func buildFor(f *algebra.UpdateFor, val value.Value, arrays []value.Value, context *Context) ([]value.Value, error) {
n := -1
for _, a := range arrays {
act := a.Actual()
switch act := act.(type) {
case []interface{}:
if n < 0 || len(act) < n {
n = len(act)
}
}
}
if n < 0 {
return nil, nil
}
rv := make([]value.Value, n)
for i, _ := range rv {
rv[i] = value.NewScopeValue(make(map[string]interface{}, len(f.Bindings())), val)
for j, b := range f.Bindings() {
v, ok := arrays[j].Index(i)
if ok {
rv[i].SetField(b.Variable(), v)
}
}
}
return rv, nil
}
func arraysFor(f *algebra.UpdateFor, val value.Value, context *Context) ([]value.Value, error) {
var err error
arrays := make([]value.Value, len(f.Bindings()))
for i, b := range f.Bindings() {
arrays[i], err = b.Expression().Evaluate(val, context)
if err != nil {
return nil, err
}
if b.Descend() {
buffer := make([]interface{}, 0, 256)
arrays[i] = value.NewValue(arrays[i].Descendants(buffer))
}
}
return arrays, nil
}