add rule module

diff --git a/driver/OMakefile b/driver/OMakefile
index 1551d6f..68b18c1 100644 (file)
--- a/driver/OMakefile
+++ b/driver/OMakefile
@@ -46,6 +46,7 @@ BYTE_ENABLED = true
 #
 
 FILES[] =
+       rule
        main
 
 PROGRAM = habc

diff --git a/driver/rule.ml b/driver/rule.ml
new file mode 100644 (file)
index 0000000..f0eba12
--- /dev/null
+++ b/driver/rule.ml
@@ -0,0 +1,44 @@
+open Base
+exception NoRuleFailure
+
+type t = {
+  src : string;
+  dest: string;
+  cmd : string -> string -> string list
+}
+
+let (=>) a b =
+  (a,b)
+let (<>) (a,b) f = {
+  src  = a;
+  dest = b;
+  cmd  = f
+}
+
+let is_reach dest {dest=dest'} =
+  dest = dest'
+
+let reachable dest rules =
+  List.filter (is_reach dest) rules
+
+let minimum_by f xs =
+  let min a b =
+    if f a b then a else b in
+    match xs with
+      | [] ->
+         invalid_arg "empty list"
+    | y::ys ->
+       List.fold_left min y ys
+
+let rec shortest rules src dest =
+  if src = dest then
+    0,[]
+  else
+    let reachable =
+      List.map
+       (fun ({src=src'} as r) ->
+          let (cost,routes) =
+            shortest rules src src' in
+            cost+1,r::routes) @@
+       reachable dest rules in
+      minimum_by (fun (a,_) (b,_) -> a < b) reachable