lpeg.V
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;
}
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;
}
Lua functions
- lpeg.B - Matches patt n characters behind the current position, consuming no input
- 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.setmaxstack - Sets the maximum size for the backtrack stack
- lpeg.type - Tests if a value is a pattern
- lpeg.version - Returns the LPeg version