explain these how the conditional operator helps in counting the negative and positive numbers in an array?

Question

my confusion is that how in the program the number of positive and negative numbers are calculated by writing that piece of code shown. explain these code please!

int num[5], i, neg = 0, pos = 0;

printf("enter any 5 numbers");
for (i = 0; i <= 4; i++)
    scanf("%d", &num[i]);
for (i = 0; i <= 4; i++) {
    num[i] < 0 ? neg++ : (pos++);
}
printf("\nnegative elements=%d", neg);
printf("\npositive elements=%d", pos);
getch();

As for your problem, you *do* know how the [ternary (conditional) expression](https://stackoverflow.com/questions/758849/the-ternary-conditional-operator-in-c) works? — Some programmer dude, Jul 04 '17 at 07:38
The ternary operator works as follows: `condition ? execute if true : execute if false`. — Andre Kampling, Jul 04 '17 at 07:45
`num[i]<0?neg++:(pos++);` ---> `if (num[i]<0) neg++; else pos++;` — LPs, Jul 04 '17 at 07:45
okay! but what neg++ do to give the printf statement the number of negative number. — Muktesh, Jul 04 '17 at 07:46
Well, you should by a good c book and look at increment and if condition.... — LPs, Jul 04 '17 at 07:48
maybe you are right, i have a book not able to find it there and thought will get a quick answer here — Muktesh, Jul 04 '17 at 07:49
It actually doesn't do anything meaningful to help. It's just used as syntactic sugar to replace a proper if statement. This code fails code review in my book. It's worse than the if, since operator precedence can make it fail gloriously. That's why `pos++` is in parentheses. — StoryTeller - Unslander Monica, Jul 04 '17 at 07:50
lol i am getting it now every time neg++ is true neg is incremented by 1! — Muktesh, Jul 04 '17 at 07:53

score 1 · Answer 1 · answered Jul 04 '17 at 07:46

1

 num[i]<0?neg++:(pos++);

Here, If number less then zero then condition become true and count the negative numbers and If number not less then zero then condition become false and count positive numbers.

answered Jul 04 '17 at 07:46

msc

33,420
29
119
214

score 1 · Answer 2 · answered Jul 04 '17 at 07:50

1

The line

num[i]<0?neg++:(pos++);

means- compare num[i] to 0, if it is lower, increase the variable neg. Otherwise (num[i] >= 0), increase the variable pos.

hope this helps

answered Jul 04 '17 at 07:50

Inbaral

59
10

score 0 · Answer 3 · answered Jul 04 '17 at 08:07

0

Since, most answers have explained the ternary operator, I need not do it again. The neg++ post-increments the previous value of neg variable. And the same goes for pos++. Here's a link on post/pre increments.

answered Jul 04 '17 at 08:07

WhiteSword

101
9

score 0 · Answer 4 · answered Jul 04 '17 at 08:40

The ternary operator used as an expression statement evaluates like an if statement:

num[i] < 0 ? neg++ : (pos++);

is equivalent to

if (num[i] < 0)
    neg++;
else
    pos++;

This kind of coding is not considered good style, and there are other issues in the code fragment posted:

the return value of scanf() should be checked to avoid undefined behavior if the input cannot be converted to an int.
the loop index should be compared to the array size with i < 5 instead of using the <= operator and a close but different constant.
output lines should be terminated with newline, not initiated with one.
getch() is a non standard function. Its purpose is to force a pause before the program exits. Fixing shortcomings of the environment inside the program is a sad workaround. Opening a terminal window to execute programs is a better alternative: it allows the programmer to observe all program output including any extra runtime messages occurring upon program termination.

Thanks for these valuable tips, i'm little confused about how to check the scanf() return value and last one how to open a terminal window to execute program. — Muktesh, Jul 06 '17 at 05:27
`scanf()` returns the number of successful conversions. In your case it should return `1` if an integer number was stored into `num[i]`. To open a terminal window, in Windows use the start menu, run, `cmd.exe`. — chqrlie, Jul 06 '17 at 07:06

explain these how the conditional operator helps in counting the negative and positive numbers in an array?

4 Answers4