I'm trying to write something like this:
type 'a 'b xxx = {aaa: 'a: bbb: 'b: ccc: int};;
It does not compile. Is it just syntax error, or they don't allow multiple paramters on type ? Then why ?
+8
A:
In ML, multiple type parameters are written between parentheses and separated by commas, like this:
type ('a,'b) xxx = {aaa: 'a; bbb: 'b; ccc: int; }
nlucaroni
2010-05-25 04:01:20
I always interpreted it as the deconstruction of components of a single triple/tuple/... How are the two definitions different? Or, what implications does the difference mean? How does ocaml use them differently then?
nlucaroni
2010-05-26 15:22:28
nlucaroni: I believe this is just syntax. Multiparameter types are just that - type parameterized by several parameters, compiler only needs to know how many parameters are present. Tuple types are different - they define a 'structure' of the value. Hope I didn't mess up badly with terminology :)
ygrek
2010-05-27 06:47:22
+3
A:
Actually you can write like this, in revised syntax :
Objective Caml version 3.11.2
# #load "dynlink.cma";;
# #load "camlp4r.cma";;
Camlp4 Parsing version 3.11.2
# type xxx 'a 'b = { aaa : 'a; bbb: 'b; ccc: int};
type xxx 'a 'b = { aaa : 'a; bbb : 'b; ccc : int }
ygrek
2010-05-25 12:17:35