Represents a symbol, which is a singleton string that supports fast comparisons and extensible enums. More...

Source file:

/Core/Loyc.Interfaces/Concrete/Symbol.cs

Inheritance diagram for Loyc.Symbol:

Remarks

Represents a symbol, which is a singleton string that supports fast comparisons and extensible enums.

Call GSymbol.Get() to create a Symbol from a string, or GSymbol.GetIfExists() to find a Symbol that has already been created.

Symbols can be used like a global, extensible enumeration. Comparing symbols is as fast as comparing two integers; this is because '==' is not overloaded–equality is defined as reference equality, as there is only one instance of a given Symbol.

Symbols can also be produced in namespaces called "pools". Two Symbols with the same name, but in different pools, are considered to be different symbols. Using a derived class D of Symbol and a SymbolPool<D>, you can make Symbols that are as type-safe as enums.

A Symbol's ToString() function formerly returned the symbol name prefixed with a colon (:), following the convention of the Ruby language, from which I got the idea of Symbols in the first place. However, since Symbols are commonly used for extensible enums, I decided it was better that ToString() return just the Name alone, which makes Symbol more suitable as a drop-in replacement for enums.

Symbols are also useful in compilers and Loyc trees, where there may be a performance advantage in comparing identifiers by reference rather than character-by-character.

Properties
string	Name `[get]`
	Gets the name of the Symbol. More...

SymbolPool	Pool `[get]`
	Gets the SymbolPool in which this Symbol was created. More...

bool	IsGlobal `[get]`
	Returns true if this symbol is in the global pool (GSymbol.Pool). More...

int	Id `[get]`
	Returns a numeric ID for the Symbol. More...

Public Member Functions
override string	ToString ()

override int	GetHashCode ()

override bool	Equals (object b)

bool	Equals (Symbol b)

int	CompareTo (Symbol other)

Static Public Member Functions
static	operator Symbol (string s)

static	operator string (Symbol s)

static	operator Symbol (UString s)

static	operator UString (Symbol s)

static Symbol	For (string s)
	Alias for GSymbol.Get(string). This function was introduced to match the equivalent ES6 API `Symbol.for("string")` More...

Protected Member Functions
	Symbol (Symbol prototype)
	For use by a derived class to produce a statically-typed enumeration in a private pool. See the example under SymbolPool (of SymbolEnum) More...

Constructor & Destructor Documentation

◆ Symbol()

Loyc.Symbol.Symbol ( Symbol prototype )

inlineprotected

For use by a derived class to produce a statically-typed enumeration in a private pool. See the example under SymbolPool (of SymbolEnum)

Parameters

prototype A strictly temporary Symbol that is used to initialize this object. The derived class should discard the prototype after calling this constructor.

Member Function Documentation

◆ For()

static Symbol Loyc.Symbol.For ( string s )

inlinestatic

Alias for GSymbol.Get(string). This function was introduced to match the equivalent ES6 API Symbol.for("string")

Property Documentation

◆ Id

int Loyc.Symbol.Id

get

Returns a numeric ID for the Symbol.

Normally the Id is auto-assigned and the Id corresponding to a particular Name may vary between different runs of the same program. However, SymbolPool.Get(string, int) can be used to assign a specific Id to a Name when setting up a new pool.

◆ IsGlobal

bool Loyc.Symbol.IsGlobal

get

Returns true if this symbol is in the global pool (GSymbol.Pool).

◆ Name

string Loyc.Symbol.Name

get

Gets the name of the Symbol.

Referenced by Loyc.Syntax.CallNode.CallsMin(), Loyc.LLParserGenerator.RuleRef.ChooseGotoLabel(), Loyc.LLParserGenerator.CodeGenHelperBase.ErrorBranch(), Loyc.LLPG.Macros.LLLPG_lexer(), Loyc.LLPG.Macros.LLLPG_parser(), Loyc.Localize.Passthrough(), Loyc.Syntax.Les.Les2PrecedenceMap.ResemblesSuffixOperator(), Loyc.Syntax.LiteralHandlerTable.TryParse(), and Loyc.Localize.UseResourceManager().

◆ Pool

SymbolPool Loyc.Symbol.Pool

get

Gets the SymbolPool in which this Symbol was created.