OCaml parser combinator that compiles to direct recursive descent
specialised fast paths for common patterns (many/some with token, satisfy, any)
author
vm.fail
date
(Jan 16, 2026, 10:03 PM UTC)
commit
81c9c703
81c9c70347ca90bc76cd6fc5b906897b5c2eec4c
parent
25d8d7e2
25d8d7e264c768416b4d35b8112e451f133443a6
vm.fail
date
(Jan 16, 2026, 10:03 PM UTC)
commit
81c9c703
81c9c70347ca90bc76cd6fc5b906897b5c2eec4c
parent
25d8d7e2
25d8d7e264c768416b4d35b8112e451f133443a6
+84
-19
+84
-19
src/codegen.ml
+84
-19
src/codegen.ml
···
179
179
| Error _ -> Ok ((), saved)]
180
180
181
181
| Many { p; loc } ->
182
-
let p_code = compile ~loc env p in
183
-
[%expr
184
-
let rec loop acc input =
185
-
match [%e p_code] with
186
-
| Ok (x, inp) -> loop (x :: acc) inp
187
-
| Error _ -> Ok (List.rev acc, input)
188
-
in
189
-
loop [] input]
182
+
(match p with
183
+
| Token { tok; _ } ->
184
+
[%expr
185
+
let rec loop acc input =
186
+
match I.peek input with
187
+
| Some t when t = [%e tok] -> loop (t :: acc) (I.advance input)
188
+
| _ -> Ok (List.rev acc, input)
189
+
in
190
+
loop [] input]
191
+
| Satisfy { pred; _ } ->
192
+
[%expr
193
+
let rec loop acc input =
194
+
match I.peek input with
195
+
| Some t when [%e pred] t -> loop (t :: acc) (I.advance input)
196
+
| _ -> Ok (List.rev acc, input)
197
+
in
198
+
loop [] input]
199
+
| Any _ ->
200
+
[%expr
201
+
let rec loop acc input =
202
+
match I.peek input with
203
+
| Some t -> loop (t :: acc) (I.advance input)
204
+
| None -> Ok (List.rev acc, input)
205
+
in
206
+
loop [] input]
207
+
| _ ->
208
+
let p_code = compile ~loc env p in
209
+
[%expr
210
+
let rec loop acc input =
211
+
match [%e p_code] with
212
+
| Ok (x, inp) -> loop (x :: acc) inp
213
+
| Error _ -> Ok (List.rev acc, input)
214
+
in
215
+
loop [] input])
190
216
191
217
| Some_ { p; loc } ->
192
-
let p_code = compile ~loc env p in
193
-
[%expr
194
-
match [%e p_code] with
195
-
| Ok (x, inp) ->
196
-
let rec loop acc input =
197
-
match [%e p_code] with
198
-
| Ok (y, inp2) -> loop (y :: acc) inp2
199
-
| Error _ -> Ok (List.rev acc, input)
200
-
in
201
-
loop [x] inp
202
-
| Error e -> Error e]
218
+
(match p with
219
+
| Token { tok; _ } ->
220
+
[%expr
221
+
match I.peek input with
222
+
| Some t when t = [%e tok] ->
223
+
let rec loop acc input =
224
+
match I.peek input with
225
+
| Some t when t = [%e tok] -> loop (t :: acc) (I.advance input)
226
+
| _ -> Ok (List.rev acc, input)
227
+
in
228
+
loop [t] (I.advance input)
229
+
| _ -> [%e error_expr ~loc [%expr [I.show_token [%e tok]]]]]
230
+
| Satisfy { pred; label; _ } ->
231
+
let expected = match label with
232
+
| Some l -> elist ~loc [estring ~loc l]
233
+
| None -> [%expr ["<satisfy>"]]
234
+
in
235
+
[%expr
236
+
match I.peek input with
237
+
| Some t when [%e pred] t ->
238
+
let rec loop acc input =
239
+
match I.peek input with
240
+
| Some t when [%e pred] t -> loop (t :: acc) (I.advance input)
241
+
| _ -> Ok (List.rev acc, input)
242
+
in
243
+
loop [t] (I.advance input)
244
+
| _ -> [%e error_expr ~loc expected]]
245
+
| Any _ ->
246
+
[%expr
247
+
match I.peek input with
248
+
| Some t ->
249
+
let rec loop acc input =
250
+
match I.peek input with
251
+
| Some t -> loop (t :: acc) (I.advance input)
252
+
| None -> Ok (List.rev acc, input)
253
+
in
254
+
loop [t] (I.advance input)
255
+
| None -> [%e error_expr ~loc (elist ~loc [estring ~loc "<any>"])]]
256
+
| _ ->
257
+
let p_code = compile ~loc env p in
258
+
[%expr
259
+
match [%e p_code] with
260
+
| Ok (x, inp) ->
261
+
let rec loop acc input =
262
+
match [%e p_code] with
263
+
| Ok (y, inp2) -> loop (y :: acc) inp2
264
+
| Error _ -> Ok (List.rev acc, input)
265
+
in
266
+
loop [x] inp
267
+
| Error e -> Error e])
203
268
204
269
| Optional { p; loc } ->
205
270
let p_code = compile ~loc env p in