forge:repl: allow list input over multiple lines, using handler-bind and restart-case in string-iterator

forge/forge.lisp

@@ -85,7 +85,11 @@
 (defun repl ()
   (do ((input (read-line) (read-line))) 
       ((string= input "q") (stack *forge-env*))
-    (exec-string input)))
+    (handler-bind
+      ((end-of-file
+         (lambda (c)
+           (invoke-restart 'iter:try-with-more-input (read-line)))))
+      (exec-string input))))
 
 (defun exec-list (lst)
   (let ((*input* (iter:list-iterator lst)))

util/iter.lisp

@@ -6,7 +6,8 @@
 (defpackage :scopes/util/iter
   (:use :common-lisp)
   (:export #:stop #:next #:value #:next-value #:process
-           #:list-iterator #:string-iterator #:stream-iterator))
+           #:list-iterator #:string-iterator #:stream-iterator
+           #:try-with-more-input))
 
 (in-package :scopes/util/iter)
 
@@ -56,7 +57,7 @@
 ;;;; string iterator implementation
 
 (defclass string-iterator (iterator)
-  ((data :reader data :initarg :data :initform "")
+  ((data :accessor data :initarg :data :initform "")
    (curpos :accessor curpos :initform 0)
    (value :accessor value :initform nil)))
 
@@ -64,14 +65,18 @@
   (make-instance 'string-iterator :data s))
 
 (defmethod next ((it string-iterator))
-  (let ((pos (curpos it)))
-    (if (< pos (length (data it)))
-      (multiple-value-bind (val newpos) 
-                           (read-from-string (data it) nil nil :start pos)
-        (setf (curpos it) newpos 
-              (value it) val)
-        nil)
-      t)))
+  (restart-case
+    (let ((pos (curpos it)))
+      (if (< pos (length (data it)))
+        (multiple-value-bind (val newpos) 
+                             (read-from-string (data it) nil nil :start pos)
+          (setf (curpos it) newpos 
+                (value it) val)
+          nil)
+        t))
+    (try-with-more-input (more)
+      (setf (data it) (str:join " " (list (data it) more)))
+      (next it))))
 
 ;;;; stream iterator implementation