Is it possible to capture unescaped text with ppxlib?

Learning
1

By “unescaped” I mean something like:

a /\ b =>
c

Note that the newline is literally newline not “\n” and the backslash is not escaped. Is it possible to write this in a ppx expansion and capture the string literal from it?

2

The payload type declared in parsetree.mli does not seem to allow it. I guess one needs to work with the lexer if one wants the raw text quotation instead of working with the parsetree.

3
  1. I think It’s not easy to define infix operator (/\)…
  2. You could try to parse this expression as it is and after that try to reconstruct it back using locations of every identifier in the expression.
4

If you just want the string itself, can’t you just use the string literal syntax:

let x = {|a /\ b =>
  c
 |}

If you instead are trying to get a raw string to use within a ppx rewriter, you can reuse the string literal syntax no?:

let x = {%my_ppx|a /\ b =>
  c
 |}
1 Like
5

I need to write a ppx rewriter. I didn’t come across any reference on this. Thanks! I will give it a try:

6

The quoted string syntax for extension node ({%ext|...|} and {%%ext|...|}) is described in the extension node section of the manual.

2 Likes
7

I was able to get this to work

let t = [%q{|a /\ b|}];;

in utop, but utop didn’t accept the shorthand version.

Cool! Thanks!

1 Like
8

The shorthand version was only added in 4.11.0, this is probably the reason it is not working in utop for you.

1 Like
9

That must be it. I am still on 4.10.2.