ultra::function Class Reference

#include <function.h>

Inheritance diagram for ultra::function:

Classes
class	params

Public Types
using	param_data_types = std::vector<category_t>
using	return_type = category_t
	Type used to describe the return category of the function.
Public Types inherited from ultra::symbol
enum	format { c_format , cpp_format , python_format , sup_format }
	Supported rendering formats for symbol stringification.
using	category_t = unsigned
using	opcode_t = unsigned

Public Member Functions
	function (const std::string &, return_type, param_data_types)
	function (const std::string &, std::size_t)
category_t	param_category (std::size_t) const noexcept
const param_data_types &	categories () const noexcept
std::size_t	arity () const noexcept
virtual value_t	eval (const params &) const =0
virtual std::string	to_string (format=c_format) const override
bool	is_valid () const override
Public Member Functions inherited from ultra::symbol
	symbol (const std::string &, category_t=default_category)
virtual	~symbol ()=default
	Virtual destructor to allow safe polymorphic deletion.
category_t	category () const noexcept
opcode_t	opcode () const noexcept
const std::string &	name () const noexcept
void	category (category_t) noexcept

Additional Inherited Members
Static Public Attributes inherited from ultra::symbol
static constexpr category_t	default_category = 0
	Default category assigned when typing is not used.
static constexpr category_t	undefined_category
	Sentinel value indicating that the category has not yet been assigned.

Detailed Description

A callable GP symbol with one or more input parameters.

In ULTRA, a function represents a non-terminal symbol in a genetic programming "tree". Functions label internal nodes and are evaluated by recursively evaluating their arguments and combining the results.

Each function has:

• a return category (inherited from symbol);
• a fixed arity;
• a category for each input parameter.

Categories are used to enforce strong typing constraints during program construction, mutation, and crossover.

Note

Functions must satisfy the closure property: they must be able to handle any input values that conform to their parameter categories without causing undefined behaviour or runtime errors.

Member Typedef Documentation

param_data_types

using ultra::function::param_data_types = std::vector<category_t>

Type used to describe the categories of input parameters.

The size of this container defines the arity of the function.

Constructor & Destructor Documentation

function() [1/2]

ultra::function::function	(	const std::string &	name,
		return_type	r,
		param_data_types	par )

Constructs a typed function.

Parameters

[in]	name	string representation of the function (e.g. "ADD", "+")
[in]	r	return category of the function
[in]	par	categories of the input parameters

This constructor is typically used in strongly typed GP, where both argument and return categories are explicitly specified.

function() [2/2]

ultra::function::function	(	const std::string &	name,
		std::size_t	n_pars )

Constructs an untyped function with the given arity.

Parameters

[in]	name	string representation of the function
[in]	n_pars	number of input parameters

Remarks

The function and all its parameters are assigned symbol::default_category. This constructor is intended for GP configurations where strong typing is not used.

Member Function Documentation

arity()

std::size_t ultra::function::arity ( ) const

nodiscardnoexcept

Returns the number of input parameters of the function.

Returns

function arity

categories()

const function::param_data_types & ultra::function::categories ( ) const

nodiscardnoexcept

Returns the list of input parameter categories.

Returns

constant reference to the parameter category list

Remarks

The size of the returned container is equal to the function arity.

eval()

virtual value_t ultra::function::eval ( const params & ) const

pure virtual

Evaluates the function for the given parameters.

Returns

result of the function evaluation

Remarks

Parameters are accessed via the params interface, which supports lazy evaluation and optional referential transparency. Implementations should avoid fetching arguments multiple times unless necessary.

Warning

Implementations must not assume any particular evaluation order of parameters.

Implemented in ultra::integer::add, ultra::integer::div, ultra::integer::ife, ultra::integer::ifl, ultra::integer::ifz, ultra::integer::mod, ultra::integer::mul, ultra::integer::shl, ultra::integer::sub, ultra::real::abs, ultra::real::add, ultra::real::aq, ultra::real::cos, ultra::real::div, ultra::real::exp, ultra::real::gt, ultra::real::idiv, ultra::real::ife, ultra::real::ifl, ultra::real::ifz, ultra::real::length, ultra::real::ln, ultra::real::lt, ultra::real::max, ultra::real::mod, ultra::real::mul, ultra::real::sigmoid, ultra::real::sin, ultra::real::sqrt, ultra::real::sub, and ultra::str::ife.

is_valid()

bool ultra::function::is_valid ( ) const

nodiscardoverridevirtual

Performs an internal consistency check.

Returns

true if the function satisfies basic validity constraints

Reimplemented from ultra::symbol.

param_category()

symbol::category_t ultra::function::param_category ( std::size_t i ) const

nodiscardnoexcept

Returns the category of a specific input parameter.

Parameters

[in]

i

index of the input parameter

Returns

category of the i-th parameter

Precondition

i < arity()

to_string()

std::string ultra::function::to_string ( format = c_format ) const

nodiscardoverridevirtual

Returns a string representation of the function.

Remarks

The base implementation produces a generic functional notation (e.g. ADD({0},{1})). Derived classes may override this method to support alternative syntaxes or formatting conventions.

Note

Format templates should not contain unbalanced parentheses inside comments or string literals, as program rendering checks enclosing parentheses directly on the template.

Returns

the name of the function

Warning

Specific functions have to specialize this method to support different output formats. Format templates should avoid unbalanced parentheses in comments or string literals.

Implements ultra::symbol.

Reimplemented in ultra::integer::add, ultra::integer::div, ultra::integer::ife, ultra::integer::ifl, ultra::integer::ifz, ultra::integer::mod, ultra::integer::mul, ultra::integer::shl, ultra::integer::sub, ultra::real::abs, ultra::real::add, ultra::real::aq, ultra::real::cos, ultra::real::div, ultra::real::exp, ultra::real::gt, ultra::real::idiv, ultra::real::ife, ultra::real::ifl, ultra::real::ifz, ultra::real::length, ultra::real::ln, ultra::real::lt, ultra::real::max, ultra::real::mod, ultra::real::mul, ultra::real::sigmoid, ultra::real::sin, ultra::real::sqrt, ultra::real::sub, and ultra::str::ife.

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

• function.h
• function.cc