11 Typesystem
t, t1, t2, ... are type expressions. v1, v2, ... are type variables
('a, 'b, 'foo, ...).
Basic types: int
, float
, string
, bool
, void
, written as is.
Function type is written as follows:
*(t1, t2, ..., tn) -> t
where n >= 0. One might note that this is somewhat different from ML where
all functions take just one parameter (which can be tuple or another
function, but this is not the point). This is closer to C's function
notation.
Tuples:
*[t1, t2, ..., tn]
where n >= 2.
Structures are defined with:
struct <v1, v2, ..., vn> NAME {
t1 f1;
t2 f2;
...
tm fm;
}
Structures that can be invalid (i.e. null):
opt_struct <v1, v2, ..., vn> NAME {
t1 f1;
t2 f2;
...
tm fm;
}
Unions (datatypes) are defined with:
union <v1, v2, ..., vn> NAME {
t1 f1;
t2 f2;
...
tm fm;
}
where n >= 0, m >= 1. If n == 0, <> can be omitted. fi are field names.
Structures and unions can be later on referred with:
<t1, t2, ..., tn> NAME
where n >= 0. If n == 0, <> can be omitted.
*
in front of tuple and function types is (crude) way to convince
ocamlyacc (Bison has the same problem, though), that there are none
reduce/reduce conflicts in grammar. I guess there aren't even without
`*', but tell it to yacc... (this problem is referred to in Bison manual,
there are some workarounds, however I was unable to make use of it).