dlinear::drake::symbolic::Environment Class Reference

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

#include <symbolic_environment.h>

Public Types
typedef map::value_type	value_type
	std::pair<key_type, mapped_type>

Public Member Functions
	Environment ()=default
	Default constructor.
	~Environment ()=default
	Default destructor.
	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.
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.
std::pair< Environment::iterator, bool >	insert (const key_type &key, const mapped_type &elem)
	Inserts a pair (key, elem).
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.
const mapped_type &	at (const key_type &key) const
	Returns the value that is mapped to a key equivalent to key.
std::size_t	erase (const key_type &key)
	Erases the element with specific key.
void	erase (const iterator &pos)
	Erases the element at the specified pos.
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.
bool	contains (const key_type &key) const
	Checks whether the environment contains a variable key.

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 mpq_class& res1 = e1.Evaluate(env);  // x + y => 2.0 + 3.0 =>  5.0
const mpq_class& 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

Note that it is not allowed to have a dummy variable in an environment. It throws std::runtime_error for the attempts to create an environment with a dummy variable, to insert a dummy variable to an existing environment, or to take a reference to a value mapped to a dummy variable. See the following examples.

Variable    var_dummy{};           // OK to have a dummy variable
Environment e1{var_dummy};         // throws std::runtime_error exception
Environment e2{{var_dummy, 1.0}};  // throws std::runtime_error exception
Environment e{};
e.insert(var_dummy, 1.0);          // throws std::runtime_error exception
e[var_dummy] = 3.0;                // throws std::runtime_error exception

Definition at line 51 of file symbolic_environment.h.

Constructor & Destructor Documentation

Environment() [1/2]

dlinear::drake::symbolic::Environment::Environment

(

std::initializer_list< value_type >

init

)

List constructor.

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

Environment() [2/2]

dlinear::drake::symbolic::Environment::Environment

(

std::initializer_list< key_type >

vars

)

List constructor.

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

Member Function Documentation

empty()

bool dlinear::drake::symbolic::Environment::empty ( ) const

inline

Checks whether the container is empty.

Definition at line 101 of file symbolic_environment.h.

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

• third_party/com_github_robotlocomotion_drake/dlinear/symbolic/symbolic_environment.h