Detailed Description

A wrapper of exprtk runtime expression compiler: it takes a string representing an expression (from a simple mathematical formula to a complete program), compiles it and evaluates its result as many times as required.

The result will change as the "variables" appearing in the expression (hold and managed by the user of this object) change.

Refer to exprtk documentation for reference on supported formulas, control flow instructions, etc.

This wrapper is provided to reduce the (very large) compilation time and memory required by the original library, at the cost of only exposing the most commonly used part of its API:

Only expressions returning double are supported.
Variables must be provided via a std::map container or pointers to user-stored variables.

See examples of usage in the unit test file.

If the environment variable MRPT_EXPR_VERBOSE=1 is defined, debug information will be dumped to std::cout explaining the values of all the involved variables upon each call to eval(). Alternatively, the env var MRPT_EXPR_VERBOSE can be set to a list of terms split by |, and only those formulas that match (i.e. contain as substrings) any of the terms will be traced. Example: MRPT_EXPR_VERBOSE="cos|sin|speed|if (x>0)".

Note: (New in MRPT 1.5.0); (MRPT_EXPR_VERBOSE new in MRPT 1.5.7)

Definition at line 49 of file CRuntimeCompiledExpression.h.

#include <mrpt/math/CRuntimeCompiledExpression.h>

Classes
struct	ExprVerbose

Public Member Functions
	CRuntimeCompiledExpression ()
	Default ctor. More...

void	compile (const std::string &expression, const std::map< std::string, double > &variables=std::map< std::string, double >(), const std::string &expr_name_for_error_reporting=std::string())
	Initializes the object by compiling an expression. More...

void	register_symbol_table (const std::map< std::string, double *> &variables)
	Can be used before calling compile() to register additional variables by means of pointers instead of a std::map. More...

double	eval () const
	Evaluates the current value of the precompiled formula. More...

bool	is_compiled () const
	Returns true if compile() was called and ended without errors. More...

const std::string &	get_original_expression () const
	Returns the original formula passed to compile(), or an empty string if still not compiled. More...

exprtk::expression< double > &	get_raw_exprtk_expr ()
	Access raw exprtk expression object. More...

const exprtk::expression< double > &	get_raw_exprtk_expr () const
	Access raw exprtk expression object. More...

Private Member Functions
	PIMPL_DECLARE_TYPE (exprtk::expression< double >, m_compiled_formula)

Private Attributes
std::string	m_original_expr_str

Friends
struct	ExprVerbose

Constructor & Destructor Documentation

◆ CRuntimeCompiledExpression()

CRuntimeCompiledExpression::CRuntimeCompiledExpression ( )

Default ctor.

Definition at line 54 of file CRuntimeCompiledExpression.cpp.

References PIMPL_CONSTRUCT.

Member Function Documentation

◆ compile()

void CRuntimeCompiledExpression::compile	(	const std::string &	expression,
		const std::map< std::string, double > &	variables = `std::map<std::string, double>()`,
		const std::string &	expr_name_for_error_reporting = `std::string()`
	)

Initializes the object by compiling an expression.

Exceptions

std::runtime_error On any syntax error or undefined symbol while compiling the expression. The e.what() message describes what is exactly the problem.

See also: register_symbol_table()

Parameters

[in]	expression	The expression to be compiled.
[in]	variables	Map of variables/constants by `name` -> `value`. The references to the values in this map must be ensured to be valid thoughout all the life of the compiled expression.
	expr_name_for_error_reporting	A descriptive name of this formula, to be used when generating error reports via an exception, if needed

Definition at line 59 of file CRuntimeCompiledExpression.cpp.

References m_original_expr_str, M_PI, PIMPL_GET_REF, and THROW_EXCEPTION_FMT.

Referenced by mrpt::nav::CPTG_Holo_Blend::internal_initialize(), mrpt::utils::simpleini::MRPT_IniFileParser::parse_process_var_eval(), and TEST().

◆ eval()

double CRuntimeCompiledExpression::eval ( ) const

Evaluates the current value of the precompiled formula.

Exceptions

std::runtime_error If the formula has not been compiled yet.

Definition at line 82 of file CRuntimeCompiledExpression.cpp.

References ASSERT_, mrpt::math::CRuntimeCompiledExpression::ExprVerbose::Instance(), PIMPL_GET_CONSTREF, and mrpt::math::CRuntimeCompiledExpression::ExprVerbose::process().

Referenced by mrpt::nav::CPTG_Holo_Blend::internal_get_T_ramp(), mrpt::nav::CPTG_Holo_Blend::internal_get_v(), mrpt::nav::CPTG_Holo_Blend::internal_get_w(), mrpt::utils::simpleini::MRPT_IniFileParser::parse_process_var_eval(), and TEST().

◆ get_original_expression()

const std::string & CRuntimeCompiledExpression::get_original_expression ( ) const

Returns the original formula passed to compile(), or an empty string if still not compiled.

Definition at line 143 of file CRuntimeCompiledExpression.cpp.

◆ get_raw_exprtk_expr() [1/2]

exprtk::expression< double > & CRuntimeCompiledExpression::get_raw_exprtk_expr ( )

Access raw exprtk expression object.

Definition at line 130 of file CRuntimeCompiledExpression.cpp.

References ASSERT_, and PIMPL_GET_REF.

◆ get_raw_exprtk_expr() [2/2]

const exprtk::expression< double > & CRuntimeCompiledExpression::get_raw_exprtk_expr ( ) const

Access raw exprtk expression object.

Definition at line 134 of file CRuntimeCompiledExpression.cpp.

References ASSERT_, and PIMPL_GET_CONSTREF.

◆ is_compiled()

bool CRuntimeCompiledExpression::is_compiled ( ) const

Returns true if compile() was called and ended without errors.

Definition at line 139 of file CRuntimeCompiledExpression.cpp.

◆ PIMPL_DECLARE_TYPE()

mrpt::math::CRuntimeCompiledExpression::PIMPL_DECLARE_TYPE	(	exprtk::expression< double >	,
		m_compiled_formula
	)

private

◆ register_symbol_table()

void CRuntimeCompiledExpression::register_symbol_table ( const std::map< std::string, double *> & variables )

Can be used before calling compile() to register additional variables by means of pointers instead of a std::map.

Parameters

[in] variables Map of variables/constants by name -> value. The references to the values in this map must be ensured to be valid thoughout all the life of the compiled expression.

Definition at line 118 of file CRuntimeCompiledExpression.cpp.

References PIMPL_GET_REF.

Referenced by mrpt::nav::CPTG_Holo_Blend::internal_construct_exprs().