Scope modifiers: Difference between revisions

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@@ Line 184: / Line 184: @@
 (let ((shape "triangle") (*bug* "ant"))
-  (defun speak ()
+  (flet ((speak ()
-    (format t "~%  There is some ~A in my ~A!" *bug* shape))
+           (format t "~%  There is some ~A in my ~A!" *bug* shape)))
-  (format t "~%Put ~A in your ~A..." *bug* shape)
+    (format t "~%Put ~A in your ~A..." *bug* shape)
-  (speak))
+    (speak)
+    (let ((shape "circle") (*bug* "cockroach"))
+      (format t "~%Put ~A in your ~A..." *bug* shape)
+      (speak))))</lang>
+The function <code>speak</code> tries to use both <code>*bug*</code> and <code>shape</code>. For lexical scope, the value comes from where the program ''defines'' <code>speak</code>. For dynamic scope, the value comes from where the program ''calls'' <code>speak</code>. So <code>speak</code> always uses the same "triangle", but can use a different bug.
-(let ((shape "circle") (*bug* "cockroach"))
-  (format t "~%Put ~A in your ~A..." *bug* shape)
-  (speak))</lang>
-The global function <code>speak</code> tries to use both <code>*bug*</code> and <code>shape</code>. For lexical scope, the value comes from where the program ''defines'' <code>speak</code>. For dynamic scope, the value comes from where the program ''calls'' <code>speak</code>. So <code>speak</code> always uses the same "triangle", but can use a different bug.
 <pre>Put ant in your triangle...