C++

Reference

<functional>

header

<functional>

Function objects
Function objects are objects specifically designed to be used with a syntax similar to that of functions. In C++, this is achieved by defining member function operator() in their class, like for example:
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struct myclass {
  int operator()(int a) {return a;}
} myobject;
int x = myobject (0);           // function-like syntax with object myobject

They are typically used as arguments to functions, such as predicates or comparison functions passed to standard algorithms.

Base classes

unary_function
Unary function object base class (class template)
binary_function
Binary function object base class (class template)

Operator classes

Arithmetic operations:
plus
Addition function object class (class template)
minus
Subtraction function object class (class template)
multiplies
Multiplication function object class (class template)
divides
Division function object class (class template)
modulus
Modulus function object class (class template)
negate
Negative function object class (class template)

Comparison operations:
equal_to
Function object class for equality comparison (class template)
not_equal_to
Function object class for non-equality comparison (class template)
greater
Function object class for greater-than inequality comparison (class template)
less
Function object class for less-than inequality comparison (class template)
greater_equal
Function object class for greater-than-or-equal-to comparison (class template)
less_equal
Function object class for less-than-or-equal-to comparison (class template)

Logical operations:
logical_and
Logical AND function object class (class template)
logical_or
Logical OR function object class (class template)
logical_not
Logical NOT function object class (class template)

Adaptor and conversion functions

Negators
not1
Return negation of unary function object (function template)
not2
Return negation of binary function object (function template)

Parameter binders
bind1st
Return function object with first parameter bound (function template)
bind2nd
Return function object with second parameter bound (function template)

Conversors
ptr_fun
Convert function pointer to function object (function template)
mem_fun
Convert member function to function object (pointer version) (function template)
mem_fun_ref
Convert member function to function object (reference version) (function template)

Instrumental types

unary_negate
Negate unary function object class (class template)
binary_negate
Negate binary function object class (class template)
binder1st
Generate function object class with 1st parameter bound (class template)
binder2nd
Generate function object class with 2nd parameter bound (class template)
pointer_to_unary_function
Generate unary function object class from pointer (class template)
pointer_to_binary_function
Generate binary function object class from pointer (class template)
mem_fun_t
Generate function object class from parameterless member (pointer version) (class template)
mem_fun1_t
Generate function object class from single-parameter member (pointer version) (class template)
const_mem_fun_t
Generate function object class from const parameterless member (pointer version) (class template)
const_mem_fun1_t
Generate function object class from single-parameter const member (pointer version) (class template)
mem_fun_ref_t
Generate function object class from parameterless member (reference version) (class template)
mem_fun1_ref_t
Generate function object class from single-parameter member (reference version) (class template)
const_mem_fun_ref_t
Generate function object class from const parameterless member (reference version) (class template)
const_mem_fun1_ref_t
Generate function object class from single-parameter const member (reference version) (class template)

Functions

These functions create objects of wrapper classes based on its arguments:
bind
Bind function arguments (function template)
cref
Construct reference_wrapper to const (function template)
mem_fn
Convert member function to function object (function template)
not1
Return negation of unary function object (function template)
not2
Return negation of binary function object (function template)
ref
Construct reference_wrapper (function template)

Classes


Wrapper classes

Wrapper classes are classes that hold an object and have an interface similar to that object, but adding or changing some of its features:
binary_negate
Negate binary function object class (class template)
function
Function wrapper (class template)
reference_wrapper
Reference wrapper (class template)
unary_negate
Negate unary function object class (class template)

Operator classes

Operator classes are classes that define functional objects that call operators:
bit_and
Bitwise AND function object class (class template)
bit_or
Bitwise OR function object class (class template)
bit_xor
Bitwise XOR function object class (class template)
divides
Division function object class (class template)
equal_to
Function object class for equality comparison (class template)
greater
Function object class for greater-than inequality comparison (class template)
greater_equal
Function object class for greater-than-or-equal-to comparison (class template)
less
Function object class for less-than inequality comparison (class template)
less_equal
Function object class for less-than-or-equal-to comparison (class template)
logical_and
Logical AND function object class (class template)
logical_not
Logical NOT function object class (class template)
logical_or
Logical OR function object class (class template)
minus
Subtraction function object class (class template)
modulus
Modulus function object class (class template)
multiplies
Multiplication function object class (class template)
negate
Negative function object class (class template)
not_equal_to
Function object class for non-equality comparison (class template)
plus
Addition function object class (class template)

Other classes

bad_function_call
Exception thrown on bad call (class)
hash
Default hash function object class (class template)
is_bind_expression
Is bind expression (class template)
is_placeholder
Is placeholder (class template)

Namespaces

placeholders
Bind argument placeholders (namespace)