Qore Programming Language Reference Manual  0.8.12.9
<nothing> Class Reference

Methods in this pseudo-class can be executed on NOTHING. More...

Inheritance diagram for Qore::<nothing>:

Public Member Functions

SingleValueIterator contextIterator ()
 Returns an empty SingleValueIterator object. More...
 
nothing firstKey ()
 Returns NOTHING. More...
 
nothing firstValue ()
 Returns NOTHING. More...
 
bool hasKey (softstring key)
 Returns True if the key exists in the hash (may or may not be assigned a value), False if not. More...
 
bool hasKeyValue (softstring key)
 Returns True if the key exists and is assigned to a value, False if not. More...
 
SingleValueIterator keyIterator ()
 Returns an empty SingleValueIterator object. More...
 
list keys ()
 Returns an empty list. More...
 
nothing lastKey ()
 Returns NOTHING. More...
 
nothing lastValue ()
 Returns NOTHING. More...
 
int lsize ()
 Returns 0. More...
 
SingleValueIterator pairIterator ()
 Returns an empty SingleValueIterator object. More...
 
SingleValueIterator rangeIterator ()
 Returns an empty SingleValueIterator object. More...
 
int typeCode ()
 Returns Qore::NT_NOTHING. More...
 
list values ()
 Returns an empty list. More...
 
- Public Member Functions inherited from <value>
bool callp ()
 Returns False; this method is reimplemented in other types and will return True if the given expression is a callable value (ie closures or call references) More...
 
bool empty ()
 Returns True; this method will be reimplemented in container types where it may return False. More...
 
bool intp ()
 Returns False; this method is reimplemented in other types and will return True if the given expression can be converted to an integer. More...
 
AbstractIterator iterator ()
 Returns an iterator object for the value; the default iterator object returned is SingleValueIterator. More...
 
int lsize ()
 Returns 1; the return value of this method should give the list size of the value, which is normally 1 for non-lists (except for NOTHING where the size will be 0) and the number of the elements in the list for lists; this method will be reimplemented in other types where it may return other values. More...
 
int size ()
 Returns zero; this method will be reimplemented in container types where it may return a non-zero value. More...
 
bool sizep ()
 Returns True if the type can return a non-zero size (True for containers including binary objects and strings, False for everything else) More...
 
bool strp ()
 Returns False; this method is reimplemented in other types and will return True if the given expression can be converted to a string. More...
 
bool toBool ()
 Returns the boolean representation of the value; the default is False. More...
 
float toFloat ()
 Returns the floating-point representation of the value; the default is 0.0. More...
 
int toInt ()
 Returns the integer representation of the value; the default is 0. More...
 
number toNumber ()
 Returns the arbitrary-precision numeric representation of the value; the default is 0. More...
 
string toString ()
 Returns the string representation of the value; the default is an empty string. More...
 
string type ()
 Returns the string type for the value. More...
 
int typeCode ()
 Returns the type code for the value. More...
 
bool val ()
 Returns False; this method is reimplemented in other types and will return True if the given expression has a value that would be converted to True according to the rules described in %perl-bool-eval. More...
 

Detailed Description

Methods in this pseudo-class can be executed on NOTHING.

Member Function Documentation

◆ contextIterator()

SingleValueIterator <nothing>::contextIterator ( )

Returns an empty SingleValueIterator object.

Returns
an empty SingleValueIterator object
Code Flags:
CONSTANT
Example:
map printf("+ %y\n", $1), get_hash_or_nothing().contextIterator();
See also
<hash>::contextIterator()
Since
Qore 0.8.6.2

◆ firstKey()

nothing <nothing>::firstKey ( )

Returns NOTHING.

Returns
NOTHING
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
*string n = h.firstKey();
See also
<hash>::firstKey()
Since
Qore 0.8.7

◆ firstValue()

nothing <nothing>::firstValue ( )

Returns NOTHING.

Returns
NOTHING
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
any n = h.firstValue();
See also
<hash>::firstValue()
Since
Qore 0.8.7

◆ hasKey()

bool <nothing>::hasKey ( softstring  key)

Returns True if the key exists in the hash (may or may not be assigned a value), False if not.

Code Flags:
CONSTANT
Parameters
keythe key name to check
Returns
True if the key exists in the hash (may or may not be assigned a value), False if not
Example:
*hash h = hash_or_nothing();
bool b = h.hasKey(key);
See also
<hash>::hasKey(softstring)
Since
Qore 0.8.7

◆ hasKeyValue()

bool <nothing>::hasKeyValue ( softstring  key)

Returns True if the key exists and is assigned to a value, False if not.

Code Flags:
CONSTANT
Parameters
keythe key name to check
Returns
True if the key exists and is assigned to a value, False if not
Example:
*hash h = hash_or_nothing();
bool b = h.hasKeyValue(key);
See also
<hash>::hasKeyValue(softstring)
Since
Qore 0.8.7

◆ keyIterator()

SingleValueIterator <nothing>::keyIterator ( )

Returns an empty SingleValueIterator object.

Returns
an empty SingleValueIterator object
Code Flags:
CONSTANT
Example:
map printf("+ %y\n", $1), get_hash_or_nothing().keyIterator();
See also
<hash>::keyIterator()
Since
Qore 0.8.6.2

◆ keys()

list <nothing>::keys ( )

Returns an empty list.

Returns
an empty list
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
list l = h.keys();
See also
<hash>::keys()
Since
Qore 0.8.7

◆ lastKey()

nothing <nothing>::lastKey ( )

Returns NOTHING.

Returns
NOTHING
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
*string n = h.firstKey();
See also
<hash>::firstKey()
Since
Qore 0.8.7

◆ lastValue()

nothing <nothing>::lastValue ( )

Returns NOTHING.

Returns
NOTHING
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
any n = h.firstValue();
See also
<hash>::lastValue()
Since
Qore 0.8.7

◆ lsize()

int <nothing>::lsize ( )

Returns 0.

Returns
0
Code Flags:
CONSTANT
Example:
printf("iterating %d element%s\n", val.lsize(), val.lsize() == 1 ? "" : "s");
foreach any element in (val) {
do_something(element);
}

◆ pairIterator()

SingleValueIterator <nothing>::pairIterator ( )

Returns an empty SingleValueIterator object.

Returns
an empty SingleValueIterator object
Code Flags:
CONSTANT
Example:
map printf("+ %y\n", $1), get_hash_or_nothing().pairIterator();
Since
Qore 0.8.6.2

◆ rangeIterator()

SingleValueIterator <nothing>::rangeIterator ( )

Returns an empty SingleValueIterator object.

Returns
an empty SingleValueIterator object
Code Flags:
CONSTANT
Example:
map printf("+ %y\n", $1), get_list_or_nothing().rangeIterator();
See also
<list>::rangeIterator()
Since
Qore 0.8.8

◆ typeCode()

int <nothing>::typeCode ( )

Returns Qore::NT_NOTHING.

Returns
Qore::NT_NOTHING
Code Flags:
CONSTANT
Example:
switch (n.typeCode()) {
case NT_NOTHING:
printf("%y: no value\n", n);
break;
}

◆ values()

list <nothing>::values ( )

Returns an empty list.

Returns
an empty list
Code Flags:
CONSTANT
Example:
*hash h = hash_or_nothing();
list l = h.values();
See also
<hash>::values()
Since
Qore 0.8.7