Represents part of a grammar for the LLParserGenerator. More...
Source files:
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 | |
| 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, 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] |
Public Member Functions | |
| 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... | |
| abstract void | Call (PredVisitor visitor) |
| Public Member Functions inherited from Loyc.ICloneable< Pred > | |
| T | Clone () |
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
◆ 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().
◆ 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 in Loyc.LLParserGenerator.AndPred, Loyc.LLParserGenerator.Gate, Loyc.LLParserGenerator.Alts, and Loyc.LLParserGenerator.Seq.
Referenced by Loyc.LLParserGenerator.Seq.Clone(), Loyc.LLParserGenerator.Gate.Clone(), and Loyc.LLParserGenerator.AndPred.Clone().
Member Data Documentation
◆ 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
◆ IsNullable
|
get |
Returns true if this predicate can match an empty input.
