org.luaj.vm2
Class LuaNil

java.lang.Object
  org.luaj.vm2.Varargs
      org.luaj.vm2.LuaValue
          org.luaj.vm2.LuaNil

public class LuaNil
extends LuaValue

Class to encapsulate behavior of the singleton instance nil

There will be one instance of this class, LuaValue.NIL, per Java virtual machine. However, the Varargs instance LuaValue.NONE which is the empty list, is also considered treated as a nil value by default.

Although it is possible to test for nil using Java == operator, the recommended approach is to use the method LuaValue.isnil() instead. By using that any ambiguities between LuaValue.NIL and LuaValue.NONE are avoided.

See Also:

LuaValue, LuaValue.NIL

Field Summary

static LuaValue

s_metatable

Fields inherited from class org.luaj.vm2.LuaValue

ADD, CALL, CONCAT, DIV, EMPTYSTRING, EQ, FALSE, INDEX, LE, LEN, LT, METATABLE, MINUSONE, MOD, MODE, MUL, NEWINDEX, NIL, NILS, NONE, NOVALS, ONE, POW, SUB, TBOOLEAN, TFUNCTION, TINT, TLIGHTUSERDATA, TNIL, TNONE, TNUMBER, TOSTRING, TRUE, TSTRING, TTABLE, TTHREAD, TUSERDATA, TVALUE, TYPE_NAMES, UNM, ZERO

Method Summary

LuaValue	checknotnil() Check that this is not the value NIL, or throw LuaError if it is
LuaValue	checkvalidkey() Check that this is a valid key in a table index operation, or throw LuaError if not
boolean	equals(java.lang.Object o)
LuaValue	getmetatable() Get the metatable for this LuaValue
boolean	isnil() Check if this is nil
LuaValue	not() Unary not: return inverse boolean value (~this) as defined by lua not operator
boolean	optboolean(boolean defval) Check that optional argument is a boolean and return its boolean value
LuaClosure	optclosure(LuaClosure defval) Check that optional argument is a closure and return as LuaClosure
double	optdouble(double defval) Check that optional argument is a number or string convertible to number and return as double
LuaFunction	optfunction(LuaFunction defval) Check that optional argument is a function and return as LuaFunction
int	optint(int defval) Check that optional argument is a number or string convertible to number and return as int
LuaInteger	optinteger(LuaInteger defval) Check that optional argument is a number or string convertible to number and return as LuaInteger
java.lang.String	optjstring(java.lang.String defval) Check that optional argument is a string or number and return as Java String
long	optlong(long defval) Check that optional argument is a number or string convertible to number and return as long
LuaNumber	optnumber(LuaNumber defval) Check that optional argument is a number or string convertible to number and return as LuaNumber
LuaString	optstring(LuaString defval) Check that optional argument is a string or number and return as LuaString
LuaTable	opttable(LuaTable defval) Check that optional argument is a table and return as LuaTable
LuaThread	optthread(LuaThread defval) Check that optional argument is a thread and return as LuaThread
java.lang.Object	optuserdata(java.lang.Class c, java.lang.Object defval) Check that optional argument is a userdata whose instance is of a type and return the Object instance
java.lang.Object	optuserdata(java.lang.Object defval) Check that optional argument is a userdata and return the Object instance
LuaValue	optvalue(LuaValue defval) Perform argument check that this is not nil or none.
boolean	toboolean() Convert to boolean false if LuaValue.NIL or FALSE, true if anything else
java.lang.String	tojstring() Convert to human readable String for any type.
int	type() Get the enumeration value for the type of this value.
java.lang.String	typename() Get the String name of the type of this value.

Methods inherited from class org.luaj.vm2.LuaValue

add, add, add, and, arg, arg1, argerror, argerror, aritherror, aritherror, arithmt, arithmtwith, assert_, buffer, call, call, call, call, callmt, checkboolean, checkclosure, checkdouble, checkfunction, checkint, checkinteger, checkjstring, checklong, checkmetatag, checknumber, checknumber, checkstring, checktable, checkthread, checkuserdata, checkuserdata, compareerror, compareerror, comparemt, concat, concat, concatmt, concatTo, concatTo, concatTo, div, div, div, divInto, eq_b, eq, eqmtcall, error, get, get, get, getfenv, getn, gettable, gt_b, gt_b, gt_b, gt, gt, gt, gteq_b, gteq_b, gteq_b, gteq, gteq, gteq, illegal, inext, invoke, invoke, invoke, invoke, invoke, invoke, invokemethod, invokemethod, invokemethod, invokemethod, invokemethod, invokemethod, isboolean, isclosure, isfunction, isint, isinttype, islong, isnumber, isstring, istable, isthread, isuserdata, isuserdata, isweaknil, len, lenerror, length, listOf, listOf, load, lt_b, lt_b, lt_b, lt, lt, lt, lteq_b, lteq_b, lteq_b, lteq, lteq, lteq, metatag, method, method, method, method, method, method, mod, mod, mod, modFrom, mul, mul, mul, narg, neg, neq_b, neq, next, onInvoke, or, pow, pow, pow, powWith, powWith, presize, raweq, raweq, raweq, raweq, raweq, rawget, rawget, rawget, rawset, rawset, rawset, rawset, rawset, rawset, rawset, rawsetlist, set, set, set, set, set, set, set, setfenv, setmetatable, settable, strcmp, strcmp, strongkey, strongvalue, strvalue, sub, sub, sub, subFrom, subFrom, tableOf, tableOf, tableOf, tableOf, tableOf, tableOf, tailcallOf, testfor_b, tobyte, tochar, todouble, tofloat, toint, tolong, tonumber, toshort, tostring, toString, touserdata, touserdata, typerror, unimplemented, userdataOf, userdataOf, valueOf, valueOf, valueOf, valueOf, valueOf, valueOf, varargsOf, varargsOf, varargsOf, varargsOf, varargsOf, varargsOf

Methods inherited from class org.luaj.vm2.Varargs

argcheck, checkboolean, checkclosure, checkdouble, checkfunction, checkint, checkinteger, checkjstring, checklong, checknotnil, checknumber, checkstring, checktable, checkthread, checkuserdata, checkuserdata, checkvalue, eval, isfunction, isnil, isnoneornil, isnumber, isstring, istable, isTailcall, isthread, isuserdata, isvalue, optboolean, optclosure, optdouble, optfunction, optint, optinteger, optjstring, optlong, optnumber, optstring, opttable, optthread, optuserdata, optuserdata, optvalue, subargs, toboolean, tobyte, tochar, todouble, tofloat, toint, tojstring, tolong, toshort, touserdata, touserdata, type

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

s_metatable

public static LuaValue s_metatable

Method Detail

type

public int type()

Description copied from class: LuaValue

Get the enumeration value for the type of this value.

Specified by:

type in class LuaValue

Returns:

value for this type, one of TNIL, TBOOLEAN, TNUMBER, TSTRING, TTABLE, TFUNCTION, TUSERDATA, TTHREAD

See Also:

LuaValue.typename()

typename

public java.lang.String typename()

Description copied from class: LuaValue

Get the String name of the type of this value.

Specified by:

typename in class LuaValue

Returns:

name from type name list LuaValue.TYPE_NAMES corresponding to the type of this value: "nil", "boolean", "number", "string", "table", "function", "userdata", "thread"

See Also:

LuaValue.type()

tojstring

public java.lang.String tojstring()

Description copied from class: LuaValue

Convert to human readable String for any type.

Overrides:

tojstring in class LuaValue

Returns:

String for use by human readers based on type.

See Also:

LuaValue.tostring(), LuaValue.optjstring(String), LuaValue.checkjstring(), LuaValue.isstring(), TSTRING

not

public LuaValue not()

Description copied from class: LuaValue

Unary not: return inverse boolean value (~this) as defined by lua not operator

Overrides:

not in class LuaValue

Returns:

TRUE if NIL or FALSE, otherwise FALSE

toboolean

public boolean toboolean()

Description copied from class: LuaValue

Convert to boolean false if LuaValue.NIL or FALSE, true if anything else

Overrides:

toboolean in class LuaValue

Returns:

Value cast to byte if number or string convertible to number, otherwise 0

See Also:

LuaValue.optboolean(boolean), LuaValue.checkboolean(), LuaValue.isboolean(), TBOOLEAN

isnil

public boolean isnil()

Description copied from class: LuaValue

Check if this is nil

Overrides:

isnil in class LuaValue

Returns:

true if this is nil, otherwise false

See Also:

LuaValue.NIL, LuaValue.NONE, LuaValue.checknotnil(), LuaValue.optvalue(LuaValue), Varargs.isnoneornil(int), LuaValue.TNIL, LuaValue.TNONE

getmetatable

public LuaValue getmetatable()

Description copied from class: LuaValue

Get the metatable for this LuaValue

For LuaTable and LuaUserdata instances, the metatable returned is this instance metatable. For all other types, the class metatable value will be returned.

