Add support for named (let ...) forms. (Does not yet include let* or letrec.)

libcompiler/simplifier.scm

@@ -100,6 +100,8 @@
        (iter rst (cons (list var expr) bindings))]
       [`((define . ,_) . ,_)
        (error "Unrecognized define-form:" (first body))]
+      [`((begin . ,forms) . ,rst)
+       (iter (append forms rst) bindings)]
       [`(,form . ,rst)
        (if (null? bindings)
            (cons form (iter rst '()))
@@ -175,6 +177,22 @@
        ,@(filter-map second bindings)
        (,simple-op ,@(map first bindings)))))
 
+; (let name ([var expr]...) bodyexpr...)
+;    => ((letrec ([name (lambda (var...)
+;                         bodyexpr...)])
+;          name) expr...)
+
+(define (simplify-named-let form)
+  (define (expand-binding binding)
+    (if (pair? binding) binding (list binding '#%undef)))
+  (define let-name (second form))
+  (define bindings (map expand-binding (third form)))
+  (define bodyexprs (body->forms (cdddr form)))
+
+  (simplify-form
+   `((letrec ([,let-name (lambda ,(map first bindings) ,@bodyexprs)]) ,let-name)
+     ,@(map second bindings))))
+
 ; (let ([var expr]...) bodyexpr...)  ; first eval exprs, then assign bindings in parallel
 ;    => (#%bind (tmp...)
 ;         (#%set! tmp ,(simplify-form expr))...
@@ -182,7 +200,7 @@
 ;           (#%set! var tmp)...
 ;           bodyexpr...))
 
-(define (simplify-let form)
+(define (simplify-unnamed-let form)
   (define (simplify-binding binding)
     (if (pair? binding)
       (list (first binding) (simplify-form (second binding)))
@@ -215,6 +233,11 @@
               (filter has-value? bindings))
        ,@(map simplify-form bodyexprs))))
 
+(define (simplify-let form)
+  (if (symbol? (second form))
+      (simplify-named-let form)
+      (simplify-unnamed-let form)))
+
 ; (let* ...)   ; eval exprs & bind variables serially
 ;    => (let ([var-0 expr-0])
 ;         (let ([var-1 expr-1])