func evalSubscript(ec *evalCtx, left, right Value, lp, rp parse.Pos) Value {
var sub string
if s, ok := right.(str); ok {
sub = string(s)
} else {
ec.errorf(rp, "right operand of subscript must be of type string")
}
switch left.(type) {
case *table:
t := left.(*table)
// TODO(xiaq): An index is considered a list index if it can be parsed
// as an unsigned integer; otherwise it is a dict index. This is
// somewhat subtle.
idx, err := strconv.ParseUint(sub, 10, 0)
if err == nil {
if idx < uint64(len(t.List)) {
return t.List[idx]
}
ec.errorf(rp, "index out of range")
}
if v, ok := t.Dict[sub]; ok {
return v
}
ec.errorf(rp, "nonexistent key %q", sub)
return nil
case str:
invalidIndex := "invalid index, must be integer or integer:integer"
ss := strings.Split(sub, ":")
if len(ss) > 2 {
ec.errorf(rp, invalidIndex)
}
idx := make([]int, len(ss))
for i, s := range ss {
n, err := strconv.ParseInt(s, 10, 0)
if err != nil {
ec.errorf(rp, invalidIndex)
}
idx[i] = int(n)
}
var s string
var e error
if len(idx) == 1 {
var r rune
r, e = strutil.NthRune(toString(left), idx[0])
s = string(r)
} else {
s, e = strutil.SubstringByRune(toString(left), idx[0], idx[1])
}
if e != nil {
ec.errorf(rp, "%v", e)
}
return str(s)
default:
ec.errorf(lp, "left operand of subscript must be of type string, env, table or any")
return nil
}
}
func (s String) Index(idx Value) Value {
i := intIndex(idx)
r, err := strutil.NthRune(string(s), i)
maybeThrow(err)
return String(string(r))
}