FGFunction Class Reference

Detailed Description

Represents a mathematical function.

The FGFunction class is a powerful and versatile resource that allows algebraic functions to be defined in a JSBSim configuration file. It is similar in concept to MathML (Mathematical Markup Language, www.w3.org/Math/), but simpler and more terse. A function definition consists of an operation, a value, a table, or a property (which evaluates to a value). The currently supported operations are:

• sum (takes n args)
• difference (takes n args)
• product (takes n args)
• quotient (takes 2 args)
• pow (takes 2 args)
• sqrt (takes one argument)
• toradians (takes one argument)
• todegrees (takes one argument)
• exp (takes 2 args)
• log2 (takes 1 arg)
• ln (takes 1 arg)
• log10 (takes 1 arg)
• abs (takes 1 arg)
• sin (takes 1 arg)
• cos (takes 1 arg)
• tan (takes 1 arg)
• asin (takes 1 arg)
• acos (takes 1 arg)
• atan (takes 1 arg)
• atan2 (takes 2 args)
• min (takes n args)
• max (takes n args)
• avg (takes n args)
• fraction
• mod
• floor (takes 1 arg)
• ceil (takes 1 arg)
• fmod (takes 2 args)
• roundmultiple (takes 2 args)
• lt (less than, takes 2 args)
• le (less equal, takes 2 args)
• gt (greater than, takes 2 args)
• ge (greater than, takes 2 args)
• eq (equal, takes 2 args)
• nq (not equal, takes 2 args)
• and (takes n args)
• or (takes n args)
• not (takes 1 args)
• if-then (takes 2-3 args)
• switch (takes 2 or more args)
• random (Gaussian distribution random number)
• urandom (Uniform random number between -1 and +1)
• pi
• integer
• interpolate 1-dimensional (takes a minimum of five arguments, odd number)

An operation is defined in the configuration file as in the following example:

<sum>
  <value> 3.14159 </value>
  <property> velocities/qbar </property>
  <product>
    <value> 0.125 </value>
    <property> metrics/wingarea </property>
  </product>
</sum>

A full function definition, such as is used in the aerodynamics section of a configuration file includes the function element, and other elements. It should be noted that there can be only one non-optional (non-documentation) element - that is, one operation element or one table element - in the top-level function definition. Multiple value and/or property elements cannot be immediate child members of the function element. Almost always, the first operation within the function element will be a product or sum. For example:

<function name="aero/moment/Clr">
    <description>Roll moment due to yaw rate</description>
    <product>
        <property>aero/qbar-area</property>
        <property>metrics/bw-ft</property>
        <property>aero/bi2vel</property>
        <property>velocities/r-aero-rad_sec</property>
        <table>
            <independentVar>aero/alpha-rad</independentVar>
            <tableData>
                 0.000  0.08
                 0.094  0.19
            </tableData>
        </table>
    </product>
</function>

The "lowest level" in a function is always a value or a property, which cannot itself contain another element. As shown, operations can contain values, properties, tables, or other operations. In the first above example, the sum element contains all three. What is evaluated is written algebraically as:

3.14159 + qbar + (0.125 * wingarea) 

Some operations can take only a single argument. That argument, however, can be an operation (such as sum) which can contain other items. The point to keep in mind is that it evaluates to a single value - which is just what the trigonometric functions require (except atan2, which takes two arguments).

Specific Function Definitions

Note: In the definitions below, a "property" refers to a single property specified within either the <property></property> tag or the shortcut tag, <p></p>. The keyword "value" refers to a single numeric value specified either within the <value></value> tag or the shortcut <v></v> tag. The keyword "table" refers to a single table specified either within the <table></table> tag or the shortcut <t></t> tag. The plural form of any of the three words refers to one or more instances of a property, value, or table.

• sum, sums the values of all immediate child elements:

  <sum>
    {properties, values, tables, or other function elements}
  </sum>
   
  Example: Mach + 0.01
   
  <sum>
    <p> velocities/mach </p>
    <v> 0.01 </v>
  </sum>

• difference, subtracts the values of all immediate child elements from the value of the first child element:

  <difference>
    {properties, values, tables, or other function elements}
  </difference>
   
  Example: Mach - 0.01
   
  <difference>
    <p> velocities/mach </p>
    <v> 0.01 </v>
  </difference>

• product multiplies together the values of all immediate child elements:

  <product>
    {properties, values, tables, or other function elements}
  </product>
   
  Example: qbar*S*beta*CY_beta
   
  <product>
    <property> aero/qbar-psf            </property>
    <property> metrics/Sw-sqft          </property>
    <property> aero/beta-rad            </property>
    <property> aero/coefficient/CY_beta </property>
  </product>

• quotient, divides the value of the first immediate child element by the second immediate child element:

  <quotient>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </quotient>
   
  Example: (2*GM)/R
   
  <quotient>
    <product>
      <v> 2.0 </v>
      <p> guidance/executive/gm </p>
    </product>
    <p> position/radius-to-vehicle-ft </p>
  </quotient>

• pow, raises the value of the first immediate child element to the power of the value of the second immediate child element:

  <pow>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </pow>
   
  Example: Mach^2
   
  <pow>
    <p> velocities/mach </p>
    <v> 2.0 </v>
  </pow>

• sqrt, takes the square root of the value of the immediate child element:

  <sqrt>
    {property, value, table, or other function element}
  </sqrt>
   
  Example: square root of 25
   
  <sqrt> <v> 25.0 </v> </sqrt>

• toradians, converts a presumed argument in degrees to radians by multiplying the value of the immediate child element by pi/180:

  <toradians>
    {property, value, table, or other function element}
  </toradians>
   
  Example: convert 45 degrees to radians
   
  <toradians> <v> 45 </v> </toradians>

• todegrees, converts a presumed argument in radians to degrees by multiplying the value of the immediate child element by 180/pi:

  <todegrees>
    {property, value, table, or other function element}
  </todegrees>
   
  Example: convert 0.5*pi radians to degrees
   
  <todegrees>
    <product> <v> 0.5 </v> <pi/> </product>
  </todegrees>

• exp, raises "e" to the power of the immediate child element:

  <exp>
    {property, value, table, or other function element}
  </exp>
   
  Example: raise "e" to the 1.5 power, e^1.5
   
  <exp> <v> 1.5 </v> </exp>

• log2, calculates the log base 2 value of the immediate child element:

  <log2>
    {property, value, table, or other function element} 
  </log2>
   
  Example:
  <log2> <v> 128 </v> </log2>

• ln, calculates the natural logarithm of the value of the immediate child element:

  <ln>
    {property, value, table, or other function element}
  </ln>
   
  Example: ln(128)
   
  <ln> <v> 200 </v> </ln>

• log10, calculates the base 10 logarithm of the value of the immediate child element

  <log10>
    {property, value, table, or other function element}
  </log10>
   
  Example log(Mach)
   
