lib/lasp/stdmacros.lasp in lasp-0.8.0 vs lib/lasp/stdmacros.lasp in lasp-0.9.0

@@ -6,18 +6,49 @@
 (def defm
   (macro (name params body)
          (list 'def name
                (list 'macro params body))))
 
+
 ; Shorthand for defining functions
 ;
 ;   (defn f (x) (+ x 1))
 ; expands to:
 ;   (def f (fn (x) (do (+ x 1))))
 (defm defn
   (name params & body)
   (list 'def name
         (list 'fn params (cons 'do body))))
+
+
+; Creates local bindings.
+;
+; It does this by (ab)using closures. It rewrites the form as a recursively
+; nested tree of functions, declaring parameters and instantly executing the
+; function passing in corresponding arguments. This should be considered an
+; implementation detail, let can (and should) be used without knowledge or
+; regard to that it creates closures behind the scenes.
+
+; Example:
+;     (let (one 1
+;           two (+ one 1)) ; Previous bindings are available
+;       (+ one two))
+;     ; => 3
+;
+; expands to:
+;     ((fn (one) ((fn (two) (do (+ one two))) (+ one 1))) 1)
+(defn let*
+  (bindings body)
+  (if (empty? bindings)
+    (cons 'do body)
+    (list
+      (list 'fn (list (first bindings)) (let* (drop 2 bindings) body))
+      (second bindings))))
+
+(defm let
+  (bindings & body)
+  (let* bindings body))
+
 
 ; See unevaluated form the macro expands to for debugging macros
 ;
 ; This simply uses the fact that `apply` already has this effect
 ; of expanding macros and makes the syntax a bit nicer, you can