8. LFUN
Namespace lfun::
- Description
Callback functions used to overload various builtin functions.
The functions can be grouped into a few sets:
Object initialization and destruction.
__INIT()
,create()
,destroy()
Unary operator overloading.
`~()
,`!()
,_values()
,cast()
,_sizeof()
,_indices()
,__hash()
Binary asymmetric operator overloading.
`+()
,``+()
,`-()
,``-()
,`&()
,``&()
,`|()
,``|()
,`^()
,``^()
,`<<()
,``<<()
,`>>()
,``>>()
,`*()
,``*()
,`/()
,``/()
,`%()
,``%()
Binary symmetric operator overloading.
The optimizer will make assumptions about the relations between these functions.
`==()
,_equal()
,`<()
,`>()
Other binary operator overloading.
`[]()
,`[]=()
,`->()
,`->=()
,`+=()
,`()()
Overloading of other builtin functions.
_is_type()
,_sprintf()
,_m_delete()
,_get_iterator()
,_search()
- Note
Although these functions are called from outside the object they exist in, they will still be used even if they are declared
protected
. It is in fact recommended to declare themprotected
, since that will hinder them being used for other purposes.- See also
::
- Method__INIT
void
__INIT()- Description
Inherit and variable initialization.
This function is generated automatically by the compiler. It's called just before
lfun::create()
when an object is instantiated.It first calls any
__INIT
functions in inherited classes (regardless of modifiers on the inherits). It then executes all the variable initialization expressions in this class, in the order they occur.- Note
This function can not be overloaded or blocked from executing.
- See also
lfun::create()
- Method__hash
int
__hash()- Description
Hashing callback.
The main caller of this function is
predef::hash_value()
or the low-level equivalent, which get called by various mapping operations when the object is used as index in a mapping.- Returns
It should return an integer that corresponds to the object in such a way that all values which
lfun::`==
considers equal to the object get the same hash value.- Note
The function
predef::hash
does not return hash values that are compatible with this one.- Note
It's assumed that this function is side-effect free.
- See also
lfun::`==
,predef::hash_value()
- Method_deserialize
void
_deserialize(object
o
,function
(function
(mixed
:void
),string
,type
:mixed
)deserializer
)- Description
Dispatch function for
Serialization.deserialize()
.- Parameter
o
Object to serialize. Always a context of the current object.
- Parameter
deserializer
Function to be called once for every variable to serialize.
The
deserializer
function expects to be called with three arguments:setter - Function that sets the symbol value.
symbol - The symbol name.
symbol_type - The type of the symbol.
- Note
A default implementation of
lfun::_serialize()
andlfun::_deserialize()
is available inSerializer.Serializable
.- See also
lfun::_serialize()
,Serializer.deserialize()
,Serializer.Serializable()->_deserialize()
- Method_equal
int
_equal(mixed
arg
)- Description
Recursive equality callback.
- Note
It's assumed that this function is side-effect free.
- See also
predef::equal()
,lfun::`==()
- Method_get_iterator
predef::Iterator
_get_iterator()- Description
Iterator creation callback.
The returned
predef::Iterator
instance works as a cursor that references a specific item contained (in some arbitrary sense) in this one.- Note
It's assumed that this function is side-effect free.
- See also
predef::Iterator
,predef::get_iterator
,predef::foreach()
- Method_indices
array
_indices(object
|void
context
,int
|void
access
)- Description
List indices callback.
- Returns
Expected to return an array with the valid indices in the object.
- Note
It's assumed that this function is side-effect free.
- See also
predef::indices()
,lfun::_values()
,lfun::_types()
,::_indices()
- Method_is_type
bool
_is_type(string
basic_type
)- Description
Type comparison callback.
Called by the cast operator to determine if an object simulates a basic type.
- Parameter
basic_type
One of:
"array"
"float"
"function"
"int"
"mapping"
"multiset"
"object"
"program"
"string"
"type"
"void"
"zero"
The following five shouldn't occurr, but are here for completeness:
"lvalue"
"mapping_data"
"object storage"
"pike_frame"
"unknown"
- Returns
Expected to return
1
if the object is to be regarded as a simulation of the type specified bybasic_type
.- Note
The argument is currently a string with the name of the type, but might in the future be a value of the type type.
- Note
It's assumed that this function is side-effect free.
- Method_m_delete
mixed
_m_delete(mixed
arg
)- Description
Delete index callback.
- See also
predef::m_delete()
- Method_random
mixed
_random()- Description
Called by
random()
. Typical use is when the object implements a ADT, when a call to this lfun should return a random member of the ADT or range implied by the ADT.- See also
predef::random()
- Method_search
mixed
_search(mixed
needle
,mixed
|void
start
)- Description
Search callback.
- See also
predef::search()
- Method_serialize
void
_serialize(object
o
,function
(mixed
,string
,type
:void
)serializer
)- Description
Dispatch function for
Serializer.serialize()
.- Parameter
o
Object to serialize. Always a context of the current object.
- Parameter
serializer
Function to be called once for every variable to serialize.
The
serializer
function expects to be called with three arguments:value - The value of the symbol.
symbol - The symbol name.
symbol_type - The type of the symbol.
- Note
A default implementation of
lfun::_serialize()
andlfun::_deserialize()
is available inSerializer.Serializable
.- See also
lfun::_deserialize()
,Serializer.serialize()
,Serializer.Serializable()->_serialize()
- Method_size_object
int
_size_object()- Description
Debug.size_object()
callback.- Returns
Returns an approximation of the memory use in bytes for the object.
- See also
Debug.size_object()
,lfun::_sizeof()
- Method_sizeof
int
_sizeof()- Description
Size query callback.
Called by
predef::sizeof()
to determine the number of elements in an object. If this function is not present, the number of public symbols in the object will be returned.- Returns
Expected to return the number of valid indices in the object.
- Note
It's assumed that this function is side-effect free.
- See also
predef::sizeof()
- Method_sprintf
string
_sprintf(int
conversion_type
,mapping
(string
:int
)|void
params
)- Description
Sprintf callback.
This method is called by
predef::sprintf()
to print objects. If it is not present, printing of the object will not be supported for any conversion-type except for the %O-conversion-type, which will output"object"
.- Parameter
conversion_type
One of:
'b'
Signed binary integer.
'd'
Signed decimal integer.
'u'
Unsigned decimal integer.
'o'
Signed octal integer.
'x'
Lowercase signed hexadecimal integer.
'X'
Uppercase signed hexadecimal integer.
'c'
Character. If a fieldsize has been specified this will output the low-order bytes of the integer in network byte order.
'f'
Float.
'g'
Heuristically chosen representation of float.
'G'
Like %g, but uses uppercase E for exponent.
'e'
Exponential notation float.
'E'
Like %e, but uses uppercase E for exponent.
's'
String.
'O'
Any value (debug style).
't'
Type of the argument.
- Parameter
params
Conversion parameters. The following parameters may be supplied:
"precision"
:int
Precision.
"width"
:int
Field width.
"flag_left"
:int(1..1)
Indicates that the output should be left-aligned.
"indent"
:int
Indentation level in %O-mode.
- Returns
Is expected to return a string describing the object formatted according to
conversion_type
.- Note
_sprintf()
is currently not called for the following conversion-types:'F'
Binary IEEE representation of float (%4F gives single precision, %8F gives double precision.)
- Note
This function might be called at odd times, e.g. before
lfun::create
has been called or when an error has occurred. The reason is typically that it gets called when a backtrace is being formatted to report an error. It should therefore be very robust and not make any assumptions about its own internal state, at least not whenconversion_type
is'O'
.- Note
It's assumed that this function is side-effect free.
- See also
predef::sprintf()
- Method_sqrt
mixed
_sqrt()- Description
Called by sqrt when the square root of an object is requested.
- Note
_sqrt is not a real lfun, so it must not be defined as static.
- See also
predef::sqrt()
- Method_types
array
_types(object
|void
context
,int
|void
access
)- Description
List types callback.
This callback is typically called via
predef::types()
.- Returns
Expected to return an array with the types corresponding to the indices returned by
lfun::_indices()
.- Note
It's assumed that this function is side-effect free.
- Note
predef::types()
was added in Pike 7.9.- See also
predef::types()
,lfun::_indices()
,lfun::_values()
,::_types()
- Method_values
array
_values(object
|void
context
,int
|void
access
)- Description
List values callback.
- Returns
Expected to return an array with the values corresponding to the indices returned by
lfun::_indices()
.- Note
It's assumed that this function is side-effect free.
- See also
predef::values()
,lfun::_indices()
,lfun::_types()
,::_values()
- Method`!
int
`!()- Description
Logical not callback.
- Returns
Returns non-zero if the object should be evaluated as false, and
0
(zero) otherwise.- Note
It's assumed that this function is side-effect free.
- See also
predef::`!()
- Method`%
mixed
`%(zero
...args
)- Description
Left side modulo callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``%()
,predef::`%()
- Method`&
mixed
`&(zero
...args
)- Description
Left side bitwise and/intersection callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``&()
,predef::`&()
- Method`()
mixed
`()(zero
...args
)- Description
Apply callback.
- See also
predef::`()
- Method`*
mixed
`*(zero
...args
)- Description
Left side multiplication/repetition/implosion callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``*()
,predef::`*()
- Method`+
mixed
`+(zero
arg
,zero
...rest
)- Description
Left side addition/concatenation callback.
This is used by
predef::`+
. It's called with any arguments that follow this object in the argument list of the call topredef::`+
. The returned value should be a new instance that represents the addition/concatenation between this object and the arguments in the order they are given.- Note
It's assumed that this function is side-effect free.
- See also
lfun::``+()
,lfun::`+=()
,predef::`+()
- Method`+=
this_program
`+=(zero
arg
,zero
...rest
)- Description
Destructive addition/concatenation callback.
This is used by
predef::`+
. It's called with any arguments that follow this object in the argument list of the call topredef::`+
. It should update this object to represent the addition/concatenation between it and the arguments in the order they are given. It should always return this object.- Note
This function should only be implemented if
lfun::`+()
also is. It should only work as a more optimized alternative to that one, for the case when it's safe to change the object destructively and use it directly as the result.- Note
This function is not an lfun for the
+=
operator. It's only whether or not it's safe to do a destructive change that decides if this function orlfun::`+()
is called; both the+
operator and the+=
operator can call either one.- See also
lfun::`+()
,predef::`+()
- Method`-
mixed
`-(void
|zero
arg
)- Description
Negation and left side subtraction/set difference callback.
This is used by
predef::`-
. When called without an argument the result should be a new instance that represents the negation of this object, otherwise the result should be a new instance that represents the difference between this object andarg
.- Note
It's assumed that this function is side-effect free.
- See also
lfun::``-()
,predef::`-()
- Method`->
mixed
`->(string
index
,object
|void
context
,int
|void
access
)- Description
Arrow index callback.
- Parameter
index
Symbol in
context
to access.- Parameter
context
Context in the current object to start the search from. If
UNDEFINED
or left out,this_program::this
is to be be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
- Returns
Returns the value at
index
if it exists, andUNDEFINED
otherwise.- Note
It's assumed that this function is side-effect free.
- See also
predef::`->()
,::`->()
- Method`->=
mixed
`->=(string
index
,zero
value
,object
|void
context
,int
|void
access
)- Description
Arrow index assignment callback.
- Parameter
index
Symbol in
context
to change the value of.- Parameter
value
The new value.
