<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.6000.16788" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face="Courier New" size=2>My question is at the <===== in the following code:</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>(define-syntax (x stx)<BR> (syntax-case stx ()<BR>  ((_ x)<BR>   (let ((y (expand-once #'x)))<BR>    (printf "~s~n" (syntax->datum y))<BR>    (syntax-case y (#%app)<BR>     ((#%app . z) #''app)<BR>     (_ #''no-app))))))</FONT></DIV> <DIV> </DIV> <DIV><FONT face="Courier New" size=2>(x (let ((a 1)) a))<BR>; printed: (let-values (((a) 1)) a)<BR>; value: no-app, ok<BR>(x (list 1 2 3))<BR>; printed (#%app list 1 2 3)<BR>; value: no-app, why??? <===== I expected app<BR>(x list)<BR>; printed: list<BR>; value: no-app, ok</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>Thanks, Jos</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV></BODY></HTML>