Represents a "gate" (p => m), which is a mechanism to separate prediction from matching in the context of branching (Alts). More...
Source files:
Remarks
Represents a "gate" (p => m), which is a mechanism to separate prediction from matching in the context of branching (Alts).
Gates are explained futher in this article: http://www.codeproject.com/Articles/688152/The-Loyc-LL-k-Parser-Generator-Part-2
Public fields | |
| Pred | Predictor |
| Left-hand side of the gate, which is used for prediction decisions. More... | |
| Pred | Match |
| Right-hand side of the gate, which is used for matching decisions. More... | |
 Public fields inherited from Loyc.LLParserGenerator.Pred | |
| 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... | |
Public Member Functions | |
| Gate (LNode basis, Pred predictor, Pred match) | |
| override void | Call (PredVisitor visitor) |
| Public Member Functions inherited from Loyc.LLParserGenerator.Pred | |
| Pred (LNode basis) | |
| LNode | AutoSaveResult (LNode matchingCode) |
| 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... | |
| Public Member Functions inherited from Loyc.ICloneable< Pred > | |
| T | Clone () |
| bool | IsEquivalency [get, set] |
| If true, this is an "<=>" equivalency gate, otherwise it's a "=>" normal gate. More... | |
| override bool | IsNullable [get] |
| override 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... | |
| override string | ToString () |
Additional Inherited Members | |
| Properties inherited from Loyc.LLParserGenerator.Pred | |
| LNode | Basis [get, protected 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] |
| Static Public Member Functions inherited from Loyc.LLParserGenerator.Pred | |
| 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
◆ 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.
Reimplemented from Loyc.LLParserGenerator.Pred.
References Loyc.LLParserGenerator.Pred.Clone(), Loyc.LLParserGenerator.Gate.Clone(), Loyc.LLParserGenerator.Gate.Match, and Loyc.LLParserGenerator.Gate.Predictor.
Referenced by Loyc.LLParserGenerator.Gate.Clone().
Member Data Documentation
◆ Match
| Pred Loyc.LLParserGenerator.Gate.Match |
Right-hand side of the gate, which is used for matching decisions.
Referenced by Loyc.LLParserGenerator.Gate.Clone().
◆ Predictor
| Pred Loyc.LLParserGenerator.Gate.Predictor |
Left-hand side of the gate, which is used for prediction decisions.
Referenced by Loyc.LLParserGenerator.Gate.Clone().
Property Documentation
◆ IsEquivalency
|
getset |
If true, this is an "<=>" equivalency gate, otherwise it's a "=>" normal gate.
This controls the follow set of the predictor. For a "=>" normal gate, the predictor (left-hand side) has anything (_*) as its follow set. For an equivalency, in which the predictor side and the match side are intended to represent the same language, the follow set of the predictor will be the same as that of the match; both are set to whatever follows the gate as a whole.
The "=>" normal gate is often used to simplify or tweak prediction decisions, e.g. in this example the gate is intended to ensure that the caller will not call Number unless LA0 is ('.'|'0'..'9'):
Notice that the predictor is, in general, shorter than the match side. It could potentially confuse the caller if the follow set of the predictor and match sides were the same. An equivalency gate, on the other hand, should be the same length as the match side, so it can have the same follow set (I don't have a use case in mind for an equivalency gate yet).