- Parameter
context
Context in the current object to start the search from. If
UNDEFINED
or left out,this_program::this
is to be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
This function is to index the current object with the string
index
, and set it tovalue
.- Returns
Returns the set
value
.- See also
predef::`->=()
,::`->=()
,lfun::`[]=()
- Method`/
mixed
`/(zero
...args
)- Description
Left side division/split callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``/()
,predef::`/()
- Method`<
bool
`<(mixed
arg
)- Description
Less than test callback.
- Note
It's assumed that this function is side-effect free.
- See also
predef::`<()
- Method`<<
mixed
`<<(zero
arg
)- Description
Left side left shift callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``<<()
,predef::`<<()
- Method`==
bool
`==(mixed
arg
)- Description
Equality test callback.
- Note
If this is implemented it might be necessary to implement
lfun::__hash
too. Otherwise mappings might hold several objects as indices which are duplicates according to this function. Various other functions that use hashing also might not work correctly, e.g.predef::Array.uniq
.- Note
It's assumed that this function is side-effect free.
- See also
predef::`==()
,lfun::__hash
- Method`>
bool
`>(mixed
arg
)- Description
Greater than test callback.
- Note
It's assumed that this function is side-effect free.
- See also
predef::`>()
- Method`>>
mixed
`>>(zero
arg
)- Description
Left side right shift callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``>>()
,predef::`>>()
- Method`[..]
mixed
`[..](zero
low
,int
low_bound_type
,zero
high
,int
high_bound_type
)- Description
Subrange callback.
- Note
It's assumed that this function is side-effect free.
- See also
predef::`[..]
- Method`[]
mixed
`[](zero
arg1
,zero
|void
arg2
)- Description
Indexing callback.
For compatibility, this is also called to do subranges unless there is a
`[..]
in the class. Seepredef::`[..]
for details.- Note
It's assumed that this function is side-effect free.
- See also
predef::`[]()
,predef::`[..]
- Method`[]=
mixed
`[]=(zero
arg1
,zero
arg2
)- Description
Index assignment callback.
- See also
predef::`[]=()
,lfun::`->=()
- Method`^
mixed
`^(zero
...args
)- Description
Left side exclusive or callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``^()
,predef::`^()
- Method``%
mixed
``%(zero
...args
)- Description
Right side modulo callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`%()
,predef::`%()
- Method``&
mixed
``&(zero
...args
)- Description
Right side bitwise and/intersection callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`&()
,predef::`&()
- Method``*
mixed
``*(zero
...args
)- Description
Right side multiplication/repetition/implosion callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`*()
,predef::`*()
- Method``+
mixed
``+(zero
arg
,zero
...rest
)- Description
Right side addition/concatenation callback.
This is used by
predef::`+
. It's called with any arguments that precede this object in the argument list of the call topredef::`+
. The returned value should be a new instance that represents the addition/concatenation between the arguments in the order they are given and this object.- Note
It's assumed that this function is side-effect free.
- See also
lfun::`+()
,predef::`+()
- Method``-
mixed
``-(zero
arg
)- Description
Right side subtraction/set difference callback.
This is used by
predef::`-
. The result should be a new instance that represents the difference betweenarg
and this object.- Note
It's assumed that this function is side-effect free.
- See also
lfun::`-()
,predef::`-()
- Method``/
mixed
``/(zero
...args
)- Description
Right side division/split callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`/()
,predef::`/()
- Method``<<
mixed
``<<(zero
arg
)- Description
Right side left shift callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`<<()
,predef::`<<()
- Method``>>
mixed
``>>(zero
arg
)- Description
Right side right shift callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`>>()
,predef::`>>()
- Method``^
mixed
``^(zero
...args
)- Description
Right side exclusive or callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`^()
,predef::`^()
- Method``|
mixed
``|(zero
...args
)- Description
Right side bitwise or/union callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::`|()
,predef::`|()
- Method`|
mixed
`|(zero
...args
)- Description
Left side bitwise or/union callback.
- Note
It's assumed that this function is side-effect free.
- See also
lfun::``|()
,predef::`|()
- Method`~
mixed
`~()- Description
Complement/inversion callback.
- Note
It's assumed that this function is side-effect free.
- See also
predef::`~()
- Methodcast
mixed
cast(string
requested_type
)- Description
Value cast callback.
- Parameter
requested_type
Type to cast to.
- Returns
Expected to return the object value-casted (converted) to the type described by
requested_type
.- Note
The argument is currently a string with the name of the type, but might in the future be a value of the type type.
- Note
Currently casting between object types is a noop.
- Note
If the returned value is not deemed to be of the requested type a runtime error may be thrown.
- Note
It's assumed that this function is side-effect free.
- Methodcreate
void
lfun:create(zero
...args
)- Description
Object creation callback.
This function is called right after
lfun::__INIT()
.args
are the arguments passed when the program was called.- Note
In Pike 7.2 and later this function can be created implicitly by the compiler using the new syntax:
<span class='type'>class</span> Foo<span class='delim'>(</span><span class='type'>int</span> foo<span class='delim'>)</span> <span class='delim'>{</span> <span class='type'>int</span> bar<span class='delim'>;</span> <span class='delim'>}</span>
In the above case an implicit
lfun::create()
is created, and it's equivalent to:<span class='type'>class</span> Foo <span class='delim'>{</span> <span class='type'>int</span> foo<span class='delim'>;</span> <span class='type'>int</span> bar<span class='delim'>;</span> <span class='mod'>protected</span> <span class='type'>void</span> create<span class='delim'>(</span><span class='type'>int</span> foo<span class='delim'>)</span> <span class='delim'>{</span> <span class='mod'>local</span>::foo <span class='delim'>=</span> foo<span class='delim'>;</span> <span class='delim'>}</span> <span class='delim'>}</span>
- See also
lfun::__INIT()
,lfun::destroy()
- Methoddestroy
void
destroy(void
|int
reason
)- Description
Object destruction callback.
This function is called right before the object is destructed. That can happen either through a call to
predef::destruct()
, when there are no more references to the object, or when the garbage collector discovers that it's part of a cyclic data structure that has become garbage.- Parameter
reason
A flag that tells why the object is destructed:
Object.DESTRUCT_EXPLICIT
Destructed explicitly by
predef::destruct
.Object.DESTRUCT_NO_REFS
Destructed due to running out of references.
Object.DESTRUCT_GC
Destructed by the garbage collector.
Object.DESTRUCT_CLEANUP
Destructed as part of the cleanup when the pike process exits. Occurs only if Pike has been compiled with the configure option --with-cleanup-on-exit. See note below.
- Note
Objects are normally not destructed when a process exits, so
destroy
functions aren't called then. Useatexit
to get called when the process exits.- Note
Regarding destruction order during garbage collection:
If an object is destructed by the garbage collector, it's part of a reference cycle with other things but with no external references. If there are other objects with
destroy
functions in the same cycle, it becomes a problem which to call first.E.g. if this object has a variable with another object which (directly or indirectly) points back to this one, you might find that the other object already has been destructed and the variable thus contains zero.
The garbage collector tries to minimize such problems by defining an order as far as possible:
If an object A contains an
lfun::destroy
and an object B does not, then A is destructed before B.If A references B single way, then A is destructed before B.
If A and B are in a cycle, and there is a reference somewhere from B to A that is weaker than any reference from A to B, then A is destructed before B.
If a cycle is resolved according to the rule above by ignoring a weaker reference, and there is another ambiguous cycle that would get resolved by ignoring the same reference, then the latter cycle will be resolved by ignoring that reference.
Weak references (e.g. set with
predef::set_weak_flag()
) are considered weaker than normal references, and both are considered weaker than strong references.Strong references are those from objects to the objects of their lexically surrounding classes. There can never be a cycle consisting only of strong references. (This means the gc never destructs a parent object before all children have been destructed.)
An example with well defined destruct order due to strong references:
<span class='type'>class</span> Super <span class='delim'>{</span> <span class='type'>class</span> Sub <span class='delim'>{</span> <span class='mod'>protected</span> <span class='type'>void</span> destroy<span class='delim'>(</span><span class='delim'>)</span> <span class='delim'>{</span> <span class='lang'>if</span> <span class='delim'>(</span><span class='delim'>!</span>Super::<span class='const'>this</span><span class='delim'>)</span> error <span class='delim'>(</span><span class='string'>"My parent has been destructed!\n"</span><span class='delim'>)</span><span class='delim'>;</span> <span class='delim'>}</span> <span class='delim'>}</span> Sub sub <span class='delim'>=</span> Sub<span class='delim'>(</span><span class='delim'>)</span><span class='delim'>;</span> <span class='mod'>protected</span> <span class='type'>void</span> destroy<span class='delim'>(</span><span class='delim'>)</span> <span class='delim'>{</span> <span class='lang'>if</span> <span class='delim'>(</span><span class='delim'>!</span>sub<span class='delim'>)</span> werror <span class='delim'>(</span><span class='string'>"sub already destructed.\n"</span><span class='delim'>)</span><span class='delim'>;</span> <span class='delim'>}</span> <span class='delim'>}</span>
The garbage collector ensures that these objects are destructed in an order so that
werror
inSuper
is called and noterror
inSub
.- Note
When the garbage collector calls
lfun::destroy
, all accessible non-objects and objects withoutdestroy
functions are still intact. They are not freed if thedestroy
function adds external references to them. However, all objects withlfun::destroy
in the cycle are already scheduled for destruction and will therefore be destroyed even if external references are added to them.- Note
The garbage collector had completely random destruct order in versions prior to 7.2.
- See also
lfun::create()
,predef::destruct()
- Variablesymbol
mixed
lfun::symbol
Namespace ::
- Description
Symbols implicitly inherited from the virtual base class.
These symbols exist mainly to simplify implementation of the corresponding lfuns.
- See also
lfun::
- Method_indices
mixed
_indices(object
|void
context
,int
|void
access
)- Parameter
context
Context in the current object to start the list from. If
UNDEFINED
or left out, this_program::this will be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
Builtin function to list the identifiers of an object. This is useful when
lfun::_indices
has been overloaded.- See also
::_values()
,::_types()
,::`->()
- Method_types
mixed
_types(object
|void
context
,int
|void
access
)- Parameter
context
Context in the current object to start the list from. If
UNDEFINED
or left out, this_program::this will be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
Builtin function to list the types of the identifiers of an object. This is useful when
lfun::_types
has been overloaded.- See also
::_indices()
,::_values()
,::`->()
- Method_values
mixed
_values(object
|void
context
,int
|void
access
)- Parameter
context
Context in the current object to start the list from. If
UNDEFINED
or left out, this_program::this will be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
Builtin function to list the values of the identifiers of an object. This is useful when
lfun::_values
has been overloaded.- See also
::_indices()
,::_types()
,::`->()
- Method`->
mixed
`->(string
index
,object
|void
context
,int
|void
access
)- Description
Builtin arrow operator.
- Parameter
index
Symbol in
context
to access.- Parameter
context
Context in the current object to start the search from. If
UNDEFINED
or left out,this_program::this
will be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
This function indexes the current object with the string
index
. This is useful when the arrow operator has been overloaded.- See also
::`->=()
- Method`->=
void
`->=(string
index
,mixed
value
,object
|void
context
,int
|void
access
)- Description
Builtin arrow set operator.
- Parameter
index
Symbol in
context
to change the value of.- Parameter
value
The new value.
- Parameter
context
Context in the current object to start the search from. If
UNDEFINED
or left out,this_program::this
will be used (ie start at the current context and ignore any overloaded symbols).- Parameter
access
Access permission override. One of the following:
0
See only public symbols.
UNDEFINED
1
See protected symbols as well.
This function indexes the current object with the string
index
, and sets it tovalue
. This is useful when the arrow set operator has been overloaded.- See also
::`->()