1 files changed, 61 insertions, 0 deletions
diff --git a/interpret/data.ml b/interpret/data.ml
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+++ b/interpret/data.ml
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+(* Data structures for representing the state of a system *)
+
+open Util
+open Ast
+
+exception Combinatorial_cycle of string
+exception No_variable of string
+exception Type_error of string
+let type_error e = raise (Type_error e)
+exception Not_implemented of string
+let not_implemented e = raise (Not_implemented e)
+
+type scope = string
+
+type svalue =
+  | VInt of int
+  | VBool of bool
+  | VReal of float
+  | VState of id
+  | VPrevious of value
+  | VBusy   (* intermediate value : calculating ! for detection of cycles *)
+and value = svalue list
+
+type state = svalue VarMap.t
+
+(* functions for recursively getting variables *)
+
+type calc_fun = 
+  | F of (state -> calc_map -> state)
+and calc_map = calc_fun VarMap.t
+
+let get_var (st: state) (c: calc_map) (id: id) : (state * svalue) =
+  let st =
+    if VarMap.mem id st then st
+    else try match VarMap.find id c with
+    | F f ->
+      Format.printf "%s[ " id;
+      let r = f (VarMap.add id VBusy st) c in
+      Format.printf "]%s " id;
+      r
+    with Not_found -> raise (No_variable id)
+  in
+    match VarMap.find id st with
+    | VBusy -> raise (Combinatorial_cycle id)
+    | v -> st, v
+
+(* pretty-printing *)
+
+let rec str_of_value = function
+  | VInt i -> string_of_int i
+  | VReal r -> string_of_float r
+  | VBool b -> if b then "true" else "false"
+  | VState s -> "state " ^ s
+  | VPrevious p ->
+    "[" ^
+      List.fold_left (fun s v -> (if s = "" then "" else s ^ ", ") ^ str_of_value v) "" p
+      ^ "]"
+  | VBusy -> "#"
+let print_state st =
+  VarMap.iter (fun id v -> Format.printf "%s = %s@." id (str_of_value v)) st
+