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C++ Coding Standard

Rule:  POR#025Checked automatically with code checker

Synopsis:Floating point values shall not be compared using the == or != operators
Severity Level:2


Due to rounding errors, most floating-point numbers end up being slightly imprecise. As long as this imprecision stays small, it can usually be ignored. However, it also means that numbers expected to be equal (e.g. when calculating the same result through different correct methods) often differ slightly, and a simple equality test fails. For example:

  float a = 0.15 + 0.15
  float b = 0.1 + 0.2
  if (a == b) // can be false!

Solutions to this problem that are not correct include:

  !(a < b) && !(a > b)


  fabs(a - b) < Double.Epsilon
Please read [Dawson] to understand how to solve this issue.

Literature References: