Added control to prevent invalid low/high ranges

inclusives.go

@@ -1,15 +1,22 @@
 package interval
 
-func (intvls *intervals) getInclusives(intervalLow, intervalHigh int) (int, int) {
+import (
+	"fmt"
+)
+
+func (intvls *intervals) getInclusives(intervalLow, intervalHigh int) (int, int, error) {
 	low := intvls.getInclusiveLow(intervalLow)
 	high := intvls.getInclusiveHigh(intervalHigh)
-	if high < low {
-		high = low
-	}
+
+	// if we get an incoherent result it's because it's invalid, for example in this case:
+	//		(low,high)=(0,1) --> if we add 1 to the Low and substract 1 to the High ends with (1,0) which is not valid
 	if low > high {
-		low = high
+		return 0, 0, fmt.Errorf("low (%v) can not be bigger than high (%v)", low, high)
 	}
-	return low, high
+	if high < low {
+		return 0, 0, fmt.Errorf("high (%v) can not be smaller than low (%v)", high, low)
+	}
+	return low, high, nil
 }
 
 func (intvls *intervals) getInclusiveLow(value int) int {