Better fix for tricky FP arithmetic, again for #1006.

R/foverlaps.R

@@ -90,8 +90,13 @@ foverlaps <- function(x, y, by.x = if (!is.null(key(x))) key(x) else key(y), by.
         mcall = make_call(mcols, quote(c))
         if (type %chin% c("within", "any")) {
             mcall[[3L]] = substitute(
-                if (isposix) unclass(val)*incr
-                else if (isdouble) (val+dt_eps())*incr # fix for #1006 - 0.0 occurs in both start and end
+                if (isposix) unclass(val)*incr # incr is okay since this won't be negative
+                else if (isdouble) {
+                    # fix for #1006 - 0.0 occurs in both start and end
+                    # better fix for 0.0, and other -ves. can't use 'incr'
+                    # hopefully this doesn't open another can of worms
+                    (val+dt_eps())*(1 + sign(val)*dt_eps()) 
+                }
                 else val+incr, 
                 list(val = mcall[[3L]], incr = incr))
         }

inst/tests/tests.Rraw

@@ -5774,7 +5774,20 @@ dt.ref <- data.table(start=x[-n], end=x[-1], key=c("start", "end"))
 dt.query <- data.table(q1=c(-0.2, -0.05, 0.05, 0.15), q2=c(-0.2, -0.05, 0.05, 0.15), key=c("q1", "q2"))
 ans=cbind(dt.ref[, .(start,end)], dt.query[2:3, .(q1,q2)])
 setkey(ans, q1,q2)
-test(1468, foverlaps(dt.query, dt.ref, nomatch=0L), ans)
+test(1468.1, foverlaps(dt.query, dt.ref, nomatch=0L), ans)
+# fix and additional tests for #1006 following OP's follow-up.
+dt1 = data.table(x=c(-6.36917800737546, -2.19964384651646),
+                 y=c(-2.19964384651646, 4.07116428752538))
+dt2 = data.table(x= 2.91816502571793, y=2.91816502571793)
+setkey(dt1)
+setkey(dt2)
+test(1468.2, foverlaps(dt2, dt1, which=TRUE), data.table(xid=1L, yid=2L))
+dt1 = data.table(x=c(-6,-3), y=c(-3,4))
+dt2 = data.table(x=3,y=3)
+setkey(dt1)
+setkey(dt2)
+test(1468.3, foverlaps(dt2, dt1, which=TRUE), data.table(xid=1L, yid=2L))
+
 
 # Fix for #1010 (discovered while fixing #1007). Don't retain key if i had no key, but irows is sorted, and roll != FALSE... See example in #1010.
 require(data.table) ## 1.9.5