Overrides:

getmetatable in class LuaValue

Returns:

metatable, or null if it there is none

See Also:

LuaBoolean.s_metatable, LuaNumber.s_metatable, s_metatable, LuaFunction.s_metatable, LuaThread.s_metatable

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class LuaValue

checknotnil

public LuaValue checknotnil()

Description copied from class: LuaValue

Check that this is not the value NIL, or throw LuaError if it is

Overrides:

checknotnil in class LuaValue

Returns:

this if it is not NIL

See Also:

LuaValue.optvalue(LuaValue)

checkvalidkey

public LuaValue checkvalidkey()

Description copied from class: LuaValue

Check that this is a valid key in a table index operation, or throw LuaError if not

Overrides:

checkvalidkey in class LuaValue

Returns:

this if valid as a table key

See Also:

LuaValue.isnil(), LuaValue.isinttype()

optboolean

public boolean optboolean(boolean defval)

Description copied from class: LuaValue

Check that optional argument is a boolean and return its boolean value

Overrides:

optboolean in class LuaValue

Parameters:

defval - boolean value to return if this is nil or none

Returns:

this cast to boolean if a , defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.checkboolean(), LuaValue.isboolean(), LuaValue.TBOOLEAN

optclosure

public LuaClosure optclosure(LuaClosure defval)

Description copied from class: LuaValue

Check that optional argument is a closure and return as LuaClosure

A LuaClosure is a that executes lua byteccode.

Overrides:

optclosure in class LuaValue

Parameters:

defval - LuaClosure to return if this is nil or none

Returns:

this cast to LuaClosure if a function, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.checkclosure(), LuaValue.isclosure(), LuaValue.TFUNCTION

optdouble

public double optdouble(double defval)

Description copied from class: LuaValue

Check that optional argument is a number or string convertible to number and return as double

Overrides:

optdouble in class LuaValue

Parameters:

defval - double to return if this is nil or none

Returns:

this cast to double if numeric, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.optint(int), LuaValue.optinteger(LuaInteger), LuaValue.checkdouble(), LuaValue.todouble(), LuaValue.tonumber(), LuaValue.isnumber(), LuaValue.TNUMBER

optfunction

public LuaFunction optfunction(LuaFunction defval)

Description copied from class: LuaValue

Check that optional argument is a function and return as LuaFunction

A LuaFunction may either be a Java function that implements functionality directly in Java, or a LuaClosure which is a LuaFunction that executes lua bytecode.

Overrides:

optfunction in class LuaValue

Parameters:

defval - LuaFunction to return if this is nil or none

Returns:

this cast to LuaFunction if a function, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.checkfunction(), LuaValue.isfunction(), LuaValue.TFUNCTION

optint

public int optint(int defval)

Description copied from class: LuaValue

Check that optional argument is a number or string convertible to number and return as int

Overrides:

optint in class LuaValue

Parameters:

defval - int to return if this is nil or none

Returns:

this cast to int if numeric, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.optdouble(double), LuaValue.optlong(long), LuaValue.optinteger(LuaInteger), LuaValue.checkint(), LuaValue.toint(), LuaValue.tonumber(), LuaValue.isnumber(), LuaValue.TNUMBER

optinteger

public LuaInteger optinteger(LuaInteger defval)

Description copied from class: LuaValue

Check that optional argument is a number or string convertible to number and return as LuaInteger

Overrides:

optinteger in class LuaValue

Parameters:

defval - LuaInteger to return if this is nil or none

Returns:

this converted and wrapped in LuaInteger if numeric, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.optdouble(double), LuaValue.optint(int), LuaValue.checkint(), LuaValue.toint(), LuaValue.tonumber(), LuaValue.isnumber(), LuaValue.TNUMBER

optlong

public long optlong(long defval)

