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I'm trying to trouble shoot a problem with my code and narrowed it down to my if statement not working with a fraction.

The below code does not work and returns 0

for(float i=0; i <= 1; i += .0001){
 t += .0001;
 if(t >= 1/440){ //Fraction
   t = 0;
 }
 Serial.println(t*100);
 delay(100);
}

But when I replace the 1/440 with its decimal equivalent (.0022727) it works fine and counts from 0 to 2.2

for(float i=0; i <= 1; i += .0001){
 t += .0001;
 if(t >= 0.0022727){ //Decimal
   t = 0;
 }
 Serial.println(t*100);
 delay(100);
}

If there is a simple way to use a fractional value instead of a decimal value it would make my application much similar. Thanks.

6
  • 1
    Always present float calculations like this 1.0/440.0 and not 1/440 to prevent these being treated as integer calculations. Avoid using floats in comparisons especially '==' comparisons.
    – 6v6gt
    Commented Apr 26, 2023 at 4:27
  • 1
    @6v6gt Please read When shouldn't I comment?. If you aren't requesting clarification from the author (or the other couple of reasons to comment on the question) then you should be posting an answer instead.
    – Nick Gammon
    Commented Apr 26, 2023 at 5:40
  • 1
    @6v6gt You may want to look at this. I don't know if it will matter being as old as it is, but you could weigh in on it if you have the interest; I don't. But I would them to make up their minds about it.
    – timemage
    Commented Apr 26, 2023 at 15:18
  • 1
    @NickGammon One problem with giving a formal answer in such a borderline off topic case (this one could fail if the often applied test "non-Arduino specific" is applied and it does anyway have a general C/C++ look to it) is that the answerer risks losing a couple of Brownie points if someone decides to assert that it is off topic and starts down-voting both the question and the answer. Some answers which I have put considerable effort into, and the OP could not have known that the solution to the problem was "Non-Arduino specific", have ended up with a -1 score.
    – 6v6gt
    Commented Apr 27, 2023 at 18:22
  • @6v6gt Yeah, I agree. I try to ignore the occasional down-vote as there are people who like to nitpick that sort of stuff. It's true it's really a programming question, but we do have a programming tag after all, so I think programming questions are OK. Especially if beginners to Arduino maybe think that the Arduino has different rules to C++.
    – Nick Gammon
    Commented Apr 27, 2023 at 21:51

1 Answer 1

2

1/440 will be treated as an integer expression, returning zero.

To make it work, make one or both operands a floating-point type. In your case:

 if(t >= (float)1 / 440){ //Fraction
   t = 0;
 }

Or:

 if(t >= 1.0/440){ //Fraction
   t = 0;
 }

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