Following discussions and some rants on polyadic arrays
and compact linear types, and of course the "dynamic" issue,
I have decided to do some experiments in Felix.
Rants deleted .. just run the code!
[You WILL need the latest Felix, because I have changed lists
so that a list is now also an array]
// Type descriptors.
// First cut, doesn't handle recursion!
class Desc
{
union typecode =
| Primitive of string // for now, just the name of a primitive type eg "int"
etc
| Tuple of list[typecode] // a tuple of various types
| Array of int * typecode // an array
;
instance Str[typecode] {
fun str : typecode -> string =
| Primitive ?s => s
| Tuple Empty => "()"
| Tuple (Cons (?h, ?t)) =>
"(" +
fold_left (fun (acc:string) (x:typecode) => acc + "," + x.str) (h.str)
t
+ ")"
| Array (?n, ?t) => str t + "^" + Str::str n
;
}
// example:
var ex1 = Array (3, Tuple ( Primitive "int", Primitive "string").list );
println$ ex1;
union selector =
| Choice of int // pick one of the tree nodes
;
typedef path = list[selector];
fun component (t: typecode) (i: path) =>
match t,i with
| _, Empty => t
// | Primitive _, _ => fail "ERROR" // fail doesn't unify properly at the
moment
| Tuple ?ts, Cons (Choice ?i, ?tail) => component ts.i tail
| Array (_,?t), Cons (Choice _, ?tail) => component t tail
endmatch
;
// example:
println$ component ex1 (Choice 1).list;
}
--
john skaller
[email protected]
http://felix-lang.org
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