why is simulink matlab function block failing to evaluate a < operator correctly

I have a simply if else statment using <= and < operators. I have a situation where my code is incorrectly evaluating "remainder < Tfs*2" as true when the two values are 0.00004.

    elseif (Tfs <= remainder & remainder < Tfs*2)
        remainder < (Tfs*2)                             % this evaluates to 1
        fprintf('%.15f, %.15f\n', remainder, Tfs*2);    % output is 0.000040000000000, 0.000040000000000
        vector = 1;
    elseif (Tfs*2 <= remainder && remainder < Tfs*3)

Answer 1

[Walter Roberson]

0.000040000000000 is not enough digits of printout to see whether the two are equal or not.

4.00000000000000032721221565612523818344925530254840850830078125e-05

and

3.9999999999999996495858578526849669287912547588348388671875e-05

will both print out as 0.000040000000000 but are not equal.

You should either grab num2strexact from the File Exchange or you should print out

remainder - Tfs*2

You should also consider assigning Tfs*2 to a variable so that you avoid evaluating it multiple times. Floating point values calculated by even slightly different methods are permitted to give different results.

[Robert Garton]

Thanks Walter you were spot on. The value ended up being 0.000039999999999999434065981602.

Thanks for your help.