How can this be true? (<) operator not working

I noticed there had to be a bug in some of my code so I went into the debugger. While in the debugger I noticed a while loop not terminating when it was supposed to. Here is the root of the problem:

increment =

   1.0000e-01

K>> increment < .1

ans =

     1

How can this be happening?

[Jason]

some extra information

format hex

.1 =

3fb999999999999a

increment =

3fb9999999999999

Why is this happening and what can I do? Thanks.

Answer 1

[James Tursa]

0.1 cannot be represented exactly in IEEE double precision floating point format. Welcome to the world of floating point arithmetic. You will have to adjust your algorithms (e.g., use tolerances on comparisons, etc) to account for this effect.

[James Tursa]

P.S. If you want to see the exact decimal conversion for any IEEE double or single number you can use this utility:

http://www.mathworks.com/matlabcentral/fileexchange/22239-num2strexact-exact-version-of-num2str

Answer 2

[Sean de Wolski]

FAQ6.1