main
%%
main:
separated_list(STRING, COMMA) EOF { $1 }
```
And the lexer something like that :
```auto
{
open Parser
open LexerHelper
}
let atom_code = ('\\' digit (digit ?) (digit ?)) | ("\\0x" hexdigit (hexdigit ?))
let string_printable = [' ' - '!' '#' - '~']
let string_atom = string_printable | atom_code | "\\t" | "\\r" | "\\b" | "\\n" | "\\\"" | "\\\\"
let whitespace = [' ' '\n' '\t' '\r']*
rule string accumulator = parse
| "\"" { STRING(
String.of_seq
(List.to_seq
(List.map (char_of_atom lexbuf)
(List.rev accumulator)))) }
| string_atom { string ((Lexing.lexeme lexbuf) :: accumulator) lexbuf }
| eof { error "during lexing" (Position.cpos lexbuf) "Unterminated string." }
and token = parse
| whitespace { token lexbuf }
| "," { COMMA }
| "\"" { string [] lexbuf }
| eof { EOF }
```
And a lexerHelper.ml file with the following code :
```ocaml
let char_of_atom lexbuf atom =
match atom with
| {|\n|} -> '\n'
| {|\t|} -> '\t'
| {|\b|} -> '\b'
| {|\r|} -> '\r'
| {|\\|} -> '\\'
| {|\'|} -> '\''
| {|\"|} -> '"'
| _ when String.length atom = 1 -> atom.[0]
| _ when atom.[0] = {|\|}.[0] -> (
try Char.chr (int_of_string (String.sub atom 1 (String.length atom - 1)))
with Invalid_argument _ ->
error "during lexing" (Position.cpos lexbuf) "" )
| _ -> failwith "Should never happen"
```
Note that I did not test any of this, I just pieced it together from old code of mine. For dune rules, and general organisation, you can look at this small DSL of mine : [chat\_botte/src/rolelang at master · EmileTrotignon/chat\_botte · GitHub](https://github.com/EmileTrotignon/chat_botte/tree/master/src/rolelang).
---
### Author:  [@SeedyROM](https://discuss.ocaml.org/u/SeedyROM)
#### Post date: [November 18, 2021, 12:39pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/3 "2021-11-18T12:39:10Z")
@EmileTrotignon
Gonna read through this in more detail later, as I’m on PST time right now where I am and it’s getting hyper late.
**Thanks for the example!**
---
### Author:  [@Gopiandcode](https://discuss.ocaml.org/u/Gopiandcode)
#### Post date: [November 18, 2021, 12:46pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/4 "2021-11-18T12:46:17Z")
I have an example of using Menhir+OCamllex for a custom dsl here: [parser · master · Kiran Gopinathan / GSDL - Gop-Scene Definition Language · GitLab](https://gitlab.com/gopiandcode/gsdl/-/tree/master/parser)
Relevant files are probably `lexer.mll`, `parser.mly` and `dune`.
Although more recently I’ve started using sedlex instead of ocamllex for my lexers because sedlex allows me to use normal OCaml syntax (and hence + merlin + gopcaml-mode for editing).
For other examples of Menhir parsers, the OCaml parser is also written in menhir and might be worth checking out as well.
---
### Author:  [@EmileTrotignon](https://discuss.ocaml.org/u/EmileTrotignon)
#### Post date: [November 18, 2021, 12:51pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/5 "2021-11-18T12:51:13Z")
Sedlex is a little complicated to plug into menhir because it does not use the same lexbuf type as ocamllex. Its a lot nicer to use though.
---
### Author:  [@Gopiandcode](https://discuss.ocaml.org/u/Gopiandcode)
#### Post date: [November 18, 2021, 12:56pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/6 "2021-11-18T12:56:20Z")
Yeah, good point - it does require a bit more boilerplate, although not too much nowadays.
This was all the extra code I needed to glue between the two interfaces for a recent project:
```auto
exception Error
let revised_parse lexbuf =
let tok () =
let tok = Lexer.token lexbuf in
let (st,ed) = Sedlexing.lexing_positions lexbuf in
(tok,st,ed) in
MenhirLib.Convert.Simplified.traditional2revised
Raw_parser.program
tok
let parse lexbuf =
try
revised_parse lexbuf
with Raw_parser.Error -> raise Error
let parse_string str =
parse (Sedlexing.Utf8.from_string str)
```
edit: fixed locations
---
### Author:  [@EmileTrotignon](https://discuss.ocaml.org/u/EmileTrotignon)
#### Post date: [November 18, 2021, 1:55pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/7 "2021-11-18T13:55:04Z")
This forces you to use the table backend though ? This backend is quite slower (does not make a difference for most uses). I believe there should be a way to provide an “abstract” buffer to menhir, that is a function of type `unit -> token` and two of type `unit -> position`. But its not available yet.
---
### Author:  [@pmonson711](https://discuss.ocaml.org/u/pmonson711)
#### Post date: [November 18, 2021, 5:05pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/8 "2021-11-18T17:05:59Z")
I’ve found this to be a well written set of articles and reasonably complete example language.
> **[Writing a Lexer and Parser using OCamllex and Menhir](https://mukulrathi.com/create-your-own-programming-language/parsing-ocamllex-menhir/)**
>
> The first stage of a compiler is to represent our Bolt program in a structured format. In this post, I explain how lexing and parsing work, and how we use OCamllex and Menhir to generate the lexer and parser for Bolt. I'll also cover how to fix cases...
---
### Author:  [@vrotaru](https://discuss.ocaml.org/u/vrotaru)
#### Post date: [November 19, 2021, 9:06am UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/9 "2021-11-19T09:06:11Z")
The is the PL Zoo where you can find many such examples.
> **[GitHub - andrejbauer/plzoo: Programming Languages Zoo](https://github.com/andrejbauer/plzoo)**
>
> Programming Languages Zoo. Contribute to andrejbauer/plzoo development by creating an account on GitHub.
---
### Author:  [@roddy](https://discuss.ocaml.org/u/roddy)
#### Post date: [November 20, 2021, 12:41pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/10 "2021-11-20T12:41:20Z")
Real World OCaml has an [example](https://dev.realworldocaml.org/parsing-with-ocamllex-and-menhir.html) of JSON parsing.
---
### Author:  [@smolkaj](https://discuss.ocaml.org/u/smolkaj)
#### Post date: [November 20, 2021, 6:28pm UTC](https://discuss.ocaml.org/t/ocamllex-and-menhir-examples-that-arent-calculators/8843/11 "2021-11-20T18:28:24Z")
[nice-parser](https://github.com/smolkaj/nice-parser) has an [example](https://github.com/smolkaj/nice-parser/tree/master/example) of how to parse S-expressions. It’s a tiny library that encapsulates all the typical boilerplate code, so you can just focus on lexing and parsing.