muesli/cover.go

package muesli

import "fmt"

/* An overload is an overloaded value that can be called. */
type Overload struct {
	Name string
	Callable
}

/* A cover is a callable that dispatches to other callables depending on
the types of the arguments, in particular the first one. The individual
callable functions are the overloads
*/
type CoverValue struct {
	BasicCallable
	Overloads map[Signature]Overload
}

func (cv CoverValue) String() string {
	res := fmt.Sprintf("cover %s [ ", cv.Name)
	for k, v := range cv.Overloads {
		res = fmt.Sprintf("%s [%v] %s", res, k, v.Name)
	}
	res = fmt.Sprintf("%s].", res)
	return res;
}

func NewCoverValue(name string) *CoverValue {
	result := &CoverValue{}
	result.Name = name
	result.Overloads = make(map[Signature]Overload)
	return result
}


func (cover *CoverValue) Help() string {
	help := cover.BasicCallable.Help()
	extra := "\n"
	for signature, overload := range cover.Overloads {
		// fmt.Printf("overload: %v", signature)
		extra = extra + fmt.Sprintf("* %v -> %s\n", signature.String(), overload.Name)
	}
	return help + extra
}



func (cover *CoverValue) Call(vm *VM, arguments ...Value) []Value {
	signature := CalculateSignature(arguments...)
	if overload, ok := cover.Overloads[signature]; ok {
		return overload.Call(vm, arguments...)
	} else {
		for overloadSignature, overload := range cover.Overloads {
			if signature.IsMatch(overloadSignature) {
				return overload.Call(vm, arguments...)
			}
		}
	}
	vm.Fail()
	return Fail(NewErrorValuef("Could not match cover %s with arguments: %s<->%v", cover.String(), signature, arguments))
}