//Using both integers and ranges as list subscripts OK when within existing list size... list = ['a','b','c']; list[1] = 'x'; assert list == ['a','x','c'] list = ['a','b','c']; list[3] = 'x'; assert list == ['a','b','c','x'] list = ['a','b','c']; list[1..2] = ['x','y']; assert list == ['a','x','y'] //but only integers OK when outside existing list size... list = ['a','b','c']; list[4] = 'x'; assert list == ['a','b','c',null,'x'] //Ranges as list subscripts outside existing list size cause an out-of-bounds exception... list = ['a','b','c']; try{ list[2..3] = ['x','y'] }catch(Throwable e){ assert e instanceof IndexOutOfBoundsException } list = ['a','b','c']; try{ list[4..5] = ['x','y'] }catch(Throwable e){ assert e instanceof IndexOutOfBoundsException } //The desired behavior is: list = ['a','b','c']; list[2..3] = ['x','y']; assert list == ['a','b','x','y'] list = ['a','b','c']; list[4..5] = ['x','y']; assert list == ['a','b','c',null,'x','y']