[MLton-user] Extended Basis Library: proposed sequence concept

[Geoffrey Alan Washburn]

	I was starting on a »generic« zip/unzip library for
sequences,but realized that there was not any actual common
ancestry for the signatures in the sequence directory.  I put
this together by distilling the commonality between lists,
arrays, and vectors.  There actually could be more
commonality between them; I noticed at least the following
discrepancies:

    - List does not have »extract«.
    - List's »mapi«/»appi«/etc. are different in form than
      those in Array and Vector.
    - Array does not have »concat«, though I would agree that
      whether it should is debatable.
    - List does not have »fromList« and »toList«.  While
      trivial, these would add further uniformity.
    - Array and Vector could possibly support a number of
      list-like operations that they currently don't:
      »hd«, »tl«, »rev«, etc.

Index: sequence.sig
===================================================================
--- sequence.sig	(revision 0)
+++ sequence.sig	(revision 0)
@@ -0,0 +1,43 @@
+(* Copyright (C) 2007 ????
+ *
+ * This code is released under the MLton license, a BSD-style license.
+ * See the LICENSE file or http://mlton.org/License for details.
+ *)
+
+(** == Sequences ==
+ *
+ * Sequence types are polymorphic containers that has a linear
+ * ordering on its elements.  Sequences do not need to be
+ * finite, but some additional operations are available for
+ * sequences those that are known to be finite or infinite
+ * respectively.
+ *)
+
+(** === All sequences == *)
+
+signature SEQUENCE_CORE = sig
+  type 'a seq
+  val sub : 'a seq * Int.t -> 'a
+  val map : ('a -> 'b) -> 'a seq -> 'b seq
+  val app : 'a Effect.t -> 'a seq Effect.t
+  val foldr : ('a * 'b -> 'b) -> 'b -> 'a seq -> 'b
+end
+
+(** === Finite sequences == *)
+
+signature SEQUENCE_FINITE = sig
+  type 'a seq_fin
+  val empty : 'a seq_fin
+  val length : 'a seq_fin -> Int.t
+  val foldl : ('a * 'b -> 'b) -> 'b -> 'a seq_fin -> 'b
+  val tabulate : (Int.t * (Int.t -> 'a)) -> 'a seq_fin
+end
+
+(** === Infinite sequences == *)
+
+signature SEQUENCE_INFINITE = sig
+  type 'a seq_inf
+
+  val iteratei : (Int.t * 'a -> 'a) -> 'a seq_inf
+  val iterate : ('a -> 'a) -> 'a seq_inf
+end
+

Property changes on: sequence.sig
___________________________________________________________________
Name: svn:eol-style
    + native