  <log10> <p> velocities/mach </p> </log10>

• abs calculates the absolute value of the immediate child element

  <abs>
    {property, value, table, or other function element}
  </abs>
   
  Example:
   
  <abs> <p> flight-path/gamma-rad </p> </abs>

• sin, calculates the sine of the value of the immediate child element (the argument is expected to be in radians)

  <sin>
    {property, value, table, or other function element}
  </sin>
   
  Example:
   
  <sin> <toradians> <p> fcs/heading-true-degrees </p> </toradians> </sin>

• cos, calculates the cosine of the value of the immediate child element (the argument is expected to be in radians)

  <cos>
    {property, value, table, or other function element}
  </cos>
   
  Example:
   
  <cos> <toradians> <p> fcs/heading-true-degrees </p> </toradians> </cos>

• tan, calculates the tangent of the value of the immediate child element (the argument is expected to be in radians)

  <tan>
    {property, value, table, or other function element}
  </tan>
   
  Example:
   
  <tan> <toradians> <p> fcs/heading-true-degrees </p> </toradians> </tan>

• asin, calculates the arcsine (inverse sine) of the value of the immediate child element. The value provided should be in the range from -1 to +1. The value returned will be expressed in radians, and will be in the range from -pi/2 to +pi/2.

  <asin>
    {property, value, table, or other function element}
  </asin>
   
  Example:
   
  <asin> <v> 0.5 </v> </asin>

• acos, calculates the arccosine (inverse cosine) of the value of the immediate child element. The value provided should be in the range from -1 to +1. The value returned will be expressed in radians, and will be in the range from 0 to pi.

  <acos>
    {property, value, table, or other function element}
  </acos>
   
  Example:
   
  <acos> <v> 0.5 </v> </acos>

• atan, calculates the inverse tangent of the value of the immediate child element. The value returned will be expressed in radians, and will be in the range from -pi/2 to +pi/2.

  <atan>
    {property, value, table, or other function element}
  </atan>
   
  Example:
   
  <atan> <v> 0.5 </v> </atan>

• atan2 calculates the inverse tangent of the value of the immediate child elements, Y/X (in that order). It even works for X values near zero. The value returned will be expressed in radians, and in the range -pi to +pi.

  <atan2>
    {property, value, table, or other function element} {property, value, table, or other function element}
  </atan2>
   
  Example: inverse tangent of 0.5/0.25, evaluates to: 1.107 radians
   
  <atan2> <v> 0.5 </<v> <v> 0.25 </v> </atan2>

• min returns the smallest value from all the immediate child elements

  <min>
    {properties, values, tables, or other function elements}
  </min>
   
  Example: returns the lesser of velocity and 2500
   
  <min>
    <p> velocities/eci-velocity-mag-fps </p>
    <v> 2500.0 </v>
  </min>

• max returns the largest value from all the immediate child elements

  <max>
    {properties, values, tables, or other function elements}
  </max>
   
  Example: returns the greater of velocity and 15000
   
  <max>
    <p> velocities/eci-velocity-mag-fps </p>
    <v> 15000.0 </v>
  </max>

• avg returns the average value of all the immediate child elements

  <avg>
    {properties, values, tables, or other function elements} 
  </avg>
   
  Example: returns the average of the four numbers below, evaluates to 0.50.
   
  <avg>
    <v> 0.25 </v>
    <v> 0.50 </v>
    <v> 0.75 </v>
    <v> 0.50 </v>
  </avg>

• fraction, returns the fractional part of the value of the immediate child element

  <fraction>
    {property, value, table, or other function element}
  </fraction>
   
  Example: returns the fractional part of pi - or, roughly, 0.1415926...
   
  <fraction> <pi/> </fraction>

• integer, returns the integer portion of the value of the immediate child element

  <integer>
    {property, value, table, or other function element}
  </integer>

• mod returns the remainder from the integer division of the value of the first immediate child element by the second immediate child element, X/Y (X modulo Y). The value returned is the value X-I*Y, for the largest integer I such that if Y is nonzero, the result has the same sign as X and magnitude less than the magnitude of Y. For instance, the expression "5 mod 2" would evaluate to 1 because 5 divided by 2 leaves a quotient of 2 and a remainder of 1, while "9 mod 3" would evaluate to 0 because the division of 9 by 3 has a quotient of 3 and leaves a remainder of 0.

  <mod>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </mod>
   
  Example: 5 mod 2, evaluates to 1
   
  <mod> <v> 5 </v> <v> 2 </v> </mod>

• floor returns the largest integral value that is not greater than X.

  <floor>
    {property, value, table, or other function element}
  </floor>

  Examples: floor(2.3) evaluates to 2.0 while floor(-2.3) evaluates to -3.0
• ceil returns the smallest integral value that is not less than X.

  <ceil>
    {property, value, table, or other function element}
  </ceil>

  Examples: ceil(2.3) evaluates to 3.0 while ceil(-2.3) evaluates to -2.0
• fmod returns the floating-point remainder of X/Y (rounded towards zero)

  <fmod>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </fmod>

  Example: fmod(18.5, 4.2) evaluates to 1.7
• roundmultiple returns the floating-point rounding of X to a multiple of M. round(X/M) * M

  <roundmultiple>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </roundmultiple>

  Example: roundmultiple(93.43, 5.0) evaluates to 95.0
• lt returns a 1 if the value of the first immediate child element is less than the value of the second immediate child element, returns 0 otherwise

  <lt>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </lt>
   
  Example: returns 1 if thrust is less than 10,000, returns 0 otherwise
   
  <lt>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 10000.0 </v>
  </lt>

• le, returns a 1 if the value of the first immediate child element is less than or equal to the value of the second immediate child element, returns 0 otherwise

  <le>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </le>
   
  Example: returns 1 if thrust is less than or equal to 10,000, returns 0 otherwise
   
  <le>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 10000.0 </v>
  </le>

• gt returns a 1 if the value of the first immediate child element is greater than the value of the second immediate child element, returns 0 otherwise

  <gt>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </gt>
   
  Example: returns 1 if thrust is greater than 10,000, returns 0 otherwise
   
  <gt>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 10000.0 </v>
  </gt>

• ge, returns a 1 if the value of the first immediate child element is greater than or equal to the value of the second immediate child element, returns 0 otherwise

  <ge>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </ge>
   
  Example: returns 1 if thrust is greater than or equal to 10,000, returns 0
  otherwise
   
  <ge>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 10000.0 </v>
  </ge>

• eq returns a 1 if the value of the first immediate child element is equal to the second immediate child element, returns 0 otherwise

  <eq>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </eq>
   
  Example: returns 1 if thrust is equal to 10,000, returns 0 otherwise
   
  <eq>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 10000.0 </v>
  </eq>

• nq returns a 1 if the value of the first immediate child element is not equal to the value of the second immediate child element, returns 0 otherwise

  <nq>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </nq>
   
  Example: returns 1 if thrust is not 0, returns 0 otherwise
   
  <nq>
    <p> propulsion/engine[2]/thrust-lbs </p>
    <v> 0.0 </v>
  </nq>

• and returns a 1 if the values of the immediate child elements are all 1, returns 0 otherwise. Values provided are expected to be either 1 or 0 within machine precision.

  <and>
    {properties, values, tables, or other function elements}
  </and>
   
  Example: returns 1 if the specified flags are all 1
   
  <and>
    <p> guidance/first-stage-flight-flag </p>
    <p> control/engines-running-flag </p>
  </and>

• or returns a 1 if the values of any of the immediate child elements 1, returns 0 otherwise. Values provided are expected to be either 1 or 0 within machine precision.

  <or>
    {properties, values, tables, or other function elements}
  </or>
   
  Example: returns 1 if any of the specified flags are 1
   
  <or>
    <p> guidance/first-stage-flight-flag </p>
    <p> control/engines-running-flag </p>
  </or>

• not, returns the inverse of the value of the supplied immediate child element (e.g., returns 1 if supplied a 0)

  <not>
    {property, value, table, or other function element} 
  </not>
   
  Example: returns 0 if the value of the supplied flag is 1
   
  <not> <p> guidance/first-stage-flight-flag </p> </not>

• ifthen if the value of the first immediate child element is 1, then the value of the second immediate child element is returned, otherwise the value of the third child element is returned

  <ifthen>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
    {property, value, table, or other function element}
  </ifthen>
   
  Example: if flight-mode is greater than 2, then a value of 0.00 is
           returned, otherwise the value of the property control/pitch-lag is
           returned.
   
  <ifthen>
    <gt> <p> executive/flight-mode </p> <v> 2 </v> </gt>
    <v> 0.00 </v>
    <p> control/pitch-lag </p>
  </ifthen>

• switch uses the integer value of the first immediate child element as an index to select one of the subsequent immediate child elements to return the value of

  <switch>
    {property, value, table, or other function element}
    {property, value, table, or other function element}
    {property, value, table, or other function element}
    ...
  </switch>
   
  Example: if flight-mode is 2, the switch function returns 0.50
  <switch>
    <p> executive/flight-mode </p>
    <v> 0.25 </v>
    <v> 0.50 </v>
    <v> 0.75 </v>
    <v> 1.00 </v>
  </switch>

• random Returns a normal distributed random number. The function, without parameters, returns a normal distributed random value with a distribution defined by the parameters mean = 0.0 and standard deviation (stddev) = 1.0 The Mean of the distribution (its expected value, μ). Which coincides with the location of its peak. Standard deviation (σ): The square root of variance, representing the dispersion of values from the distribution mean. This shall be a positive value (σ>0).

  <random/> 
  <random seed="1234"/>
  <random seed="time_now"/>
  <random seed="time_now" mean="0.0" stddev="1.0"/>

• urandom Returns a uniformly distributed random number. The function, without parameters, returns a random value between the minimum value -1.0 and the maximum value of 1.0 The two maximum and minimum values can be modified using the lower and upper parameters.

  <urandom/>
  <random seed="1234"/>
  <random seed="time_now"/>
  <random seed="time_now" lower="-1.0" upper="1.0"/>

• pi Takes no argument and returns the value of Pi

  <pi/>

• interpolate1d returns the result from a 1-dimensional interpolation of the supplied values, with the value of the first immediate child element representing the lookup value into the table, and the following pairs of values representing the independent and dependent values. The first provided child element is expected to be a property. The interpolation does not extrapolate, but holds the highest value if the provided lookup value goes outside of the provided range.

  <interpolate1d>
    {property, value, table, or other function element}
    {property, value, table, or other function element} {property, value, table, or other function element}
    ...
  </interpolate1d>
   
  Example: If mach is 0.4, the interpolation will return 0.375. If mach is
           1.5, the interpolation will return 0.60.
   
  <interpolate1d>
    <p> velocities/mach </p>
    <v> 0.00 </v>  <v> 0.25 </v>
    <v> 0.80 </v>  <v> 0.50 </v>
    <v> 0.90 </v>  <v> 0.60 </v>
  </interpolate1d>

  Author

  Jon Berndt

Definition at line 764 of file FGFunction.h.

#include <FGFunction.h>

Inheritance diagram for FGFunction:

Collaboration diagram for FGFunction:

Public Types
enum class	OddEven { Either , Odd , Even }
Public Types inherited from FGJSBBase
enum	{ eL = 1 , eM , eN }
	Moments L, M, N. More...
enum	{ eP = 1 , eQ , eR }
	Rates P, Q, R. More...
enum	{ eU = 1 , eV , eW }
	Velocities U, V, W. More...
enum	{ eX = 1 , eY , eZ }
	Positions X, Y, Z. More...
enum	{ ePhi = 1 , eTht , ePsi }
	Euler angles Phi, Theta, Psi. More...
enum	{ eDrag = 1 , eSide , eLift }
	Stability axis forces, Drag, Side force, Lift. More...
enum	{ eRoll = 1 , ePitch , eYaw }
	Local frame orientation Roll, Pitch, Yaw. More...
enum	{ eNorth = 1 , eEast , eDown }
	Local frame position North, East, Down. More...
enum	{ eLat = 1 , eLong , eRad }
	Locations Radius, Latitude, Longitude. More...
enum	{   inNone = 0 , inDegrees , inRadians , inMeters ,   inFeet }
	Conversion specifiers. More...

Public Member Functions
	FGFunction ()
	Default constructor.
	FGFunction (FGFDMExec *fdmex, Element *element, const std::string &prefix="", FGPropertyValue *var=0L)
	Constructor.
	FGFunction (std::shared_ptr< FGPropertyManager > pm)
	~FGFunction (void) override
	Destructor Make sure the function is untied before destruction.
void	cacheValue (bool shouldCache)
	Specifies whether to cache the value of the function, so it is calculated only once per frame.
std::string	GetName (void) const override
	Retrieves the name of the function.
double	GetValue (void) const override
	Retrieves the value of the function object.
std::string	GetValueAsString (void) const
	The value that the function evaluates to, as a string.
bool	IsConstant (void) const override
	Does the function always return the same result (i.e.
Public Member Functions inherited from FGParameter
double	getDoubleValue (void) const
Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.
virtual	~FGJSBBase ()
	Destructor for FGJSBBase.
void	disableHighLighting (void)
	Disables highlighting in the console output.

