add define lambda shorthandHEADmaster

2 files changed, 19 insertions, 7 deletions

diff --git a/environment.scm b/environment.scm
index 37f9fa4..d5e606d 100644
--- a/environment.scm
+++ b/environment.scm
@@ -29,7 +29,7 @@
       (error "Too few or too many arguments supplied" vars vals)))
 
 ;;; variable lookup
-(define (is-unassigned? u) (eq? u '*unassigned*))
+(define (is-unassigned? u) (eq? u ''*unassigned*))
 (define (lookup-variable-value var env)
   (cond
     [(empty-env? env) (error "Unbound variable" var)]
@@ -77,6 +77,5 @@
                        the-empty-env)])
     (define-variable! 'true #t initial-env)
     (define-variable! 'false #f initial-env)
-    (define-variable! '*unassigned* #f initial-env)
     initial-env))
 
diff --git a/main.scm b/main.scm
index 1781255..bc7c862 100644
--- a/main.scm
+++ b/main.scm
@@ -71,6 +71,17 @@
 (define (definition? expr) (tagged? expr 'define))
 (define (definition-name expr) (cadr expr))
 (define (definition-value expr) (caddr expr))
+(define (definition-lambda? expr) (pair? (definition-name expr)))
+(define (definition-lambda-name expr) (caadr expr))
+(define (definition-lambda-params expr) (cdadr expr))
+(define (definition-lambda-body expr) (cddr expr))
+(define (make-definition name value) (list 'define name value))
+(define (definition->lambda expr)
+  (let ([name (definition-lambda-name expr)]
+        [params (definition-lambda-params expr)]
+        [body (definition-lambda-body expr)])
+    (make-definition name
+                     (make-lambda params body))))
 
 ;;; lambda
 (define (lambda-form? expr) (tagged? expr 'lambda))
@@ -134,7 +145,7 @@
        statements))
 (define (make-unassigned-bindings internal-defines)
   (map (lambda (d)
-         (list (definition-name d) '*unassigned*)) internal-defines))
+         (list (definition-name d) ''*unassigned*)) internal-defines))
 (define (scan-out-defines body)
   (let ([internal-defines (filter definition? body)]
         [rest (filter (lambda (n) (not (definition? n))) body)])
@@ -197,10 +208,12 @@
     env))
 
 (define (eval-definition expr env)
-  (define-variable! 
-    (definition-name expr)
-    (eval-expr (definition-value expr) env)
-    env))
+  (cond
+    [(definition-lambda? expr) (eval-expr (definition->lambda expr) env)]
+    [else (define-variable! 
+            (definition-name expr)
+            (eval-expr (definition-value expr) env)
+            env)]))
 
 (define (eval-function-application expr env)
   (let ([proc (operator expr)]