vita::symbol Class Reference

Together functions and terminals are referred to as symbols. More...

#include <symbol.h>

Inherited by vita::function, and vita::terminal.

Public Types
enum	format {   c_format , cpp_format , mql_format , python_format ,   sup_format }
	Symbol rendering format. More...

Public Member Functions
virtual unsigned	arity () const =0
category_t	category () const
	The type (a.k.a. More...
void	category (category_t)
	Changes the category of a symbol. More...
virtual value_t	eval (symbol_params &) const =0
	Calculates the value of / performs the action associated with the symbol (it's implementation specific). More...
virtual bool	input () const
	An input variable is a feature from the learning domain. More...
virtual bool	is_valid () const
std::string	name () const
opcode_t	opcode () const
	An opcode is a unique, numerical session ID for a symbol. More...
double	penalty (core_interpreter *) const
	Used for automatic calculation of penalities due to broken constraints. More...
	symbol (const std::string &, category_t=0)
bool	terminal () const

Detailed Description

Together functions and terminals are referred to as symbols.

GP assembles variable length program structures from basic units called functions and terminals. Functions perform operations on their inputs, which are either terminals or output from other functions.

Definition at line 35 of file symbol.h.

Member Enumeration Documentation

format

enum vita::symbol::format

Symbol rendering format.

Definition at line 39 of file symbol.h.

Constructor & Destructor Documentation

symbol()

vita::symbol::symbol ( const std::string &  name, category_t  c = 0  )

explicit

Parameters

[in]	name	name of the symbol
[in]	c	category of the symbol

Note

By default a symbol:

• is NOT associative;
• is NOT an input;
• is NOT parametric. These are safe values for derived classes.

Warning

Since the name of the symbol is used for serialization, it must be unique. Even the opcode is unique, but it can change between executions.

Definition at line 35 of file symbol.cc.

Member Function Documentation

arity()

virtual unsigned vita::symbol::arity ( ) const

pure virtual

Implemented in vita::function, and vita::terminal.

category() [1/2]

category_t vita::symbol::category ( ) const

inline

The type (a.k.a.

category) of the symbol

Returns

the category

In strongly typed GP every terminal and every function argument / return value has a type (a.k.a. category).

Definition at line 99 of file symbol.h.

category() [2/2]

void vita::symbol::category ( category_t  c )

inline

Changes the category of a symbol.

Parameters

[in]

c

the new category

Remarks

Should be called only for symbols with undefined category.

Definition at line 111 of file symbol.h.

eval()

virtual value_t vita::symbol::eval ( symbol_params &  ) const

pure virtual

Calculates the value of / performs the action associated with the symbol (it's implementation specific).

Implemented in vita::boolean::zero, vita::boolean::one, vita::constant< T >, vita::constant< std::string >, vita::boolean::l_and, vita::boolean::l_not, vita::boolean::l_or, vita::integer::add, vita::integer::div, vita::integer::ife, vita::integer::ifl, vita::integer::ifz, vita::integer::mod, vita::integer::mul, vita::integer::shl, vita::integer::sub, vita::real::abs, vita::real::add, vita::real::aq, vita::real::cos, vita::real::div, vita::real::gt, vita::real::idiv, vita::real::ifb, vita::real::ife, vita::real::ifl, vita::real::ifz, vita::real::length, vita::real::ln, vita::real::lt, vita::real::max, vita::real::mod, vita::real::mul, vita::real::sin, vita::real::sqrt, vita::real::sub, vita::real::sigmoid, vita::str::ife, vita::integer::number, vita::real::real, vita::real::integer, and vita::variable.

Examples

example6.cc.

input()

bool vita::symbol::input ( ) const

inlinevirtual

An input variable is a feature from the learning domain.

Returns

true if the symbol is an input variable

Only a terminal can be an input variable.

Default (safe) value is false.

Reimplemented in vita::variable.

Examples

example6.cc.

Definition at line 128 of file symbol.h.

is_valid()

bool vita::symbol::is_valid ( ) const

virtual

Returns

true if the object passes the internal consistency check

Reimplemented in vita::function.

Definition at line 60 of file symbol.cc.

name()

std::string vita::symbol::name

(

)

const

Returns

the name of the symbol

Definition at line 44 of file symbol.cc.

opcode()

opcode_t vita::symbol::opcode ( ) const

inline

An opcode is a unique, numerical session ID for a symbol.

Returns

the opcode

The opcode is a fast way to uniquely identify a symbol and is primarily used for hashing.

Remarks

A symbol can be identified also by its name (a std::string). The name is often a better option since it doesn't change among executions.

Definition at line 145 of file symbol.h.

penalty()

double vita::symbol::penalty ( core_interpreter *  ci ) const

inline

Used for automatic calculation of penalities due to broken constraints.

Parameters

[in]

ci

interpreter used for symbol's constraints evaluation

Returns

a penalty based on symbol specific broken constraints

• 0.0 states that no constraint penalty is applied;
• larger values specify larger penalties.

Definition at line 86 of file symbol.h.

terminal()

bool vita::symbol::terminal ( ) const

inline

Returns

true if this symbol is a terminal

Definition at line 153 of file symbol.h.

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

• symbol.h
• symbol.cc