nil_props.go

package props

import (
	"github.com/Syuparn/pangaea/object"
)

// NilProps provides built-in props for Nil.
// NOTE: Some Nil props are defind by native code (not by this function).
func NilProps(propContainer map[string]object.PanObject) map[string]object.PanObject {
	// NOTE: inject some built-in functions which relate to parser or evaluator
	return map[string]object.PanObject{
		"==": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				if len(args) < 2 {
					return object.NewTypeErr("== requires at least 2 args")
				}

				if _, ok := object.TraceProtoOfNil(args[0]); !ok {
					return object.BuiltInFalse
				}
				if _, ok := object.TraceProtoOfNil(args[1]); !ok {
					return object.BuiltInFalse
				}

				return object.BuiltInTrue
			},
		),
		"+": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				// anything can be added to nil (and nil works as zero value).
				if len(args) < 2 {
					return object.NewTypeErr("+ requires at least 2 args")
				}
				return args[1]
			},
		),
		"-": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				// anything can be subtracted from nil (and nil works as zero value).
				if len(args) < 2 {
					return object.NewTypeErr("- requires at least 2 args")
				}

				// return -args[1]
				return propContainer["Obj_callProp"].(*object.PanBuiltIn).Fn(
					env, object.EmptyPanObjPtr(),
					object.EmptyPanObjPtr(), args[1], prefixMinusSym,
				)
			},
		),
		"*": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				// anything can be multiplied by nil (and nil works as identity unit (1 for example)).
				if len(args) < 2 {
					return object.NewTypeErr("* requires at least 2 args")
				}
				return args[1]
			},
		),
		"/": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				// anything can be divided by nil (and nil works as 1).
				if len(args) < 2 {
					return object.NewTypeErr("/ requires at least 2 args")
				}

				// return 1 / args[1]
				return propContainer["Obj_callProp"].(*object.PanBuiltIn).Fn(
					env, object.EmptyPanObjPtr(),
					object.EmptyPanObjPtr(), object.NewPanInt(1), divSym, args[1],
				)
			},
		),
		"//": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				// anything can be divided by nil (and nil works as 1).
				if len(args) < 2 {
					return object.NewTypeErr("// requires at least 2 args")
				}

				// return 1 / args[1]
				return propContainer["Obj_callProp"].(*object.PanBuiltIn).Fn(
					env, object.EmptyPanObjPtr(),
					object.EmptyPanObjPtr(), object.NewPanInt(1), floorDivSym, args[1],
				)
			},
		),
		"_name": object.NewPanStr("Nil"),
		"B": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				if len(args) < 1 {
					return object.NewTypeErr("Nil#B requires at least 1 arg")
				}
				_, ok := object.TraceProtoOfNil(args[0])
				if !ok {
					return object.NewTypeErr(`\1 must be nil`)
				}
				return object.BuiltInFalse
			},
		),
		"new": f(
			func(
				env *object.Env, kwargs *object.PanObj, args ...object.PanObject,
			) object.PanObject {
				if len(args) < 1 {
					return object.NewTypeErr("Nil#bear requires at least 1 arg")
				}

				// NOTE: Nil's descendants also call this
				return object.NewInheritedNil(args[0])
			},
		),
	}
}