Loyc.LLParserGenerator.Pred Class Reference

Represents part of a grammar for the LLParserGenerator. More...

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Source file:

• /Main/LLLPG/RuleAndPreds/Predicates.cs

Inheritance diagram for Loyc.LLParserGenerator.Pred:

Remarks

Represents part of a grammar for the LLParserGenerator.

This class is the root of a class hierarchy which contains

• TerminalPred: represents a terminal (which is a token or a character) or a set of possible terminals (e.g. 'A'..'Z').
• RuleRef: represents a nonterminal, which is a reference to a rule.
• Other components of a rule: sequences (Seq), branches and loops (Alts), gates (Gate, a mechanism to separate prediction from matching), and and-predicates (AndPred, an assertion that consumes no input).
• EndOfRule: a container for the follow set of a Rule (this class is not a real predicate; it is derived from Pred so that it can be a legal value for Pred.Next).

Each Pred object can be used only once in a grammar, because Preds contain context- sensitive state such as the Next field, which are used during grammar analysis. A Pred must be Clone()d if one wants to use it multiple times.

Public fields
LNode	PreAction
LNode	PostAction
Symbol	VarLabel
bool	VarIsList
Func< LNode, LNode >	ResultSaver
	A function that saves the result produced by the matching code of this predicate (null if the result is not saved). For example, if the parser generator is given the predicate @[ x='a'..'z' ], the default matching code will be @(Match('a', 'z')), and ResultSaver will be set to a function that receives this matching code and returns @(x = Match('a', 'z')) in response. More...

Properties
LNode	Basis [get, set]
abstract bool	IsNullable [get]
	Returns true if this predicate can match an empty input. More...
object	Location [get]
Properties inherited from Loyc.IHasLocation
object	Location [get]

Public Member Functions
abstract void	Call (PredVisitor visitor)
	Pred (LNode basis)
LNode	AutoSaveResult (LNode matchingCode)
virtual Pred	Clone ()
	Deep-clones a predicate tree. Terminal sets and Nodes referenced by the tree are not cloned; the clone's value of Next will be null. The same Pred cannot appear in two places in a tree, so you must clone before re-use. More...
string	ToStringWithPosition ()
virtual string	ChooseGotoLabel ()
	Optional. If this predicate represents the matching code for a branch of an Alts and this code is reached through a goto statement, this method is used to select a label name. Supported by RuleRef. More...

Static Public Member Functions
static Seq	operator+ (char a, Pred b)
static Seq	operator+ (Pred a, char b)
static Seq	operator+ (Pred a, Pred b)
static Pred	operator| (char a, Pred b)
static Pred	operator| (Pred a, char b)
static Pred	operator| (Pred a, Pred b)
static Pred	operator/ (Pred a, Pred b)
static Pred	operator+ (Pred a)
static Pred	Or (Pred a, Pred b, bool slashJoined)
static Pred	Or (Pred a, Pred b, bool slashJoined, LNode basis, BranchMode aMode=BranchMode.None, BranchMode bMode=BranchMode.None, IMessageSink sink=null)
static Alts	Star (Pred contents, bool?greedy=null)
static Alts	Opt (Pred contents, bool?greedy=null)
static Seq	Plus (Pred contents, bool?greedy=null)
static TerminalPred	Range (char lo, char hi)
static TerminalPred	Set (IPGTerminalSet set)
static TerminalPred	Set (string set)
static TerminalPred	Set (params LNode[] s)
static TerminalPred	Not (params LNode[] s)
static TerminalPred	Char (char c)
static TerminalPred	Chars (params char[] c)
static Seq	Seq (string s, LNode basis=null)
static Rule	Rule (string name, Pred pred, bool isStartingRule=false, bool isToken=false, int maximumK=-1)
static Pred	operator+ (LNode pre, Pred p)
static Pred	operator+ (Pred p, LNode post)
static LNode	MergeActions (LNode action, LNode action2)
static AndPred	And (object test)
static AndPred	AndNot (object test)
static Pred	Set (string varName, Pred pred)
static Pred	SetVar (string varName, Pred pred)
static Pred	AddSet (string varName, Pred pred)
static Pred	Op (string varName, Symbol @operator, Pred pred)

Member Function Documentation

virtual string Loyc.LLParserGenerator.Pred.ChooseGotoLabel ( )

inlinevirtual

Optional. If this predicate represents the matching code for a branch of an Alts and this code is reached through a goto statement, this method is used to select a label name. Supported by RuleRef.

Returns

A label name, or null if the predicate did not choose one.

Reimplemented in Loyc.LLParserGenerator.Seq, and Loyc.LLParserGenerator.RuleRef.

Referenced by Loyc.LLParserGenerator.Seq.ChooseGotoLabel().

virtual Pred Loyc.LLParserGenerator.Pred.Clone ( )

inlinevirtual

Deep-clones a predicate tree. Terminal sets and Nodes referenced by the tree are not cloned; the clone's value of Next will be null. The same Pred cannot appear in two places in a tree, so you must clone before re-use.

Implements Loyc.ICloneable< out T >.

Reimplemented in Loyc.LLParserGenerator.AndPred, Loyc.LLParserGenerator.Gate, Loyc.LLParserGenerator.Alts, and Loyc.LLParserGenerator.Seq.

Member Data Documentation

Func<LNode, LNode> Loyc.LLParserGenerator.Pred.ResultSaver

A function that saves the result produced by the matching code of this predicate (null if the result is not saved). For example, if the parser generator is given the predicate @[ x='a'..'z' ], the default matching code will be @(Match('a', 'z')), and ResultSaver will be set to a function that receives this matching code and returns @(x = Match('a', 'z')) in response.

Property Documentation

abstract bool Loyc.LLParserGenerator.Pred.IsNullable

get

Returns true if this predicate can match an empty input.