# HG changeset patch
# User Chris Cannam
# Date 1745093145 -3600
#      Sat Apr 19 21:05:45 2025 +0100
# Node ID f8ef248a0aad85f99693991b1025393baf36df5e
# Parent  46b1d661f7b0f60da0876f271a83569aa527fa8f
Comments

diff --git a/backing-file.sig b/backing-file.sig
--- a/backing-file.sig
+++ b/backing-file.sig
@@ -1,4 +1,7 @@
-                         
+
+(** A file to which vectors can be written and read. All indexing is
+    done in units of the vector's element size.
+ *)
 signature BACKING_FILE_BASE = sig
 
     type file
@@ -40,6 +43,12 @@
                         
 end
 
+(** BACKED_VECTOR stores a vector to some representation (nominally a
+    file) and allows the whole thing or individual values to be read
+    back again. The file type is not constrained in the signature, but
+    the file is specified, because implementations may allow storing
+    more than one vector in the same file.
+ *)
 signature BACKED_VECTOR = sig
 
     type elem