Protected Member Functions
virtual void	bind (Element *, const std::string &)
void	CheckMaxArguments (Element *el, unsigned int _max)
void	CheckMinArguments (Element *el, unsigned int _min)
void	CheckOddOrEvenArguments (Element *el, OddEven odd_even)
std::string	CreateOutputNode (Element *el, const std::string &Prefix)
void	Load (Element *element, FGPropertyValue *var, FGFDMExec *fdmex, const std::string &prefix="")

Protected Attributes
bool	cached
double	cachedValue
std::vector< FGParameter_ptr >	Parameters
FGPropertyNode_ptr	pNode
std::shared_ptr< FGPropertyManager >	PropertyManager

Additional Inherited Members
Static Public Member Functions inherited from FGJSBBase
static const std::string &	GetVersion (void)
	Returns the version number of JSBSim.
static constexpr double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit.
static constexpr double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine.
static constexpr double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius.
static constexpr double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine.
static constexpr double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin.
static constexpr double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius.
static constexpr double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit.
static constexpr double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin.
static constexpr double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius.
static constexpr double	FeetToMeters (double measure)
	Converts from feet to meters.
static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison.
static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison.
static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison.
static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison.
static constexpr double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.
static constexpr double	sign (double num)
Static Public Attributes inherited from FGJSBBase
static char	highint [5] = {27, '[', '1', 'm', '\0' }
	highlights text
static char	halfint [5] = {27, '[', '2', 'm', '\0' }
	low intensity text
static char	normint [6] = {27, '[', '2', '2', 'm', '\0' }
	normal intensity text
static char	reset [5] = {27, '[', '0', 'm', '\0' }
	resets text properties
static char	underon [5] = {27, '[', '4', 'm', '\0' }
	underlines text
static char	underoff [6] = {27, '[', '2', '4', 'm', '\0' }
	underline off
static char	fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
	blue text
static char	fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
	cyan text
static char	fgred [6] = {27, '[', '3', '1', 'm', '\0' }
	red text
static char	fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
	green text
static char	fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
	default text
static short	debug_lvl = 1
Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)
Static Protected Attributes inherited from FGJSBBase
static constexpr double	radtodeg = 180. / M_PI
static constexpr double	degtorad = M_PI / 180.
static constexpr double	hptoftlbssec = 550.0
static constexpr double	psftoinhg = 0.014138
static constexpr double	psftopa = 47.88
static constexpr double	fttom = 0.3048
static constexpr double	ktstofps = 1852./(3600*fttom)
static constexpr double	fpstokts = 1.0 / ktstofps
static constexpr double	inchtoft = 1.0/12.0
static constexpr double	m3toft3 = 1.0/(fttom*fttom*fttom)
static constexpr double	in3tom3 = inchtoft*inchtoft*inchtoft/m3toft3
static constexpr double	inhgtopa = 3386.38
static constexpr double	slugtolb = 32.174049
	Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff.
static constexpr double	lbtoslug = 1.0/slugtolb
static constexpr double	kgtolb = 2.20462
static constexpr double	kgtoslug = 0.06852168
static const std::string	needed_cfg_version = "2.0"
static const std::string	JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__

Member Enumeration Documentation

OddEven

enum class OddEven

strong

Definition at line 825 of file FGFunction.h.

{Either, Odd, Even};

Constructor & Destructor Documentation

FGFunction() [1/3]

FGFunction ( )

inline

Default constructor.

Definition at line 768 of file FGFunction.h.

    : cached(false), cachedValue(-HUGE_VAL), pNode(nullptr), pCopyTo(nullptr) {}

FGFunction() [2/3]

FGFunction ( std::shared_ptr< FGPropertyManager >  pm )

inlineexplicit

Definition at line 771 of file FGFunction.h.

    : FGFunction()
    { PropertyManager = pm; }

FGFunction() [3/3]

FGFunction	(	FGFDMExec *	fdmex,
		Element *	element,
		const std::string &	prefix = "",
		FGPropertyValue *	var = 0L
	)

Constructor.

When this constructor is called, the XML element pointed to in memory by the element argument is traversed. If other FGParameter-derived objects (values, functions, properties, or tables) are encountered, this instance of the FGFunction object will store a pointer to the found object and pass the relevant Element pointer to the constructor for the new object. In other words, each FGFunction object maintains a list of "child" FGParameter-derived objects which in turn may each contain its own list, and so on. At runtime, each object evaluates its child parameters, which each may have its own child parameters to evaluate.

Parameters

PropertyManager	a pointer to the property manager instance.
element	a pointer to the Element object containing the function definition.
prefix	an optional prefix to prepend to the name given to the property that represents this function (if given).

Definition at line 207 of file FGFunction.cpp.

  : FGFunction(fdmex->GetPropertyManager())
{
  Load(el, var, fdmex, prefix);
  CheckMinArguments(el, 1);
  CheckMaxArguments(el, 1);
 
  string sCopyTo = el->GetAttributeValue("copyto");
 
  if (!sCopyTo.empty()) {
    if (sCopyTo.find("#") != string::npos) {
      if (is_number(prefix))
        sCopyTo = replace(sCopyTo,"#",prefix);
      else {
        cerr << el->ReadFrom() << fgred
             << "Illegal use of the special character '#'" << reset << endl
             << "The 'copyto' argument in function " << Name << " is ignored."
             << endl;
        return;
      }
    }
 
    pCopyTo = PropertyManager->GetNode(sCopyTo);
    if (!pCopyTo)
      cerr << el->ReadFrom() << fgred
           << "Property \"" << sCopyTo
           << "\" must be previously defined in function " << Name << reset
           << "The 'copyto' argument is ignored." << endl;
  }
}

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~FGFunction()

~FGFunction ( void  )

override

Destructor Make sure the function is untied before destruction.

Definition at line 933 of file FGFunction.cpp.

{
  if (pNode && pNode->isTied())
    PropertyManager->Untie(pNode);
 
  Debug(1);
}

Member Function Documentation

bind()

void bind ( Element *  el, const std::string &  Prefix  )

protectedvirtual

Definition at line 1026 of file FGFunction.cpp.

{
  string nName = CreateOutputNode(el, Prefix);
 
  if (!nName.empty())
    PropertyManager->Tie(nName, this, &FGFunction::GetValue);
}

cacheValue()

void cacheValue

(

bool

shouldCache

)

Specifies whether to cache the value of the function, so it is calculated only once per frame.

If shouldCache is true, then the value of the function is calculated, and a flag is set so further calculations done this frame will use the cached value. In order to turn off caching, cacheValue must be called with a false argument.

Parameters

shouldCache

specifies whether the function should cache the computed value.

Definition at line 955 of file FGFunction.cpp.

{
  cached = false; // Must set cached to false prior to calling GetValue(), else
                  // it will _never_ calculate the value;
  if (cache) {
    cachedValue = GetValue();
    cached = true;
  }
}

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CheckMaxArguments()

void CheckMaxArguments ( Element *  el, unsigned int  _max  )

protected

Definition at line 254 of file FGFunction.cpp.

{
  if (Parameters.size() > _max) {
    ostringstream buffer;
    buffer << el->ReadFrom() << fgred << highint
           << "<" << el->GetName() << "> should have no more than " << _max
           << " argument(s)." << reset << endl;
    throw WrongNumberOfArguments(buffer.str(), Parameters, el);
  }
}

CheckMinArguments()

void CheckMinArguments ( Element *  el, unsigned int  _min  )

protected

Definition at line 241 of file FGFunction.cpp.

