手动调整 env/stack/semantic 值以实现错误恢复

Question

我正在尝试在 this version of the project 中实现错误恢复（make 后跟 ./parse e1.input 进行测试）。

给定 e1.input 中的 (1，我希望解析器像解析 ) 一样运行并构建 AST Paren (Int 1)。因此，我尝试了

let (startp, endp) = positions in
let _ = feed (T T_RPAREN) startp () endp env in

然而，它返回了一个错误Invalid_argument("feed: outgoing transition does not exist")

hahahaha depth of env 2
hahahaha current_state_number 2
hahahaha startp 1:1
hahahaha endp   1:2

element number of state 2
element startp 1:1
element endp   1:2
element incoming_symbol an integer
element v toComplete
element item: an expression -> an integer.

element number of state 1
element startp 1:0
element endp   1:1
element incoming_symbol (
element v toComplete
element item: an expression -> ( .an expression )

Line 1, characters 2-2: Error (parsing)
  Error while analyzing an expression.
Fatal error: exception Invalid_argument("feed: outgoing transition does not exist")

有谁知道为什么会出现这个错误？

Answer 1

在喂)之前，我们应该先reduce，下面的代码有效：

let env_new = force_reduction (find_production 1) env in
let env_new_new = feed (T T_RPAREN) startp () endp env_new in
(lex, input_needed env_new_new)

例如(1+2，我们应该在喂)之前减少两次，下面的代码有效：

let env_new = force_reduction (find_production 1) env in
let env_new_new = force_reduction (find_production 3) env_new in
let env_new_new_new = feed (T T_RPAREN) startp () endp env_new_new in
(lex, input_needed env_new_new_new)

手动调整 env/stack/semantic 值以实现错误恢复

Manually tweak env/stack/semantic value to achieve an error recovery

parsing

ocaml

error-recovery

menhir