From c55c0ada15ebcef74cf6764de8e6cd387d80e4c3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kasper=20Ga=C5=82kowski?= <kpg@posteo.net>
Date: Mon, 28 Mar 2022 16:59:46 +0200
Subject: [PATCH] add CONCATENATE

---
 src/sequence.lisp | 13 +++++++++++++
 tests/seq.lisp    | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/sequence.lisp b/src/sequence.lisp
index 9cf0816f..9fc21d04 100644
--- a/src/sequence.lisp
+++ b/src/sequence.lisp
@@ -458,6 +458,19 @@
 	  (funcall result-collector (apply function args))
 	  (apply function args)))))
 
+(defun check-sequence-type-specifier (specifier)
+  (unless (member specifier '(vector string list))
+    (error "Not a valid sequence type specifier")))
+
+(defun concatenate (result-type &rest sequences)
+  (check-sequence-type-specifier result-type)
+  (let ((iterators (mapcar #'make-iterator sequences))
+        (result-collector (make-collector result-type)))
+    (dolist (it iterators)
+      (do ((arg (funcall it) (funcall it)))
+          ((eq *iterator-done* arg))
+        (funcall result-collector arg)))
+    (funcall result-collector)))
 
 ;;; remove duplicates
 (defun %remove-duplicates (seq from-end test test-not key start end)
diff --git a/tests/seq.lisp b/tests/seq.lisp
index e121213f..761c565f 100644
--- a/tests/seq.lisp
+++ b/tests/seq.lisp
@@ -277,6 +277,24 @@
    (list acc result))
  '((3 2 1) t))
  
+;;; CONCATENATE
+(test-equal
+ (concatenate 'string "all" " " "together" " " "now")
+ "all together now")
+
+(test-equal
+ (concatenate 'list "ABC" '(d e f) #(1 2 3) "1011")
+ '(#\A #\B #\C D E F 1 2 3 #\1 #\0 #\1 #\1))
+
+(test-equal
+ (concatenate 'list)
+ nil)
+
+(test-equal
+ (handler-case
+     (concatenate '(vector * 2) "a" "bc")
+   (error () :signalled))
+ :signalled)
 
 
 ;;; REMOVE-DUPLICATES