{
  if (Parameters.size() < _min) {
    ostringstream buffer;
    buffer << el->ReadFrom() << fgred << highint
           << "<" << el->GetName() << "> should have at least " << _min
           << " argument(s)." << reset << endl;
    throw WrongNumberOfArguments(buffer.str(), Parameters, el);
  }
}

CheckOddOrEvenArguments()

void CheckOddOrEvenArguments ( Element *  el, OddEven  odd_even  )

protected

Definition at line 267 of file FGFunction.cpp.

{
 
  switch(odd_even) {
  case OddEven::Even:
    if (Parameters.size() % 2 == 1) {
      cerr << el->ReadFrom() << fgred << highint
           << "<" << el->GetName() << "> must have an even number of arguments."
           << reset << endl;
      throw BaseException("Fatal Error");
    }
    break;
  case OddEven::Odd:
    if (Parameters.size() % 2 == 0) {
      cerr << el->ReadFrom() << fgred << highint
           << "<" << el->GetName() << "> must have an odd number of arguments."
           << reset << endl;
      throw BaseException("Fatal Error");
    }
    break;
  default:
    break;
  }
}

CreateOutputNode()

string CreateOutputNode ( Element *  el, const std::string &  Prefix  )

protected

Definition at line 990 of file FGFunction.cpp.

{
  string nName;
 
  if ( !Name.empty() ) {
    if (Prefix.empty())
      nName  = PropertyManager->mkPropertyName(Name, false);
    else {
      if (is_number(Prefix)) {
        if (Name.find("#") != string::npos) { // if "#" is found
          Name = replace(Name,"#",Prefix);
          nName  = PropertyManager->mkPropertyName(Name, false);
        } else {
          cerr << el->ReadFrom()
               << "Malformed function name with number: " << Prefix
               << " and property name: " << Name
               << " but no \"#\" sign for substitution." << endl;
        }
      } else {
        nName  = PropertyManager->mkPropertyName(Prefix + "/" + Name, false);
      }
    }
 
    pNode = PropertyManager->GetNode(nName, true);
    if (pNode->isTied()) {
      cerr << el->ReadFrom()
           << "Property " << nName << " has already been successfully bound (late)." << endl;
      throw BaseException("Failed to bind the property to an existing already tied node.");
    }
  }
 
  return nName;
}

GetName()

std::string GetName ( void  ) const

inlineoverridevirtual

Retrieves the name of the function.

Implements FGParameter.

Definition at line 809 of file FGFunction.h.

{return Name;}

GetValue()

double GetValue ( void  ) const

overridevirtual

Retrieves the value of the function object.

Returns

the total value of the function.

Implements FGParameter.

Definition at line 967 of file FGFunction.cpp.

{
  if (cached) return cachedValue;
 
  double val = Parameters[0]->GetValue();
 
  if (pCopyTo) pCopyTo->setDoubleValue(val);
 
  return val;
}

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GetValueAsString()

string GetValueAsString

(

void

)

const

The value that the function evaluates to, as a string.

Returns

the value of the function as a string.

Definition at line 980 of file FGFunction.cpp.

{
  ostringstream buffer;
 
  buffer << setw(9) << setprecision(6) << GetValue();
  return buffer.str();
}

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IsConstant()

bool IsConstant ( void  ) const

overridevirtual

Does the function always return the same result (i.e.

does it apply to constant parameters) ?

Reimplemented from FGParameter.

Definition at line 943 of file FGFunction.cpp.

{
  for (auto p: Parameters) {
    if (!p->IsConstant())
      return false;
  }
 
  return true;
}

Load()

void Load ( Element *  element, FGPropertyValue *  var, FGFDMExec *  fdmex, const std::string &  prefix = ""  )

protected

Definition at line 309 of file FGFunction.cpp.

{
  Name = el->GetAttributeValue("name");
  Element* element = el->GetElement();
 
  auto sum = [](const decltype(Parameters)& Parameters)->double {
               double temp = 0.0;
 
               for (auto p: Parameters)
                 temp += p->GetValue();
 
               return temp;
             };
 
  while (element) {
    string operation = element->GetName();
 
    // data types
    if (operation == "property" || operation == "p") {
      string property_name = element->GetDataLine();
 
      if (var && simgear::strutils::strip(property_name) == "#")
        Parameters.push_back(var);
      else {
        if (property_name.find("#") != string::npos) {
          if (is_number(Prefix)) {
            property_name = replace(property_name,"#",Prefix);
          }
          else {
            cerr << element->ReadFrom()
                 << fgred << "Illegal use of the special character '#'"
                 << reset << endl;
            throw BaseException("Fatal Error.");
          }
        }
 
        if (element->HasAttribute("apply")) {
          string function_str = element->GetAttributeValue("apply");
          auto f = fdmex->GetTemplateFunc(function_str);
          if (f)
            Parameters.push_back(new FGFunctionValue(property_name,
                                                     PropertyManager, f, element));
          else {
            cerr << element->ReadFrom()
                 << fgred << highint << "  No function by the name "
                 << function_str << " has been defined. This property will "
                 << "not be logged. You should check your configuration file."
                 << reset << endl;
          }
        }
        else
          Parameters.push_back(new FGPropertyValue(property_name,
                                                   PropertyManager, element));
      }
    } else if (operation == "value" || operation == "v") {
      Parameters.push_back(new FGRealValue(element->GetDataAsNumber()));
    } else if (operation == "pi") {
      Parameters.push_back(new FGRealValue(M_PI));
    } else if (operation == "table" || operation == "t") {
      string call_type = element->GetAttributeValue("type");
      if (call_type == "internal") {
        std::cerr << el->ReadFrom()
                  << "An internal table cannot be nested within a function."
                  << endl;
        throw BaseException("An internal table cannot be nested within a function.");
      }
      Parameters.push_back(new FGTable(PropertyManager, element, Prefix));
      // operations
    } else if (operation == "product") {
      auto f = [](const decltype(Parameters)& Parameters)->double {
                 double temp = 1.0;
 
                 for (auto p: Parameters)
                   temp *= p->GetValue();
 
                 return temp;
               };
      Parameters.push_back(VarArgsFn<decltype(f)>(f, fdmex, element, Prefix, var));
    } else if (operation == "sum") {
      Parameters.push_back(VarArgsFn<decltype(sum)>(sum, fdmex, element, Prefix, var));
    } else if (operation == "avg") {
      auto avg = [&](const decltype(Parameters)& p)->double {
                   return sum(p) / p.size();
                 };
      Parameters.push_back(VarArgsFn<decltype(avg)>(avg, fdmex, element, Prefix, var));
    } else if (operation == "difference") {
      auto f = [](const decltype(Parameters)& Parameters)->double {
                 double temp = Parameters[0]->GetValue();
 
                 for (auto p = Parameters.begin()+1; p != Parameters.end(); ++p)
                   temp -= (*p)->GetValue();
 
