buffers: allow inequality comparison with less.

* lib.c (less_tab_init): Assign category 6 to BUF type, so
buffers are sorted after other types.
(less): Add BUF case.

* txr.1: Documented.

2 files changed, 21 insertions, 3 deletions

diff --git a/lib.c b/lib.c
index f4f47b76..862bb1ce 100644
--- a/lib.c
+++ b/lib.c
@@ -4563,6 +4563,7 @@ static void less_tab_init(void)
   type_prec[BGNUM] = 1;
   type_prec[FLNUM] = 1;
   type_prec[RNG] = 2;
+  type_prec[BUF] = 6;
 
   for (l = 0; l <= MAXTYPE; l++)
     for (r = 0; r <= MAXTYPE; r++) {
@@ -4689,6 +4690,19 @@ tail:
 
       return nil;
     }
+  case BUF:
+    {
+      cnum ll = c_num(left->b.len);
+      cnum rl = c_num(right->b.len);
+      cnum len = min(ll, rl);
+      int cmp = memcmp(left->b.data, right->b.data, len);
+
+      if (cmp < 0 || (cmp == 0 && ll < rl))
+        return t;
+
+      return nil;
+    }
+    break;
   default:
     internal_error("unhandled case in less function");
   }
diff --git a/txr.1 b/txr.1
index 26568b71..75695f3e 100644
--- a/txr.1
+++ b/txr.1
@@ -17971,7 +17971,7 @@ and
 The
 .code less
 function is capable of comparing numbers, characters, symbols, strings,
-as well as lists and vectors of these.
+as well as lists and vectors of these. It can also compare buffers.
 
 If both arguments are the same object so that
 .mono
@@ -18047,7 +18047,6 @@ Note that the empty
 list nil compared to a cons is handled by type-based precedence, described
 below.
 
-
 Two vectors are compared by
 .code less
 lexicographically, similarly
@@ -18063,6 +18062,10 @@ is the outcome of comparing those differing elements themselves
 with
 .codn less .
 
+Two buffers are also compared by
+.code less
+lexicographically, as if they were vectors of integer byte values.
+
 Two ranges are compared by
 .code less
 using lexicographic logic similar to conses and vectors.
@@ -18088,7 +18091,8 @@ then
 .code less
 resolves the situation based on the following precedence: numbers and
 characters are less than ranges, which are less than strings, which are less
-than symbols, which are less than conses, which are less than vectors.
+than symbols, which are less than conses, which are less than vectors,
+which are less than buffers.
 
 Note that since
 .code nil