/*
This method evaluates the element using the first and second value
and returns the result value. If the second operand type is missing
then return a missing value. If it is a number, check if it is an
absolute number (equal to its trucated value), and return the element
at that index using the Index method. If it isnt a number or missing,
then check the first elements type. If it is missing return missing
otherwise return null value.
*/
func (this *Element) Apply(context Context, first, second value.Value) (value.Value, error) {
switch second.Type() {
case value.NUMBER:
s := second.Actual().(float64)
if s == math.Trunc(s) {
v, _ := first.Index(int(s))
return v, nil
}
case value.MISSING:
return value.MISSING_VALUE, nil
}
if first.Type() == value.MISSING {
return value.MISSING_VALUE, nil
} else {
return value.NULL_VALUE, nil
}
}