New special operator: compiler-let

* eval.c (compiler_let_s): New symbol variable.
(op_let): Recognize compiler-let for sequential
binding.
(do_expand): Traverse and diagnose compiler-let
form.
(eval_init): Initialize compiler_let_s and register
the interpreted version of the operator.

* stdlib/compiler.tl (compiler compile): Handle
compiler-let form.
(compiler comp-compiler-let): New method.
(no-dvbind-eval): New function.

* autoload.c (compiler-set-entries): Intern the
compiler-let symbol in the user package.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.

1 files changed, 10 insertions, 0 deletions

diff --git a/stdlib/compiler.tl b/stdlib/compiler.tl
index cc4eef7b..504d3ea8 100644
--- a/stdlib/compiler.tl
+++ b/stdlib/compiler.tl
@@ -564,6 +564,7 @@
               ((+ *) me.(comp-arith-form oreg env form))
               ((- /) me.(comp-arith-neg-form oreg env form))
               (typep me.(comp-typep oreg env form))
+              (compiler-let me.(comp-compiler-let oreg env form))
               (t me.(comp-fun-form oreg env form))))
            ((and (consp sym)
                  (eq (car sym) 'lambda)) me.(compile oreg env ^(call ,*form)))
@@ -1390,6 +1391,12 @@
     (@nil
      me.(comp-fun-form oreg env form))))
 
+(defmeth compiler comp-compiler-let (me oreg env form)
+  (tree-bind (t bindings . body) form
+    (progv [mapcar car bindings]
+           [mapcar [chain cadr no-dvbind-eval] bindings]
+           me.(comp-progn oreg env body))))
+
 (defmeth compiler comp-fun-form (me oreg env form)
   (let* ((olev *opt-level*)
          (sym (car form))
@@ -2306,6 +2313,9 @@
   (member (symbol-package sym)
           (load-time (list user-package system-package))))
 
+(defun no-dvbind-eval (form)
+  (eval (if-match (sys:dvbind @nil @exp) form exp form)))
+
 (defun usr:compile-toplevel (exp : (expanded-p nil))
   (let ((co (new compiler))
         (as (new assembler))