Avoiding all these IF statements

Programming Questions

David Wil..

Avoiding all these IF statements

in Programming Questions • 2 years ago

Hi all,

I'm using this function every time in draw() and it just feels wrong . I'm sure there's a more efficient/elegant way.

The numbers returned from the array vary depending on various things so that's no so important, what I'd really like is to not use all these IF statements.

Would be very interested to hear your thoughts

Thanks

Dave

int calculateHeights(int i) {
  if (x < i && x > i-4) {
    index = 0;
  }
  if (x < i-4 && x > i-8) {
    index = 1;
  }
  if (x < i-8 && x > i-12) {
    index = 2;
  }
  if (x < i-12 && x > i-16) {
    index = 3;
  }
  if (x < i-16 && x > i-20) {
    index = 4;
  }
  if (x < i-20 && x > i-24) {
    index = 5;
  }  
  if (x < i-24 && x > i-28) {
    index = 6;
  }  
  if (x < i-28 && x > i-32) {
    index = 7;
  }  
  if (x < i-32 && x > i-36) {
    index = 8;
  }  
  if (x < i-36 && x > i-40) {
    index = 9;
  }  
  if (x < i-40 && x > i-44) {
    index = 10;
  }  
  if (x < i-44 && x > i-48) {
    index = 11;
  }  
  if (x < i-48 && x > i-52) {
    index = 12;
  }  
  if (x < i-52 && x > i-56) {
    index = 13;
  }  
  if (x < i-56 && x > i-60) {
    index = 14;
  }
  if (x < i-60 && x > i-64) {
    index = 15;
  }
  return heights[index];
}

Replies(3)

noncom

Re: Avoiding all these IF statements

2 years ago

maybe something like this?:

for (int i = 0; i > -64; i-= 4){
if(x > i - 4 && x < i){
index = - i / 4;
break;
}
}

But something tells me that you are dealing with powers of two... i am sure there are much more more correct ways to do this, say as finding an index of a lonely 1 in a 64-bit value full of zeroes... anyway, you should have told about WHAT EXACTLY are you trying to achieve, so that we may see for even a better approach

BTW - use the "code highlight" tag so that your could would stay withing the page limits and still be readable..

davbol

Re: Avoiding all these IF statements

2 years ago

your values run in increments of 4, based solely on the difference between i and x. with one special exception: it appears you are specifically excluding the "differ by exactly 4 multiples", is that by design or just an oversight? for instance what happens when x==i-4, it falls through all your if statements, so what is the value of index then??

perhaps (?) all you want is something like:

index = (i-x)/4;

David Wil..

Re: Re: Avoiding all these IF statements

2 years ago

Oh my god

index = (i-x)/4;

Will do very nicely, thank you.

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