New functions: find-max-key and find-min-key.

* eval.c (eval_init): Register find-max-key and find-min-key
intrinsics.

* lib.c (find_max_key, find_min_key): New functions.

* lib.h (find_max_key, find_min_key): Declared.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.

1 files changed, 30 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 2a3b7680..ba8dca50 100644
--- a/lib.c
+++ b/lib.c
@@ -10940,11 +10940,41 @@ val find_max(val seq, val testfun, val keyfun)
   }
 }
 
+val find_max_key(val seq, val testfun_in, val keyfun_in)
+{
+  val self = lit("find-max-key");
+  val testfun = default_arg(testfun_in, greater_f);
+  val keyfun = default_arg(keyfun_in, identity_f);
+  seq_iter_t iter;
+  val elem;
+
+  seq_iter_init(self, &iter, seq);
+
+  if (seq_get(&iter, &elem)) {
+    val maxkey = funcall1(keyfun, elem);
+
+    while (seq_get(&iter, &elem)) {
+      val key = funcall1(keyfun, elem);
+      if (funcall2(testfun, key, maxkey))
+        maxkey = key;
+    }
+
+    return maxkey;
+  }
+
+  return nil;
+}
+
 val find_min(val seq, val testfun, val keyfun)
 {
   return find_max(seq, default_arg(testfun, less_f), keyfun);
 }
 
+val find_min_key(val seq, val testfun, val keyfun)
+{
+  return find_max_key(seq, default_arg(testfun, less_f), keyfun);
+}
+
 val find_true(val pred, val seq, val key)
 {
   val self = lit("find-true");