Description copied from class: LuaValue

Check that optional argument is a number or string convertible to number and return as long

Overrides:

optlong in class LuaValue

Parameters:

defval - long to return if this is nil or none

Returns:

this cast to long if numeric, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.optdouble(double), LuaValue.optint(int), LuaValue.checkint(), LuaValue.toint(), LuaValue.tonumber(), LuaValue.isnumber(), LuaValue.TNUMBER

optnumber

public LuaNumber optnumber(LuaNumber defval)

Description copied from class: LuaValue

Check that optional argument is a number or string convertible to number and return as LuaNumber

Overrides:

optnumber in class LuaValue

Parameters:

defval - LuaNumber to return if this is nil or none

Returns:

this cast to LuaNumber if numeric, defval if nil or none, throws LuaError otherwise

See Also:

LuaValue.optdouble(double), LuaValue.optlong(long), LuaValue.optint(int), LuaValue.checkint(), LuaValue.toint(), LuaValue.tonumber(), LuaValue.isnumber(), LuaValue.TNUMBER

opttable

public LuaTable opttable(LuaTable defval)

Description copied from class: LuaValue

Check that optional argument is a table and return as LuaTable

Overrides:

opttable in class LuaValue

Parameters:

defval - LuaTable to return if this is nil or none

Returns:

this cast to LuaTable if a table, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.checktable(), LuaValue.istable(), LuaValue.TTABLE

optthread

public LuaThread optthread(LuaThread defval)

Description copied from class: LuaValue

Check that optional argument is a thread and return as LuaThread

Overrides:

optthread in class LuaValue

Parameters:

defval - LuaThread to return if this is nil or none

Returns:

this cast to LuaTable if a thread, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.checkthread(), LuaValue.isthread(), LuaValue.TTHREAD

optjstring

public java.lang.String optjstring(java.lang.String defval)

Description copied from class: LuaValue

Check that optional argument is a string or number and return as Java String

Overrides:

optjstring in class LuaValue

Parameters:

defval - LuaString to return if this is nil or none

Returns:

this converted to String if a string or number, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.tojstring(), LuaValue.optstring(LuaString), LuaValue.checkjstring(), LuaValue.toString(), LuaValue.TSTRING

optstring

public LuaString optstring(LuaString defval)

Description copied from class: LuaValue

Check that optional argument is a string or number and return as LuaString

Overrides:

optstring in class LuaValue

Parameters:

defval - LuaString to return if this is nil or none

Returns:

this converted to LuaString if a string or number, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.tojstring(), LuaValue.optjstring(String), LuaValue.checkstring(), LuaValue.toString(), LuaValue.TSTRING

optuserdata

public java.lang.Object optuserdata(java.lang.Object defval)

Description copied from class: LuaValue

Check that optional argument is a userdata and return the Object instance

Overrides:

optuserdata in class LuaValue

Parameters:

defval - Object to return if this is nil or none

Returns:

Object instance of the userdata if a LuaUserdata, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.checkuserdata(), LuaValue.isuserdata(), LuaValue.optuserdata(Class, Object), LuaValue.TUSERDATA

optuserdata

public java.lang.Object optuserdata(java.lang.Class c,
                                    java.lang.Object defval)

Description copied from class: LuaValue

Check that optional argument is a userdata whose instance is of a type and return the Object instance

Overrides:

optuserdata in class LuaValue

Parameters:

c - Class to test userdata instance against

defval - Object to return if this is nil or none

Returns:

Object instance of the userdata if a LuaUserdata and instance is assignable to c, defval if nil or none, throws LuaError if some other type

See Also:

LuaValue.checkuserdata(Class), LuaValue.isuserdata(Class), LuaValue.optuserdata(Object), LuaValue.TUSERDATA

optvalue

public LuaValue optvalue(LuaValue defval)

Description copied from class: LuaValue

Perform argument check that this is not nil or none.

Overrides:

optvalue in class LuaValue

Parameters:

defval - LuaValue to return if this is nil or none

Returns:

this if not nil or none, else defval

See Also:

LuaValue.NIL, LuaValue.NONE, LuaValue.isnil(), Varargs.isnoneornil(int), LuaValue.TNIL, LuaValue.TNONE