Environment Class Reference

Detailed Description

Represents a symbolic environment (mapping from a variable to a value).

This class is used when we evaluate symbolic expressions or formulas which include unquantified (free) variables. Here are examples:

const Variable var_x{"x"};
const Variable var_y{"y"};
const Expression x{var_x};
const Expression y{var_x};
const Expression e1{x + y};
const Expression e2{x - y};
const Formula f{e1 > e2};
 
// env maps var_x to 2.0 and var_y to 3.0
const Environment env{{var_x, 2.0}, {var_y, 3.0}};
 
const double res1 = e1.Evaluate(env);  // x + y => 2.0 + 3.0 =>  5.0
const double res2 = e2.Evaluate(env);  // x - y => 2.0 - 3.0 => -1.0
const bool res = f.Evaluate(env);  // x + y > x - y => 5.0 >= -1.0 => True

#include <drake/common/symbolic/expression/environment.h>

Public Types
typedef Variable	key_type
typedef double	mapped_type
typedef std::unordered_map< key_type, mapped_type >	map
typedef map::value_type	value_type
	std::pair<key_type, mapped_type>
typedef map::iterator	iterator
typedef map::const_iterator	const_iterator

Public Member Functions
	Environment ()=default
	Default constructor.
	Environment (std::initializer_list< value_type > init)
	List constructor.
	Environment (std::initializer_list< key_type > vars)
	List constructor.
	Environment (map m)
	Constructs an environment from m (of map type, which is std::unordered_map).
	~Environment ()
iterator	begin ()
	Returns an iterator to the beginning.
iterator	end ()
	Returns an iterator to the end.
const_iterator	begin () const
	Returns a const iterator to the beginning.
const_iterator	end () const
	Returns a const iterator to the end.
const_iterator	cbegin () const
	Returns a const iterator to the beginning.
const_iterator	cend () const
	Returns a const iterator to the end.
void	insert (const key_type &key, const mapped_type &elem)
	Inserts a pair (key, elem) if this environment doesn't contain key.
void	insert (const Eigen::Ref< const MatrixX< key_type > > &keys, const Eigen::Ref< const MatrixX< mapped_type > > &elements)
	Given a matrix of symbolic variables keys and a matrix of values elements, inserts each pair (keys(i, j), elements(i, j)) into the environment if this environment doesn't contain keys(i, j) .
bool	empty () const
	Checks whether the container is empty.
size_t	size () const
	Returns the number of elements.
iterator	find (const key_type &key)
	Finds element with specific key.
const_iterator	find (const key_type &key) const
	Finds element with specific key.
Variables	domain () const
	Returns the domain of this environment.
std::string	to_string () const
	Returns string representation.
mapped_type &	operator[] (const key_type &key)
	Returns a reference to the value that is mapped to a key equivalent to key, performing an insertion if such key does not already exist.
const mapped_type &	operator[] (const key_type &key) const
	As above, but returns a constref and does not perform an insertion (throwing a runtime error instead) if the key does not exist.
Implements CopyConstructible, CopyAssignable, MoveConstructible, MoveAssignable
	Environment (const Environment &)=default
Environment &	operator= (const Environment &)=default
	Environment (Environment &&)=default
Environment &	operator= (Environment &&)=default

Friends
std::ostream &	operator<< (std::ostream &os, const Environment &env)

Member Typedef Documentation

const_iterator

typedef map::const_iterator const_iterator

iterator

typedef map::iterator iterator

key_type

typedef Variable key_type

map

typedef std::unordered_map<key_type, mapped_type> map

mapped_type

typedef double mapped_type

value_type

typedef map::value_type value_type

std::pair<key_type, mapped_type>

Constructor & Destructor Documentation

Environment() [1/6]

Environment ( const Environment & )

default

Environment() [2/6]

Environment ( Environment && )

default

Environment() [3/6]

Environment ( )

default

Default constructor.

Environment() [4/6]

Environment

(

std::initializer_list< value_type >

init

)

List constructor.

Constructs an environment from a list of (Variable * double).

Exceptions

std::exception

if init include a dummy variable or a NaN value.

Environment() [5/6]

Environment

(

std::initializer_list< key_type >

vars

)

List constructor.

Constructs an environment from a list of Variable. Initializes the variables with 0.0.

Exceptions

std::exception

if vars include a dummy variable.

Environment() [6/6]

Environment ( map m )

explicit

Constructs an environment from m (of map type, which is std::unordered_map).

Exceptions

std::exception

if m include a dummy variable or a NaN value.

~Environment()

~Environment

(

)

Member Function Documentation

begin() [1/2]

iterator begin

(

)

Returns an iterator to the beginning.

begin() [2/2]

const_iterator begin ( ) const

nodiscard

Returns a const iterator to the beginning.

cbegin()

const_iterator cbegin ( ) const

nodiscard

Returns a const iterator to the beginning.

cend()

const_iterator cend ( ) const

nodiscard

Returns a const iterator to the end.

domain()

Variables domain ( ) const

nodiscard

Returns the domain of this environment.

empty()

bool empty ( ) const

nodiscard

Checks whether the container is empty.

end() [1/2]

iterator end

(

)

Returns an iterator to the end.

end() [2/2]

const_iterator end ( ) const

nodiscard

Returns a const iterator to the end.

find() [1/2]

iterator find

(

const key_type &

key

)

Finds element with specific key.

find() [2/2]

const_iterator find ( const key_type & key ) const

nodiscard

Finds element with specific key.

insert() [1/2]

void insert	(	const Eigen::Ref< const MatrixX< key_type > > &	keys,
		const Eigen::Ref< const MatrixX< mapped_type > > &	elements )

Given a matrix of symbolic variables keys and a matrix of values elements, inserts each pair (keys(i, j), elements(i, j)) into the environment if this environment doesn't contain keys(i, j) .

Similar to insert function in map, if keys(i, j) already exists in this environment, then this function doesn't change the its existing value in this environment.

Exceptions

std::exception

if the size of keys is different from the size of elements.

insert() [2/2]

void insert	(	const key_type &	key,
		const mapped_type &	elem )

Inserts a pair (key, elem) if this environment doesn't contain key.

Similar to insert function in map, if the key already exists in this environment, then calling insert(key, elem) doesn't change the existing key-value in this environment.

operator=() [1/2]

Environment & operator= ( const Environment & )

default

operator=() [2/2]

Environment & operator= ( Environment && )

default

operator[]() [1/2]

mapped_type & operator[]

(

const key_type &

key

)

Returns a reference to the value that is mapped to a key equivalent to key, performing an insertion if such key does not already exist.

operator[]() [2/2]

const mapped_type & operator[]

(

const key_type &

key

)

const

As above, but returns a constref and does not perform an insertion (throwing a runtime error instead) if the key does not exist.

size()

size_t size ( ) const

nodiscard

Returns the number of elements.

to_string()

std::string to_string ( ) const

nodiscard

Returns string representation.

Friends And Related Symbol Documentation

operator<<

std::ostream & operator<< ( std::ostream & os, const Environment & env )

friend

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The documentation for this class was generated from the following file:

• drake/common/symbolic/expression/environment.h