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[Caml-list] question: "('a, 'b) Hashtbl.t" and type constraint
- Jean-Baptiste Robertson
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| Date: | -- (:) |
| From: | Jean-Baptiste Robertson <jbrobertson@f...> |
| Subject: | [Caml-list] question: "('a, 'b) Hashtbl.t" and type constraint |
Hello,
OCaml 2.99 complains about the type of the following expression. After
browsing the manual, the FAQ and the like, and after trying every type
forcing I could think of, I am still unable to persuade it to accept the
following piece of code:
1 open Str;;
2
3 let string_hash = Hashtbl.create 7 and
4 regexp_hash = Hashtbl.create 7 and
5 kind = "a" and
6 avalue = "b" in
7 begin
8 if kind = "whatever" then
9 Hashtbl.add string_hash "something" avalue
10 else
11 Hashtbl.add regexp_hash "something" (regexp avalue)
12 end;
13 [ string_hash ; regexp_hash ] ;;
(see below for a cut-and-paste friendly version).
I expected the compiler to bind `string_hash' and `regexp_hash' to
values of the `(string,string) Hashtbl' and `(string,Str.regexp)
Hashtbl'
types, resp., thanks to the 9th and 11th line. All I got is
File "ex.ml", line 13, characters 16-27:
This expression has type (string, Str.regexp) Hashtbl.t
but is here used with type (string, string) Hashtbl.t
Replacing the 4th line by
let regexp_hash = (Hashtbl.create 7 : (string, Str.regexp) Hashtbl.t );;
doesn't help.
I may be missing the obvious. No idea.
Any help is appreciated.
TIA
jb
_____________________________
open Str;;
let string_hash = Hashtbl.create 7 and
regexp_hash = Hashtbl.create 7 and
kind = "a" and
avalue = "b" in
begin
if kind = "whatever" then
Hashtbl.add string_hash "something" avalue
else
Hashtbl.add regexp_hash "something" (regexp avalue)
end;
[ string_hash ; regexp_hash ] ;;
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