Why is this an issue?
Floating point math is imprecise because of the challenges of storing such values in a binary representation. Even worse, floating point math is
not associative; push a
float or a
double through a series of simple mathematical operations and the answer will be
different based on the order of those operation because of the rounding that takes place at each step.
Even simple floating point assignments are not simple:
float f = 0.100000001f; // 0.1
double d = 0.10000000000000001; // 0.1
(Results will vary based on compiler and compiler settings)
Therefore, the use of the equality (
==) and inequality (
!=) operators on
is almost always an error.
This rule checks for the use of direct and indirect equality/inequality tests on floats and doubles.
Noncompliant code example
float myNumber = 3.146f;
if ( myNumber == 3.146f ) //Noncompliant. Because of floating point imprecision, this will be false
if (myNumber <= 3.146f && mNumber >= 3.146f) // Noncompliant indirect equality test
if (myNumber < 4 || myNumber > 4) // Noncompliant indirect inequality test