interpose: use seq_iter and seq_build.

* lib.c (interpose): non-list cases consolidated into
one, which uses generic iteration and building.

* tests/012/seq.tl: New tests

2 files changed, 32 insertions, 7 deletions

diff --git a/lib.c b/lib.c
index 1d06d645..7a0d2522 100644
--- a/lib.c
+++ b/lib.c
@@ -11151,6 +11151,8 @@ static val lazy_interpose(val sep, val list)
 
 val interpose(val sep, val seq)
 {
+  val self = lit("interpose");
+
   switch (type(seq)) {
   case NIL:
     return nil;
@@ -11171,14 +11173,26 @@ val interpose(val sep, val seq)
     }
   case LCONS:
     return lazy_interpose(sep, seq);
-  case LIT:
-  case STR:
-  case LSTR:
-    return cat_str(interpose(sep, tolist(seq)), nil);
-  case VEC:
-    return vec_list(interpose(sep, tolist(seq)));
   default:
-    type_mismatch(lit("interpose: ~s is not a sequence"), seq, nao);
+    {
+      seq_build_t bu;
+      seq_iter_t it;
+      val elem;
+
+      seq_build_init(self, &bu, seq);
+      seq_iter_init(self, &it, seq);
+
+      if (seq_get(&it, &elem)) {
+        seq_add(&bu, elem);
+
+        while (seq_get(&it, &elem)) {
+          seq_add(&bu, sep);
+          seq_add(&bu, elem);
+        }
+      }
+
+      return seq_finish(&bu);
+    }
   }
 }
 
diff --git a/tests/012/seq.tl b/tests/012/seq.tl
index 262c7739..c3000b5e 100644
--- a/tests/012/seq.tl
+++ b/tests/012/seq.tl
@@ -883,3 +883,14 @@
 
 (mtest
   (ref 1..6 0.0) (1.0 2.0 3.0 4.0 5.0))
+
+(mtest
+  (interpose 1 '()) ()
+  (interpose 1 '(a)) (a)
+  (interpose 1 '(a b)) (a 1 b)
+  (interpose 1 '(a b c)) (a 1 b 1 c))
+
+(mtest
+  (interpose 1 "") ""
+  (interpose 1 "a") "a"
+  (interpose 1 "ab") (#\a 1 #\b))