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open Types
open Headers
(* Function for stepping through a TDFA computation *)
let step (automaton : tdfa) (state : tdfa_state) : tdfa_state =
match state.to_parse with
| [] -> state
| c :: cs ->
try
let next_state_id, f = automaton.delta (state.state_id, c) in
let next_tok = f state.register in
{
state_id = next_state_id;
register = next_tok;
tokens = state.tokens;
to_parse = cs
}
with (No_Transition (_, c)) ->
let token_to_add = state.register in
let next_state_id, f = automaton.delta (0, c) in
let next_tok = f SKIP in
{
state_id = next_state_id;
register = next_tok;
tokens = if token_to_add <> SKIP then token_to_add :: state.tokens else state.tokens;
to_parse = cs
}
(* Driver to perform a TDFA computation *)
let rec driver (automaton : tdfa) (state: tdfa_state) : tok list =
if
state.to_parse = []
then
List.rev (state.register :: state.tokens) (* ensure that final tag is emitted *)
else
driver automaton (step automaton state)
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