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Discrepancy: number comparison differs from Processing Java `(0.1 + 0.2 == 0.3)`

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Quiet
Tech stack
java, python, rust
Domain
backend

Research direction

Run the provided Processing Java and mewnala Python sketches to confirm the differing results. Then trace the numeric evaluation behavior in the Rust implementation and determine whether the discrepancy should be fixed or documented, with a test or documentation update defining the expected behavior.

Written by the indexing model from the issue text.

Description

I don't know whether this is something that needs to be addressed or just documented.
I suppose this is related to the difference between float and double precision (?)

In Processing, this condition evaluates to true:

void setup() {
  size(400, 400);

  if (0.1 + 0.2 == 0.3) {
    background(0, 255, 0);
    circle(200, 200, 100);
  }
}

The equivalent mewnala sketch evaluates the condition as false.

from mewnala import *

def setup():
    size(200, 200)

    if 0.1 + 0.2 == 0.3:
        background(0, 255, 0)
        circle(200, 200, 100)

run()

Note: size is reduced in mewnala to account for https://github.com/processing/libprocessing/issues/198

Image
Dominant language
Rust
Stars
69
Forks
14
Avg merge
15d 22h
Merged PRs (30d)
3

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