                 return temp;
               };
      Parameters.push_back(VarArgsFn<decltype(f)>(f, fdmex, element, Prefix, var));
    } else if (operation == "min") {
      auto f = [](const decltype(Parameters)& Parameters)->double {
                 double _min = HUGE_VAL;
 
                 for (auto p : Parameters) {
                   double x = p->GetValue();
                   if (x < _min)
                     _min = x;
                 }
 
                 return _min;
               };
      Parameters.push_back(VarArgsFn<decltype(f)>(f, fdmex, element, Prefix, var));
    } else if (operation == "max") {
      auto f = [](const decltype(Parameters)& Parameters)->double {
                 double _max = -HUGE_VAL;
 
                 for (auto p : Parameters) {
                   double x = p->GetValue();
                   if (x > _max)
                     _max = x;
                 }
 
                 return _max;
               };
      Parameters.push_back(VarArgsFn<decltype(f)>(f, fdmex, element, Prefix, var));
    } else if (operation == "and") {
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& Parameters)->double {
                 for (auto p : Parameters) {
                   if (!GetBinary(p->GetValue(), ctxMsg)) // As soon as one parameter is false, the expression is guaranteed to be false.
                     return 0.0;
                 }
 
                 return 1.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix,
                                                     var, MaxArgs));
    } else if (operation == "or") {
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& Parameters)->double {
                 for (auto p : Parameters) {
                   if (GetBinary(p->GetValue(), ctxMsg)) // As soon as one parameter is true, the expression is guaranteed to be true.
                     return 1.0;
                 }
 
                 return 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix,
                                                     var, MaxArgs));
    } else if (operation == "quotient") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double y = p[1]->GetValue();
                 return y != 0.0 ? p[0]->GetValue()/y : HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "pow") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return pow(p[0]->GetValue(), p[1]->GetValue());
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "toradians") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue()*M_PI/180.;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "todegrees") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue()*180./M_PI;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "sqrt") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double x = p[0]->GetValue();
                 return x >= 0.0 ? sqrt(x) : -HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "log2") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double x = p[0]->GetValue();
                 return x > 0.0 ? log10(x)*invlog2val : -HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "ln") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double x = p[0]->GetValue();
                 return x > 0.0 ? log(x) : -HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "log10") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double x = p[0]->GetValue();
                 return x > 0.0 ? log10(x) : -HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "sign") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() < 0.0 ? -1 : 1; // 0.0 counts as positive.
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "exp") {
      Parameters.push_back(make_MathFn(exp, fdmex, element, Prefix, var));
    } else if (operation == "abs") {
      Parameters.push_back(make_MathFn(fabs, fdmex, element, Prefix, var));
    } else if (operation == "sin") {
      Parameters.push_back(make_MathFn(sin, fdmex, element, Prefix, var));
    } else if (operation == "cos") {
      Parameters.push_back(make_MathFn(cos, fdmex, element, Prefix, var));
    } else if (operation == "tan") {
      Parameters.push_back(make_MathFn(tan, fdmex, element, Prefix, var));
    } else if (operation == "asin") {
      Parameters.push_back(make_MathFn(asin, fdmex, element, Prefix, var));
    } else if (operation == "acos") {
      Parameters.push_back(make_MathFn(acos, fdmex, element, Prefix, var));
    } else if (operation == "atan") {
      Parameters.push_back(make_MathFn(atan, fdmex, element, Prefix, var));
    } else if (operation == "floor") {
      Parameters.push_back(make_MathFn(floor, fdmex, element, Prefix, var));
    } else if (operation == "ceil") {
      Parameters.push_back(make_MathFn(ceil, fdmex, element, Prefix, var));
    } else if (operation == "fmod") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double y = p[1]->GetValue();
                 return y != 0.0 ? fmod(p[0]->GetValue(), y) : HUGE_VAL;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "roundmultiple") {
      if (element->GetNumElements() == 1)
        Parameters.push_back(make_MathFn(round, fdmex, element, Prefix, var));
      else {
        auto f = [](const decltype(Parameters)& p)->double {
                   double multiple = p[1]->GetValue();
                   return round((p[0]->GetValue() / multiple)) * multiple;
                 };
        Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var, 2));
      }
    } else if (operation == "atan2") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return atan2(p[0]->GetValue(), p[1]->GetValue());
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "mod") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return static_cast<int>(p[0]->GetValue()) % static_cast<int>(p[1]->GetValue());
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "fraction") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double scratch;
                 return modf(p[0]->GetValue(), &scratch);
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "integer") {
      auto f = [](const decltype(Parameters)& p)->double {
                 double result;
                 modf(p[0]->GetValue(), &result);
                 return result;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "lt") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() < p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "le") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() <= p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "gt") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() > p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "ge") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() >= p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "eq") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() == p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "nq") {
      auto f = [](const decltype(Parameters)& p)->double {
                 return p[0]->GetValue() != p[1]->GetValue() ? 1.0 : 0.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix, var));
    } else if (operation == "not") {
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& p)->double {
                 return GetBinary(p[0]->GetValue(), ctxMsg) ? 0.0 : 1.0;
               };
      Parameters.push_back(new aFunc<decltype(f), 1>(f, fdmex, element, Prefix, var));
    } else if (operation == "ifthen") {
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& p)->double {
                 if (GetBinary(p[0]->GetValue(), ctxMsg))
                   return p[1]->GetValue();
                 else
                   return p[2]->GetValue();
               };
      Parameters.push_back(new aFunc<decltype(f), 3>(f, fdmex, element, Prefix, var));
    } else if (operation == "random") {
      double mean = 0.0;
      double stddev = 1.0;
      string mean_attr = element->GetAttributeValue("mean");
      string stddev_attr = element->GetAttributeValue("stddev");
      if (!mean_attr.empty()) {
        try {
          mean = atof_locale_c(mean_attr);
        } catch (InvalidNumber& e) {
          cerr << element->ReadFrom() << e.what() << endl;
          throw e;
        }
      }
      if (!stddev_attr.empty()) {
        try {
          stddev = atof_locale_c(stddev_attr);
        } catch (InvalidNumber& e) {
          cerr << element->ReadFrom() << e.what() << endl;
          throw e;
        }
      }
      auto generator(makeRandomGenerator(element, fdmex));
      auto f = [generator, mean, stddev]()->double {
                 double value = generator->GetNormalRandomNumber();
                 return value*stddev + mean;
               };
      Parameters.push_back(new aFunc<decltype(f), 0>(f, PropertyManager, element,
                                                     Prefix));
    } else if (operation == "urandom") {
      double lower = -1.0;
      double upper = 1.0;
      string lower_attr = element->GetAttributeValue("lower");
      string upper_attr = element->GetAttributeValue("upper");
      if (!lower_attr.empty()) {
        try {
          lower = atof_locale_c(lower_attr);
        } catch (InvalidNumber &e) {
          cerr << element->ReadFrom() << e.what() << endl;
          throw e;
        }
      }
      if (!upper_attr.empty()) {
        try {
          upper = atof_locale_c(upper_attr);
        } catch (InvalidNumber &e) {
          cerr << element->ReadFrom() << e.what() << endl;
          throw e;
        }
      }
      auto generator(makeRandomGenerator(element, fdmex));
      double a = 0.5*(upper-lower);
      double b = 0.5*(upper+lower);
      auto f = [generator, a, b]()->double {
                 double value = generator->GetUniformRandomNumber();
                 return value*a + b;
               };
      Parameters.push_back(new aFunc<decltype(f), 0>(f, PropertyManager, element,
                                                     Prefix));
    } else if (operation == "switch") {
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& p)->double {
                 double temp = p[0]->GetValue();
                 if (temp < 0.0) {
                   cerr << ctxMsg << fgred << highint
                        << "The switch function index (" << temp
                        << ") is negative." << reset << endl;
                   throw BaseException("Fatal error");
                 }
                 size_t n = p.size()-1;
                 size_t i = static_cast<size_t>(temp+0.5);
 
