Power By 专否社区

Will else-is resolve if the if statement above it is chosen?

Go To StackoverFlow.com

0

In this set of statements:

if(robot1Count < 12) {
    robot1Count++;
}
else if(robot1Count < 24) {
    robot1Count++;
}
else if(robot1Count < 36) {
    robot1Count++;
}
else if(robot1Count < 48) {
    robot1Count++;
}
else {
    robot1Count = 0;
}

Imagine this is in an infinite loop, would this loop traverse from 0 to 48, change to 0. The thing I'm wondering is if the first block is executed, would all the following blocks be ignored? Or should I change the second to else if(robot1Count < 24 && robot1Count >= 12) ? Or does that not matter?

2012-04-03 20:16
by Portaljacker
Why don't you run it and find out - Oliver Charlesworth 2012-04-03 20:17
It will only enter one statement. What are you trying do to exactly - Mysticial 2012-04-03 20:17
What is this, a theory question? Or don't you have a compiler? Or are you too lazy to test some simple code - Kendall Frey 2012-04-03 20:27

7

The thing I'm wondering is if the first block is executed, would all the following blocks be ignored?

Yes, they will all be ignored. The conditions won't even be evaluated. But you know, you could have tested this yourself!

if(robot1Count < 12) {
    printf("< 12");
    robot1Count++;
}
else if(robot1Count < 24) {
    printf(">= 12 && < 24");
    robot1Count++;
}
else if(robot1Count < 36) {
    printf(">= 24 && < 36");
    robot1Count++;
}
else if(robot1Count < 48) {
    printf(">= 36 && < 48");
    robot1Count++;
}
else {
    printf(">= 48");
    robot1Count = 0;
}

And then you can see which messages are printed to the console and then you'd know and feel what is going on!

2012-04-03 20:17
by jason

4

This:

if (cond1)
    stuff1;
else if (cond2)
    stuff2;
else if (cond3)
    stuff3;
else
    stuff4;

is identical to this:

if (cond1) {
    stuff1;
}
else {
    if (cond2) {
        stuff2;
    }
    else {
        if (cond3) {
            stuff3;
        }
        else {
            stuff4;
        }
    }
}
2012-04-03 20:19
by Oliver Charlesworth
Oli, you beat me to it - Mark Ransom 2012-04-03 20:22

2

Yes -- the if leg and the else leg of an if statement are mututally exclusive -- if the if leg executes the else does not (and vice versa).

2012-04-03 20:20
by Jerry Coffin

1

Of course they will be ignored, unless you switch the "else if" to "if"

2012-04-03 20:18
by idish
Of course? If it truly were "of course" there would be no question here - jason 2012-04-03 20:24
@Jason You are right, I shouldn't have to said it - idish 2012-04-04 04:31

1

if the code above is in a infinite loop

example

int robot1Count = 0;
while (1 != 2) {

if(robot1Count < 12) {
    robot1Count++;
}
else if(robot1Count < 24) {
    robot1Count++;
}
else if(robot1Count < 36) {
    robot1Count++;
}
else if(robot1Count < 48) {
    robot1Count++;
}
else {
    robot1Count = 0;
}
}

in a loop this will increment to 48 and go back to 0

it will only hit robot1Count++ per single execution of the loop

2012-04-03 20:23
by nate_weldon
Can't say I've ever seen someone use while (1 != 2) over the likes of while (1) or while (true). Is there a specific reason (like another language) for that - chris 2012-04-03 21:00
Ads