MATLAB: Very simple ‘if’ statement with == operator not working

==bugifisequaloperatorsimplestatement

I have some very basic logic that is not working. It's a simple 'if' statement with an '==' operator. Please help.
Program:
%simple_script.m
clear all
A = 0.40;
B = 0.20;
C = 0.60;
D = A + B;
        if C == D
            disp('It worked.')
        else
            disp('It did not work.')
        end
Command Window:
    >> simple_script
    It did not work.
    >>

Best Answer

Welcome to the apparent inconsistencies of floating-point calculations. See the discussion in Why is 0.3 - 0.2 - 0.1 (or similar) not equal to zero? (link) for more informaiton.
Floating point approximations are similar in this regard to decimal 1/3 being approximated as 0.3333... Multiplying by 3 then gives 0.9999..., not 1.
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