I can't quite understand the syntax used here:
let rec lex = parser
(* Skip any whitespace. *)
| [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream
Firstly, I don't understand what it means to use a guard (vertical line) followed by parser.
And secondly, I can't seem to find the relevant syntax for the condition surrounded by [< and >]
Got the code from here. Thanks in advance!
As @glennsl says, this page uses the campl4 preprocessor, which is considered obsolete by many in the OCaml community.
Here is a forum message from August 2019 that describes how to move from camlp4 to the more recent ppx:
Unfortunately that doesn't really help you learn what that LLVM page is trying to teach you, which has little to do with OCaml it seems.
This is one reason I find the use of syntax extensions to be problematic. They don't have the staying power of the base language.
(On the other hand, OCaml really is a fantastic language for writing compilers and other language tools.)