[gambit-list] |it| in the repl

[Christian]

Hello

Here's a simple patch to make it possible to get the results of
previous evaluations in the repl. (Or have I overlooked an existing
mechanism for that (other than through the serial number)?) It creates
|it| and similar global variables in the default namespace.

What (I think) I would prefer, but don't know how to do, is:

- make those be bound lexically to the code being entered instead, so
that they don't pollute any namespace and don't need any namespace
vodoo to be accessed from the entered code. I imagine that the
variables could be put into the lexical environment of the code being
eval'ed, but simply wrapping with `(let ((it ,old-it)) ,body) wouldn't
do (this would at least break top-level defines).

- make those variables/bindings per-thread, or maybe even
per-repl. (I'd prefer not having to type parens around parameter
objects. But shoveling around the values between lexical context and
internal state or parameter object values would solve this.)

Thanks
Christian.


--- gambc40b17/lib/_repl.scm.1_orig	2006-01-08 19:19:02.000000000 +0100
+++ gambc40b17/lib/_repl.scm	2006-03-03 03:35:09.000000000 +0100
@@ -1771,6 +1771,12 @@
 
   (##exit))
 
+(##namespace ("" it it1 it2 it3))
+(define it #!void)
+(define it1 #!void)
+(define it2 #!void)
+(define it3 #!void)
+
 (define-prim (##repl-within cont write-reason)
 
   (define (with-clean-exception-handling repl-context thunk)
@@ -1943,6 +1949,10 @@
             (macro-repl-context-cont repl-context)
             repl-context
             (lambda (results)
+	      (set! it3 it2)
+	      (set! it2 it1)
+	      (set! it1 it)
+	      (set! it results)
               (##call-with-values
                (lambda ()
                  results)