Problem with outer join if tolerance is large

[jorainer]

I stumbled across the following problem:
performing an outer join on the two vectors below with a tolerance of 3 I would expect to have one match more than what we get:

x <- c(1, 1.5, 2, 2.1, 5, 6, 7)
y <- c(4.6, 4.7, 4.8, 4.9, 5, 6, 7, 8)

MsCoreUtils:::.joinOuter(x, y, 3, 0)
$x
 [1]  1  2  3  4 NA NA NA NA  5  6  7 NA

$y
 [1] NA NA NA NA  1  2  3  4  5  6  7  8

In fact, I would expect to see a match also between x[4] and y[1] (i.e. 2.1 and 4.6).
While this is a special case and in real-life spectra comparisons we might not have this case I would still want to fix that. I am currently checking if I could get it fixed in the C implementation of the outer join.