 0;
    }   
    else {
        printf("%c\n", c); 
        lineLengthCount = 0;
    }   
}

The problem is the c == ' ' conditional doesn't seem to be actually checking for a space. I get output like this: 

fitter happier more productive comfortable not drinking too much regula
r exercise at the gym three days a week getting on better with your ass
ociate employee contemporaries at ease eating well no microwaved dinner

where I was hoping that the lines would be truncated when a space was encountered. Instead, no matter what character is entered after line 70, a new line is created. am I missing something? Does ' ' really mean any character?

Upvotes: 5

Views: 44669

Answers (4)

Metabble
Metabble

Reputation: 11841

while ((c = getchar()) != '\n') {
    if (lineLengthCount < 70) {
        putchar(c);
        lineLengthCount++;
    }   
    else if (lineLengthCount < 80 && (c == ' ')) {
        printf("%c\n", c); 
        lineLengthCount = 0;
    }   
    else if (lineLengthCount >= 80){
        printf("%c\n", c); 
        lineLengthCount = 0;
    }
    else{
        putchar(c);
        lineLengthCount++;
    }
}

I think this should work. That should prevent the else from executing when there are less than 80 characters but the character isn't a space.

EDIT: I realized now that instead if lineLengthCount is less than 80 but the character isn't a space it wouldn't get printed at all, so I added another else at the end to fix it.

Wouldn't this be shorter and more concise?

while ((c = getchar()) != '\n') {
    putchar(c);
    if((c == ' ' && lineLengthCount >= 70) || lineLengthCount >= 80){
        printf("\n");
        lineLengthCount = 0;
    }
    else
        ++lineLengthCount;
}

Upvotes: 5

tom1990
tom1990

Reputation: 642

Using ' ' is completely valid. You could also try using the C standard library function isspace() to check if the character is a space. This function returns a boolean expression, As in:

char ch = '0';

if (isspace(ch))
    //the char is a space...

By 'is space' this function actually means is any 'whitespace' character, so that includes '\n' or any other character that prints as empty space.

You could also the decimal value 32 which means the same as a space:

if (ch==32)

However for readability I would rather use the first version!

Upvotes: 1

KevinM
KevinM

Reputation: 577

If you're at all unsure of what's going on, I would recommend breaking up the "if" conditional into three explicit checks:

while ((c = getchar()) != '\n') {
    lineLengthCount++;
    if (lineLengthCount < 70) {
        putchar(c);
    }   

    if (lineLengthCount < 80 && (c == ' ')) {
        printf("%c\n", c); 
        lineLengthCount = 0;
    }   

    if (lineLengthCount == 80) {
        printf("%c\n", c); 
        lineLengthCount = 0;
    }   
}

If you want to see what's happening, write some debugging output in each "if" to notice when it is called.

Once it works, and you understand why, you can edit it down and combine the "ifs" ...

Upvotes: 1

molnarm
molnarm

Reputation: 10031

There's a problem with your conditions: if lineLengthCount is > 70 but the next character is not a space, the last else will be hit, breaking line and resetting the counter.

Upvotes: 4

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