A (almost) simple Lisp reader

[jscl.git] / lispstrack.lisp

diff --git a/lispstrack.lisp b/lispstrack.lisp
index 794e082..c352d71 100644 (file)
--- a/lispstrack.lisp
+++ b/lispstrack.lisp
@@ -1,13 +1,80 @@
-(defun ls-compile (sexp)
+;;; Utils
+
+;;; simplify me, please
+(defun concat (&rest strs)
+  (reduce (lambda (s1 s2) (concatenate 'string s1 s2))
+          strs
+          :initial-value ""))
+
+
+(let ((counter 0))
+  (defun make-binding (symbol)
+    (cons symbol (format nil "V_~d" (incf counter)))))
+
+;;; Compiler
+
+(defvar *compilations* nil)
+
+(defun extend-env (args env)
+  (append (mapcar #'make-binding args) env))
+
+(defun ls-lookup (symbol env)
+  (let ((binding (assoc symbol env)))
+    (if binding
+       (format nil "~a" (cdr binding))
+       (error "Undefined variable `~a'"  symbol))))
+
+(defmacro define-compilation (name args &body body)
+  "creates a new primitive `name' with parameters args and @body. The
+body can access to the local environment through the variable env"
+  `(push (list ',name (lambda (env ,@args) ,@body))
+         *compilations*))
+
+(define-compilation if (condition true false)
+  (format nil "((~a)? (~a) : (~a))"
+          (ls-compile condition env)
+          (ls-compile true env)
+          (ls-compile false env)))
+
+(define-compilation lambda (args &rest body)
+  (let ((new-env (extend-env args env)))
+    (concat "(function ("
+           (format nil "~{~a~^, ~}" (mapcar
+                                     (lambda (x) (ls-lookup x new-env))
+                                     args))
+           "){ "
+           (ls-compile-block body new-env)
+           "})
+")))
+
+(define-compilation setq (var val)
+  (format nil "~a = ~a" (ls-lookup var env) (ls-compile val env)))
+
+(define-compilation quote (sexp)
   (cond
-    ((symbolp sexp) nil)
-    ((integerp sexp) (format nil " ~a " sexp))
-    ((stringp sexp) (format nil " \"~a\" " sexp))
-    ; list
-    ((case (first sexp)
-       (if nil)
-       (lambda nil)
-       (t nil)))))
+    ((integerp sexp) (format nil "~a" sexp))
+    ((stringp sexp) (format nil "\"~a\"" sexp))
+    ((listp sexp)   (format nil "[~{~a~^, ~}]" sexp))))
 
-(defparameter *env-var* '())
+(defparameter *env* '())
 (defparameter *env-fun* '())
+
+(defun ls-compile (sexp &optional env)
+  (cond
+    ((symbolp sexp) (ls-lookup sexp env))
+    ((integerp sexp) (format nil "~a" sexp))
+    ((stringp sexp) (format nil " \"~a\" " sexp))
+                                       ; list
+    ((listp sexp)
+     (let ((compiler-func (second (assoc (car sexp) *compilations*))))
+       (if compiler-func
+           (apply compiler-func env (cdr sexp))
+           ;; funcall
+           )))))
+
+(defun ls-compile-block (sexps env)
+  (format nil
+    "~{~#[~; return ~a;~:;~a;~%~]~}"
+    (mapcar #'(lambda (x)
+                     (ls-compile x env))
+                 sexps)))