func (v *evalConcat) Eval(s ast.Scope, stack *ast.Stack) (interface{}, ast.Type, error) {
// The expressions should all be on the stack in reverse
// order. So pop them off, reverse their order, and concatenate.
nodes := make([]*ast.LiteralNode, 0, len(v.Exprs))
for range v.Exprs {
nodes = append(nodes, stack.Pop().(*ast.LiteralNode))
}
var buf bytes.Buffer
for i := len(nodes) - 1; i >= 0; i-- {
buf.WriteString(nodes[i].Value.(string))
}
return buf.String(), ast.TypeString, nil
}
func (v *evalCall) Eval(s ast.Scope, stack *ast.Stack) (interface{}, ast.Type, error) {
// Look up the function in the map
function, ok := s.LookupFunc(v.Func)
if !ok {
return nil, ast.TypeInvalid, fmt.Errorf(
"unknown function called: %s", v.Func)
}
// The arguments are on the stack in reverse order, so pop them off.
args := make([]interface{}, len(v.Args))
for i, _ := range v.Args {
node := stack.Pop().(*ast.LiteralNode)
args[len(v.Args)-1-i] = node.Value
}
// Call the function
result, err := function.Callback(args)
if err != nil {
return nil, ast.TypeInvalid, fmt.Errorf("%s: %s", v.Func, err)
}
return result, function.ReturnType, nil
}