precision in seq

Hi everybody,

this is a warning more than a question.

I noticed that seq produces approximate results:

seq(0,1,0.05)[19]==0.9

[1] TRUE

seq(0,1,0.05)[20]==0.95

[1] FALSE

seq(0,1,0.05)[21]==1

[1] TRUE

seq(0,1,0.05)[20]-0.95

[1] 1.110223024625157e-16

I do not understand why 0.9 and 1 are correct (within some
tolerance or strictly exact?)  and 0.95 is not.

this one works:

((0:20)/20)[20]==0.95

[1] TRUE

Eric Elguero