MUSHclient documentation: lpeg.V

lpeg.V

lpeg.V
Lua function lpeg.V Summary Creates a non-terminal variable for a grammar Prototype `lpeg.V (v)` Description This operation creates a non-terminal (a variable) for a grammar. The created non-terminal refers to the rule indexed by v in the enclosing grammar. The call lpeg.V(v) creates a pattern that represents the nonterminal (or variable) with index v in a grammar. Because the grammar still does not exist when this function is evaluated, the result is an open reference to the respective rule. A table is fixed when it is converted to a pattern (either by calling lpeg.P or by using it wherein a pattern is expected). Then every open reference created by lpeg.V(v) is corrected to refer to the rule indexed by v in the table. For example: -- Grammar local Exp, Term, Factor = lpeg.V"Exp", lpeg.V"Term", lpeg.V"Factor" G = lpeg.P{ Exp, Exp = lpeg.Ct(Factor * (FactorOp * Factor)^0); Factor = lpeg.Ct(Term * (TermOp * Term)^0); Term = Number + Open * Exp * Close; } See Also ... Topics Lua bc (big number) functions Lua bit manipulation functions Lua LPEG library Lua package functions Lua PCRE regular expression functions Lua script extensions Lua string functions Lua table functions Lua utilities Regular Expressions Scripting Lua functions lpeg.C (Creates a simple capture) lpeg.Carg (Creates an argument capture) lpeg.Cb (Creates a back capture) lpeg.Cc (Creates a constant capture) lpeg.Cf (Creates a fold capture) lpeg.Cg (Creates a group capture) lpeg.Cmt (Creates a match-time capture) lpeg.Cp (Creates a position capture) lpeg.Cs (Creates a substitution capture) lpeg.Ct (Creates a table capture) lpeg.locale (Returns a table of patterns matching the current locale) lpeg.match (Matches a pattern against a string) lpeg.P (Converts a value into a pattern) lpeg.print (Outputs debugging information to stdout) lpeg.R (Returns a pattern that matches a range of characters) lpeg.S (Returns a pattern that matches a set of characters) lpeg.type (Tests if a value is a pattern) lpeg.version (Returns the LPeg version) (Help topic: lua=lpeg.V) Documentation contents page

Lua function

lpeg.V

Summary

Creates a non-terminal variable for a grammar

Prototype

lpeg.V (v)

Description

This operation creates a non-terminal (a variable) for a grammar. The created non-terminal refers to the rule indexed by v in the enclosing grammar. 



The call lpeg.V(v) creates a pattern that represents the nonterminal (or variable) with index v in a grammar. Because the grammar still does not exist when this function is evaluated, the result is an open reference to the respective rule.



A table is *fixed* when it is converted to a pattern (either by calling lpeg.P or by using it wherein a pattern is expected). Then every open reference created by lpeg.V(v) is corrected to refer to the rule indexed by v in the table.



For example:



-- Grammar

local Exp, Term, Factor = lpeg.V"Exp", lpeg.V"Term", lpeg.V"Factor"

G = lpeg.P{ Exp,

  Exp = lpeg.Ct(Factor * (FactorOp * Factor)^0);

  Factor = lpeg.Ct(Term * (TermOp * Term)^0);

  Term = Number + Open * Exp * Close;

}