                 if (i < n)
                   return p[i+1]->GetValue();
                 else {
                   cerr << ctxMsg << fgred << highint
                        << "The switch function index (" << temp
                        << ") selected a value above the range of supplied values"
                        << "[0:" << n-1 << "]"
                        << " - not enough values were supplied." << reset << endl;
                   throw BaseException("Fatal error");
                 }
               };
      Parameters.push_back(new aFunc<decltype(f), 2>(f, fdmex, element, Prefix,
                                                     var, MaxArgs));
    } else if (operation == "interpolate1d") {
      auto f = [](const decltype(Parameters)& p)->double {
                 // This is using the bisection algorithm. Special care has been
                 // taken to evaluate each parameter only once.
                 size_t n = p.size();
                 double x = p[0]->GetValue();
                 double xmin = p[1]->GetValue();
                 double ymin = p[2]->GetValue();
                 if (x <= xmin) return ymin;
 
                 double xmax = p[n-2]->GetValue();
                 double ymax = p[n-1]->GetValue();
                 if (x >= xmax) return ymax;
 
                 size_t nmin = 0;
                 size_t nmax = (n-3)/2;
                 while (nmax-nmin > 1) {
                   size_t m = (nmax-nmin)/2+nmin;
                   double xm = p[2*m+1]->GetValue();
                   double ym = p[2*m+2]->GetValue();
                   if (x < xm) {
                     xmax = xm;
                     ymax = ym;
                     nmax= m;
                   } else if (x > xm) {
                     xmin = xm;
                     ymin = ym;
                     nmin = m;
                   }
                   else
                     return ym;
                 }
 
                 return ymin + (x-xmin)*(ymax-ymin)/(xmax-xmin);
               };
      Parameters.push_back(new aFunc<decltype(f), 5>(f, fdmex, element, Prefix,
                                                     var, MaxArgs, OddEven::Odd));
    } else if (operation == "rotation_alpha_local") {
      // Calculates local angle of attack for skydiver body component.
      // Euler angles from the intermediate body frame to the local body frame
      // must be from a z-y-x axis rotation order
      auto f = [](const decltype(Parameters)& p)->double {
                 double alpha = p[0]->GetValue()*degtorad; //angle of attack of intermediate body frame
                 double beta = p[1]->GetValue()*degtorad;  //sideslip angle of intermediate body frame
                 double phi = p[3]->GetValue()*degtorad;   //x-axis Euler angle from the intermediate body frame to the local body frame
                 double theta = p[4]->GetValue()*degtorad; //y-axis Euler angle from the intermediate body frame to the local body frame
                 double psi = p[5]->GetValue()*degtorad;   //z-axis Euler angle from the intermediate body frame to the local body frame
 
                 FGQuaternion qTb2l(phi, theta, psi);
                 double cos_beta = cos(beta);
                 FGColumnVector3 wind_body(cos(alpha)*cos_beta, sin(beta),
                                           sin(alpha)*cos_beta);
                 FGColumnVector3 wind_local = qTb2l.GetT()*wind_body;
 
                 if (fabs(fabs(wind_local(eY)) - 1.0) < 1E-9)
                   return 0.0;
                 else
                   return atan2(wind_local(eZ), wind_local(eX))*radtodeg;
               };
      Parameters.push_back(new aFunc<decltype(f), 6>(f, fdmex, element, Prefix, var));
    } else if (operation == "rotation_beta_local") {
      // Calculates local angle of sideslip for skydiver body component.
      // Euler angles from the intermediate body frame to the local body frame
      // must be from a z-y-x axis rotation order
      auto f = [](const decltype(Parameters)& p)->double {
                 double alpha = p[0]->GetValue()*degtorad; //angle of attack of intermediate body frame
                 double beta = p[1]->GetValue()*degtorad;  //sideslip angle of intermediate body frame
                 double phi = p[3]->GetValue()*degtorad;   //x-axis Euler angle from the intermediate body frame to the local body frame
                 double theta = p[4]->GetValue()*degtorad; //y-axis Euler angle from the intermediate body frame to the local body frame
                 double psi = p[5]->GetValue()*degtorad;   //z-axis Euler angle from the intermediate body frame to the local body frame
                 FGQuaternion qTb2l(phi, theta, psi);
                 double cos_beta = cos(beta);
                 FGColumnVector3 wind_body(cos(alpha)*cos_beta, sin(beta),
                                           sin(alpha)*cos_beta);
                 FGColumnVector3 wind_local = qTb2l.GetT()*wind_body;
 
                 if (fabs(fabs(wind_local(eY)) - 1.0) < 1E-9)
                   return wind_local(eY) > 0.0 ? 0.5*M_PI : -0.5*M_PI;
 
                 double alpha_local = atan2(wind_local(eZ), wind_local(eX));
                 double cosa = cos(alpha_local);
                 double sina = sin(alpha_local);
                 double cosb;
 
                 if (fabs(cosa) > fabs(sina))
                   cosb = wind_local(eX) / cosa;
                 else
                   cosb = wind_local(eZ) / sina;
 
