ultra::symbol Class Reference

#include <symbol.h>

Inheritance diagram for ultra::symbol:

Public Types
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
	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
virtual std::string	to_string (format=c_format) const =0
void	category (category_t) noexcept
virtual bool	is_valid () const

Static Public Attributes
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

Base class for all symbols.

In ULTRA, symbols are the atomic building blocks from which programs are constructed. Together, functions (internal nodes) and terminals (leaf nodes) form the symbol set used by the evolutionary algorithm to assemble executable program structures.

A symbol is uniquely identified across runs by its name. Symbols may also belong to a category, which is used to enforce strong typing in GP and to manage value domains in GA / DE contexts.

Note

Symbols are immutable with respect to their identity (name and opcode). The category may be assigned after construction only if initially marked as undefined.

Member Typedef Documentation

category_t

using ultra::symbol::category_t = unsigned

Type used to represent symbol categories.

Categories are used to:

• enforce strong typing in genetic programming;
• define admissible value ranges in genetic algorithms and differential evolution.

A category represents a sub-domain of values. The same numerical value may belong to different categories (e.g. "kg" vs "km/h").

opcode_t

using ultra::symbol::opcode_t = unsigned

Type used as a fast, session-local identifier for symbols.

Opcodes are unique within a single execution and are primarily used for hashing and fast comparisons. They are not stable across executions and must not be serialised.

Constructor & Destructor Documentation

symbol()

ultra::symbol::symbol ( const std::string & name, category_t c = default_category )

explicit

Constructs a symbol with the given name and category.

Parameters

[in]	name	name of the symbol (unique textual identifier)
[in]	c	category of the symbol

Warning

The symbol name is used for serialisation and must be globally unique within a symbol set. While opcodes are also unique, they are assigned dynamically and may differ between executions.

Member Function Documentation

category() [1/2]

symbol::category_t ultra::symbol::category ( ) const

nodiscardnoexcept

Returns the category of the symbol.

Returns

category associated with the symbol

category() [2/2]

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

noexcept

Assigns a category to the symbol.

Parameters

[in]

c

new category value

Precondition

The current category must be undefined_category

Remarks

This function exists to support deferred category assignment. It should not be used to change an already defined category.

is_valid()

bool ultra::symbol::is_valid ( ) const

nodiscardvirtual

Performs an internal consistency check.

Returns

true if the symbol satisfies basic validity constraints

Remarks

Derived classes are expected to extend this check to enforce additional invariants.

Reimplemented in ultra::function.

name()

const std::string & ultra::symbol::name ( ) const

nodiscardnoexcept

Returns the name of the symbol.

Returns

constant reference to the symbol name

Note

The name uniquely identifies the symbol across executions and is used during serialisation.

opcode()

symbol::opcode_t ultra::symbol::opcode ( ) const

nodiscardnoexcept

Returns the opcode of the symbol.

Returns

a session-local, unique numerical identifier

Note

The opcode is intended for fast internal use (e.g. hashing). It is not stable across executions and must not be used for persistence.

to_string()

virtual std::string ultra::symbol::to_string ( format = c_format ) const

nodiscardpure virtual

Implemented in ultra::function, 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.

Member Data Documentation

undefined_category

category_t ultra::symbol::undefined_category

staticconstexpr

Initial value:

=
    std::numeric_limits<category_t>::max()

Sentinel value indicating that the category has not yet been assigned.

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

• symbol.h
• symbol.cc