New functions [transition_tokens] and [reduction_tokens] in Lr0.

src/lr0.ml

@@ -371,6 +371,16 @@ let transition
   in
   (k, Array.map (interpret state) sr)
 
+(* [transition_tokens transitions] returns the set of tokens (terminal symbols)
+   that are labels of outgoing transitions in the table [transitions]. *)
+
+let transition_tokens transitions =
+  SymbolMap.fold (fun symbol _target toks ->
+    match symbol with
+    | Symbol.T tok -> TerminalSet.add tok toks
+    | Symbol.N _   -> toks
+  ) transitions TerminalSet.empty
+
 (* Equality of states. *)
 
 let equal ((k1, toksr1) as state1) ((k2, toksr2) as state2) =
@@ -636,6 +646,14 @@ let reductions_table state =
     add_reductions prod toks reductions
   ) TerminalMap.empty (reductions state)
 
+(* [reduction_tokens reductions] returns the domain of the reductions table
+   [table], in the form of a set of tokens. *)
+
+let reduction_tokens reductions =
+  TerminalMap.fold (fun tok _prods toks ->
+      TerminalSet.add tok toks
+  ) reductions TerminalSet.empty
+
 (* This inverts a mapping of tokens to productions into a mapping of
    productions to sets of tokens. *)
 

src/lr0.mli

@@ -85,6 +85,11 @@ val start: node -> lr1state
 val transitions: lr1state -> lr1state SymbolMap.t
 val transition: Symbol.t -> lr1state -> lr1state
 
+(* [transition_tokens transitions] returns the set of tokens (terminal symbols)
+   that are labels of outgoing transitions in the table [transitions]. *)
+
+val transition_tokens: 'target SymbolMap.t -> TerminalSet.t
+
 (* Information about the reductions at a state. *)
 
 (* See also [reductions_table] further on. *)
@@ -169,6 +174,11 @@ val reductions_table: lr1state -> reductions
 
 val invert : reductions -> TerminalSet.t ProductionMap.t
 
+(* [reduction_tokens reductions] returns the domain of the reductions table
+   [table], in the form of a set of tokens. *)
+
+val reduction_tokens: reductions -> TerminalSet.t
+
 (* [has_eos_conflict transitions reductions] tells whether a state has
    an end-of-stream conflict, that is, a reduction action on [#] and
    at least one other (shift or reduce) action. *)