muesli/signature.go

package muesli

/*
ParametersPerSignature is the amount of parameters that will be
checked when type checking a signature.	Limited mosty to allow hashability, 
that is, Signature is a map key.
*/
const ParametersPerSignature = 32

/* Parameter describes the name and type of a parameter of a command. */
type Parameter struct {
	Name WordValue
	Type TypeValue
}

// Signature describes the types of the arguments that a callable takes. */
type Signature struct {
	Parameters [ParametersPerSignature]Parameter
}

func (s Signature) String() string {
	res := "["
	sep := ""
	for _, param := range s.Parameters {
        typ := param.Type
		if typ != ZeroTypeValue { 
			res = res + sep + typ.String()
			sep = " "
		}
	}
	res = res + "]"
	return res
}

func NewSignature(types ... TypeValue) Signature {
    signature := Signature{}
    for i := 0 ; i < len(types) && i < len(signature.Parameters) ; i ++ {
        signature.Parameters[i].Type = types[i]
    }
    return signature
}

// NoSignature is the default signature which means the VM will not do 
// any argument type checking when the callable is called.
func NoSignature() Signature { 
	return Signature{}
}

func CalculateSignature(arguments ...Value) Signature {
	signature := Signature{}
	for i := 0; i < len(signature.Parameters); i++ {
		if i < len(arguments) {
			signature.Parameters[i].Type = arguments[i].Type()
		} else {			
			signature.Parameters[i].Type = AnyTypeValue
		}
	}
	return signature
}

func (tv TypeValue) IsMatch(other TypeValue) bool {
	if tv == AnyTypeValue || other == AnyTypeValue {
		return true
	}
	if tv == ZeroTypeValue || other == ZeroTypeValue {
		return true
	}
	return tv == other
}

func (signature Signature) IsMatch(other Signature) bool {
	for i, param := range signature.Parameters {
		t1 := param.Type
		t2 := other.Parameters[i].Type
		if !t1.IsMatch(t2) {
			return false
		}
	}
	return true
}