                 return atan2(wind_local(eY), cosb)*radtodeg;
               };
      Parameters.push_back(new aFunc<decltype(f), 6>(f, fdmex, element, Prefix, var));
    } else if (operation == "rotation_gamma_local") {
      // Calculates local roll angle for skydiver body component.
      // Euler angles from the intermediate body frame to the local body frame
      // must be from a z-y-x axis rotation order
      auto f = [](const decltype(Parameters)& p)->double {
                 double alpha = p[0]->GetValue()*degtorad; //angle of attack of intermediate body frame
                 double beta = p[1]->GetValue()*degtorad;  //sideslip angle of intermediate body frame
                 double gamma = p[2]->GetValue()*degtorad; //roll angle of intermediate body frame
                 double phi = p[3]->GetValue()*degtorad;   //x-axis Euler angle from the intermediate body frame to the local body frame
                 double theta = p[4]->GetValue()*degtorad; //y-axis Euler angle from the intermediate body frame to the local body frame
                 double psi = p[5]->GetValue()*degtorad;   //z-axis Euler angle from the intermediate body frame to the local body frame
                 double cos_alpha = cos(alpha), sin_alpha = sin(alpha);
                 double cos_beta = cos(beta),   sin_beta = sin(beta);
                 double cos_gamma = cos(gamma), sin_gamma = sin(gamma);
                 FGQuaternion qTb2l(phi, theta, psi);
                 FGColumnVector3 wind_body_X(cos_alpha*cos_beta, sin_beta,
                                             sin_alpha*cos_beta);
                 FGColumnVector3 wind_body_Y(-sin_alpha*sin_gamma-sin_beta*cos_alpha*cos_gamma,
                                             cos_beta*cos_gamma,
                                             -sin_alpha*sin_beta*cos_gamma+sin_gamma*cos_alpha);
                 FGColumnVector3 wind_local_X = qTb2l.GetT()*wind_body_X;
                 FGColumnVector3 wind_local_Y = qTb2l.GetT()*wind_body_Y;
                 double cosacosb = wind_local_X(eX);
                 double sinb = wind_local_X(eY);
                 double sinacosb = wind_local_X(eZ);
                 double sinc, cosc;
 
                 if (fabs(sinb) < 1E-9) { // cos(beta_local) == 1.0
                   cosc = wind_local_Y(eY);
 
                   if (fabs(cosacosb) > fabs(sinacosb))
                     sinc = wind_local_Y(eZ) / cosacosb;
                   else
                     sinc = -wind_local_Y(eX) / sinacosb;
                 }
                 else if (fabs(fabs(sinb)-1.0) < 1E-9) { // cos(beta_local) == 0.0
                   sinc = wind_local_Y(eZ);
                   cosc = -wind_local_Y(eX);
                 }
                 else {
                   sinc = cosacosb*wind_local_Y(eZ)-sinacosb*wind_local_Y(eX);
                   cosc = (-sinacosb*wind_local_Y(eZ)-cosacosb*wind_local_Y(eX))/sinb;
                 }
 
                 return atan2(sinc, cosc)*radtodeg;
               };
      Parameters.push_back(new aFunc<decltype(f), 6>(f, fdmex, element, Prefix, var));
    } else if (operation == "rotation_bf_to_wf") {
      // Transforms the input vector from a body frame to a wind frame. The
      // origin of the vector remains the same.
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& p)->double {
                 double rx = p[0]->GetValue();             //x component of input vector
                 double ry = p[1]->GetValue();             //y component of input vector
                 double rz = p[2]->GetValue();             //z component of input vector
                 double alpha = p[3]->GetValue()*degtorad; //angle of attack of the body frame
                 double beta = p[4]->GetValue()*degtorad;  //sideslip angle of the body frame
                 double gamma = p[5]->GetValue()*degtorad; //roll angle of the body frame
                 int idx = static_cast<int>(p[6]->GetValue());
 
                 if ((idx < 1) || (idx > 3)) {
                   cerr << ctxMsg << fgred << highint
                        << "The index must be one of the integer value 1, 2 or 3."
                        << reset << endl;
                   throw BaseException("Fatal error");
                 }
 
                 FGQuaternion qa(eY, -alpha), qb(eZ, beta), qc(eX, -gamma);
                 FGMatrix33 mT = (qa*qb*qc).GetT();
                 FGColumnVector3 r0(rx, ry, rz);
                 FGColumnVector3 r = mT*r0;
 
                 return r(idx);
               };
      Parameters.push_back(new aFunc<decltype(f), 7>(f, fdmex, element, Prefix, var));
    } else if (operation == "rotation_wf_to_bf") {
      // Transforms the input vector from q wind frame to a body frame. The
      // origin of the vector remains the same.
      string ctxMsg = element->ReadFrom();
      auto f = [ctxMsg](const decltype(Parameters)& p)->double {
                 double rx = p[0]->GetValue();             //x component of input vector
                 double ry = p[1]->GetValue();             //y component of input vector
                 double rz = p[2]->GetValue();             //z component of input vector
                 double alpha = p[3]->GetValue()*degtorad; //angle of attack of the body frame
                 double beta = p[4]->GetValue()*degtorad;  //sideslip angle of the body frame
                 double gamma = p[5]->GetValue()*degtorad; //roll angle of the body frame
                 int idx = static_cast<int>(p[6]->GetValue());
 
                 if ((idx < 1) || (idx > 3)) {
                   cerr << ctxMsg << fgred << highint
                        << "The index must be one of the integer value 1, 2 or 3."
                        << reset << endl;
                   throw BaseException("Fatal error");
                 }
 
                 FGQuaternion qa(eY, -alpha), qb(eZ, beta), qc(eX, -gamma);
                 FGMatrix33 mT = (qa*qb*qc).GetT();
                 FGColumnVector3 r0(rx, ry, rz);
                 mT.T();
                 FGColumnVector3 r = mT*r0;
 
                 return r(idx);
               };
      Parameters.push_back(new aFunc<decltype(f), 7>(f, fdmex, element, Prefix, var));
    } else if (operation != "description") {
      cerr << element->ReadFrom() << fgred << highint
           << "Bad operation <" << operation
           << "> detected in configuration file" << reset << endl;
    }
 
    // Optimize functions applied on constant parameters by replacing them by
    // their constant result.
    if (!Parameters.empty()){
      FGFunction* p = dynamic_cast<FGFunction*>(Parameters.back().ptr());
 
      if (p && p->IsConstant()) {
        double constant = p->GetValue();
        FGPropertyNode_ptr node = p->pNode;
        string pName = p->GetName();
 
        Parameters.pop_back();
        Parameters.push_back(new FGRealValue(constant));
        if (debug_lvl > 0)
          cout << element->ReadFrom() << fggreen << highint
               << "<" << operation << "> is applied on constant parameters."
               << endl << "It will be replaced by its result ("
               << constant << ")";
 
        if (node) {
          node->setDoubleValue(constant);
          node->setAttribute(SGPropertyNode::WRITE, false);
          if (debug_lvl > 0)
            cout << " and the property " << pName
                 << " will be unbound and made read only.";
        }
        cout << reset << endl << endl;
      }
    }
    element = el->GetNextElement();
  }
 
  bind(el, Prefix); // Allow any function to save its value
 
  Debug(0);
}

Member Data Documentation

cached

bool cached

protected

Definition at line 828 of file FGFunction.h.

cachedValue

double cachedValue

protected

Definition at line 829 of file FGFunction.h.

Parameters

std::vector<FGParameter_ptr> Parameters

protected

Definition at line 830 of file FGFunction.h.

pNode

FGPropertyNode_ptr pNode

protected

Definition at line 832 of file FGFunction.h.

PropertyManager

std::shared_ptr<FGPropertyManager> PropertyManager

protected

Definition at line 831 of file FGFunction.h.

---

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

• FGFunction.h
• FGFunction.cpp