Transition from exception-based errors to printf-based

1 files changed, 3 insertions, 0 deletions

diff --git a/common.sml b/common.sml
index 31a9940..f2020e2 100644
--- a/common.sml
+++ b/common.sml
@@ -36,6 +36,7 @@ structure Fold = struct
   fun step0 h (a, f) = fold (h a, f)
   fun step1 h (a, f) b = fold (h (b, a), f)
   fun step2 h (a, f) b c = fold (h (b, c, a), f)
+  fun step3 h (a, f) b c d = fold (h (b, c, d, a), f)
 end
 
 structure FRU = struct
@@ -128,6 +129,8 @@ in
     (ifF ign (fn () => f output); (ign, output))) z
   fun A1 z = Fold.step2 (fn (f, v, (ign, output)) =>
     (ifF ign (fn () => f (output, v)); (ign, output))) z
+  fun A2 z = Fold.step3 (fn (f, v1, v2, (ign, output)) =>
+    (ifF ign (fn () => f (output, v1, v2)); (ign, output))) z
 end
 
 fun Ign z = Fold.step0 (fn (_, output) => (true, output)) z