Package org.antlr.v4.automata
Interface ATNFactory
- All Known Implementing Classes:
LexerATNFactory
,ParserATNFactory
public interface ATNFactory
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Nested Class Summary
Nested ClassesModifier and TypeInterfaceDescriptionstatic class
A pair of states pointing to the left/right (start and end) states of a state submachine. -
Method Summary
Modifier and TypeMethodDescriptionBuild what amounts to an epsilon transition with an action.alt
(List<ATNFactory.Handle> els) block
(BlockAST blockAST, GrammarAST ebnfRoot, List<ATNFactory.Handle> alternativeGrips) From A|B|..|Z alternative block build o->o-A->o->o (last ATNState is blockEndATNState pointed to by all alts) | ^ o->o-B->o--| | | ...charSetLiteral
(GrammarAST charSetAST) epsilon
(GrammarAST node) From an empty alternative build Grip o-e->olexerAltCommands
(ATNFactory.Handle alt, ATNFactory.Handle cmds) lexerCallCommand
(GrammarAST ID, GrammarAST arg) newState()
optional
(GrammarAST optAST, ATNFactory.Handle blk) From (A)? build either: o--A->o | ^ o---->| or, if A is a block, just add an empty alt to the end of the blockplus
(GrammarAST plusAST, ATNFactory.Handle blk) From (A)+ build |---| (Transition 2 from A.right points at alt 1) v | (follow of loop is Transition 1) o->o-A-o->o Meaning that the last ATNState in A points back to A's left Transition ATNState and we add a new begin/end ATNState.range
(GrammarAST a, GrammarAST b) rule
(GrammarAST ruleAST, String name, ATNFactory.Handle blk) ruleRef
(GrammarAST node) For reference to rule r, build o-e->(r) o where (r) is the start of rule r and the trailing o is not linked to from rule ref state directly (it's done thru the transition(0) RuleClosureTransition.Build what amounts to an epsilon transition with a semantic predicate action.set
(GrammarAST associatedAST, List<GrammarAST> alts, boolean invert) void
setCurrentOuterAlt
(int alt) void
setCurrentRuleName
(String name) star
(GrammarAST starAST, ATNFactory.Handle blk) From (A)* build |---| v | o->o-A-o--o (Transition 2 from block end points at alt 1; follow is Transition 1) | ^ o---------| (optional branch is 2nd alt of optional block containing A+) Meaning that the last (end) ATNState in A points back to A's left side ATNState and we add 3 new ATNStates (the optional branch is built just like an optional subrule).stringLiteral
(TerminalAST stringLiteralAST) For a non-lexer, just build a simple token reference atom.tokenRef
(TerminalAST node) wildcard
(GrammarAST associatedAST) Build an atom with all possible values in its label
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Method Details
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createATN
ATN createATN() -
setCurrentRuleName
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setCurrentOuterAlt
void setCurrentOuterAlt(int alt) -
rule
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newState
ATNState newState() -
label
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listLabel
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tokenRef
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set
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charSetLiteral
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range
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stringLiteral
For a non-lexer, just build a simple token reference atom. For a lexer, a string is a sequence of char to match. That is, "fog" is treated as 'f' 'o' 'g' not as a single transition in the DFA. Machine== o-'f'->o-'o'->o-'g'->o and has n+1 states for n characters. -
ruleRef
For reference to rule r, build o-e->(r) o where (r) is the start of rule r and the trailing o is not linked to from rule ref state directly (it's done thru the transition(0) RuleClosureTransition. If the rule r is just a list of tokens, it's block will be just a set on an edge o->o->o-set->o->o->o, could inline it rather than doing the rule reference, but i'm not doing this yet as I'm not sure it would help much in the ATN->DFA construction. TODO add to codegen: collapse alt blks that are sets into single matchSet- Parameters:
node
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epsilon
From an empty alternative build Grip o-e->o -
sempred
Build what amounts to an epsilon transition with a semantic predicate action. The pred is a pointer into the AST of the SEMPRED token. -
action
Build what amounts to an epsilon transition with an action. The action goes into ATN though it is ignored during analysis. -
action
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alt
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block
ATNFactory.Handle block(BlockAST blockAST, GrammarAST ebnfRoot, List<ATNFactory.Handle> alternativeGrips) From A|B|..|Z alternative block build o->o-A->o->o (last ATNState is blockEndATNState pointed to by all alts) | ^ o->o-B->o--| | | ... | | | o->o-Z->o--| So every alternative gets begin ATNState connected by epsilon and every alt right side points at a block end ATNState. There is a new ATNState in the ATNState in the Grip for each alt plus one for the end ATNState. Special case: only one alternative: don't make a block with alt begin/end. Special case: if just a list of tokens/chars/sets, then collapse to a single edge'd o-set->o graph. Set alt number (1..n) in the left-Transition ATNState. -
optional
From (A)? build either: o--A->o | ^ o---->| or, if A is a block, just add an empty alt to the end of the block -
plus
From (A)+ build |---| (Transition 2 from A.right points at alt 1) v | (follow of loop is Transition 1) o->o-A-o->o Meaning that the last ATNState in A points back to A's left Transition ATNState and we add a new begin/end ATNState. A can be single alternative or multiple. During analysis we'll call the follow link (transition 1) alt n+1 for an n-alt A block. -
star
From (A)* build |---| v | o->o-A-o--o (Transition 2 from block end points at alt 1; follow is Transition 1) | ^ o---------| (optional branch is 2nd alt of optional block containing A+) Meaning that the last (end) ATNState in A points back to A's left side ATNState and we add 3 new ATNStates (the optional branch is built just like an optional subrule). See the Aplus() method for more on the loop back Transition. The new node on right edge is set to RIGHT_EDGE_OF_CLOSURE so we can detect nested (A*)* loops and insert an extra node. Previously, two blocks shared same EOB node. There are 2 or 3 decision points in a A*. If A is not a block (i.e., it only has one alt), then there are two decisions: the optional bypass and then loopback. If A is a block of alts, then there are three decisions: bypass, loopback, and A's decision point. Note that the optional bypass must be outside the loop as (A|B)* is not the same thing as (A|B|)+. This is an accurate ATN representation of the meaning of (A)*, but for generating code, I don't need a DFA for the optional branch by virtue of how I generate code. The exit-loopback-branch decision is sufficient to let me make an appropriate enter, exit, loop determination. See codegen.g -
wildcard
Build an atom with all possible values in its label -
lexerAltCommands
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lexerCallCommand
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lexerCommand
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