muesli/value.go

package muesli

// Value interface type for Muesli run time values that the language works with.
type Value interface {
	// String because a value must be convertible to string.
	// This string is then used as the hash key in MapValue and for debugging.
	String() string
	// Type returns the type of the value. Muesli has typed values.
	Type() TypeValue
	// Convert the value to a different go value which must be passed 
	// in as a pointer to which the value must be set, 
	// or return an error if the conversion is not possible.
	Convert(to interface{}) error
}

/* Helpers to easily convert Muesli values to "normal" Go values. */
func From(from Value, to interface{}) error {
	return from.Convert(to)
}

// ParseOptArgs is helper to easily convert Muesli value lists to "normal" 
// Go values. args is the input, required is the amount of required aruments, 
// and to are pointers to where to store the data. The args are converted by 
// calling the  Convert() method on them.
// The returned array contains the remaining unparsed arguments.
func ParseOptArgs(args []Value, required int, to...interface{}) ([]Value, error) {
	if required > len(args) {
		return nil, NewErrorValuef("Too few arguments, expected %d, got %d", required, len(args))
	}
    stop := len(args)
    if len(to) < stop {
        stop = len(to)
    }
	i:= 0
	for ; i < stop ; i ++ {
		fromElt := args[i]
		toElt 	:= to[i]
		if fromElt == nil {
			return nil, NewErrorValuef("Nil pointer to result %d", i)
		}
		err := fromElt.Convert(toElt)
		if err != nil {
			return nil, err
		}
	}
	rest := args[i:len(args)]
	return rest, nil
}

// ParseArgs is helper to easily convert Muesli value lists to "normal" 
// Go values.  It is the same as ParseOptArgs(args, len(to), to...)
func ParseArgs(args []Value, to...interface{}) ([]Value, error) {
	return ParseOptArgs(args, len(to), to...)
}

/* Helpers to easily convert Muesli value lists to "normal" Go values in slices. */
func ParseArgsToIntSlice(args []Value) ([]int, error) {
	res := []int{}
	for _, arg := range args{
		value := int(0)
		err := arg.Convert(&value)
		if err != nil  {
			return res, err
		}
		res = append(res, value)
	}
	
	return res, nil
}

/* Helpers to easily convert Muesli value lists to "normal" Go values in slices. */
func ParseArgsToFloat64Slice(args []Value) ([]float64, error) {
	res := []float64{}
	for _, arg := range args{
		value := float64(0.0)
		err := arg.Convert(&value)
		if err != nil  {
			return res, err
		}
		res = append(res, value)
	}
	
	return res, nil
}

/* Helpers to easily convert Muesli values from "normal" Go values. */
func To(from interface{}) Value {
	switch val := from.(type) {
	case string:
		return StringValue(val)
	case int8:
		return IntValue(val)
	case int16:
		return IntValue(val)
	case int32:
		return IntValue(val)
	case int64:
		return IntValue(val)
	case int:
		return IntValue(val)
	case bool:
		return BoolValue(val)
	case float32:
		return FloatValue(val)
	case float64:
		return FloatValue(val)
	case error:
		return ErrorValue{val}
	case Value:
		return val
	default:
		return NewErrorValuef("Cannot convert value %v", from)
	}
}

func ListTo(froms ...interface{}) []Value {
	list := make([]Value, 0)
	for _, from := range froms {
		val := To(from)
		list = append(list, val)
	}
	return list
}

func ListFrom(froms []Value, tos ...interface{}) error {
	for i, from := range froms {
		if i >= len(tos) {
			break
		}
		err := From(from, tos[i])
		if err != nil {
			return err
		}
	}
	return nil
}

func ListFromList(froms []Value) []interface{} {
	res := make([]interface{}, len(froms))
	for i, from := range froms {
		res[i] = from
	}
	return res
}

func Return(args ... Value) []Value {
	return args
}

func ReturnEmpty() []Value {
	return []Value{EmptyValue{}}
}

func ReturnError(err error) []Value {
	return []Value{ErrorValue{err}}
}

func Ok(args ... Value) []Value {
	return args
}

func Fail(err error) []Value {
	return []Value{ErrorValue{err}}
}

func None() []Value {
	return []Value{EmptyValue{}}
}

func BoolOk(b bool) []Value{
	return []Value{BoolValue(b)}
}

func IntOk(i int) []Value{
	return []Value{IntValue(i)}
}

func FloatOk(f float64) []Value{
	return []Value{FloatValue(f)}
}