<!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 6.00.6000.16735" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV>Philip Wadler certainly knows what he is talking about.</DIV> <DIV>I do not fully agrree with his argument about the example</DIV> <DIV>explaining the evaluation of <FONT face="Courier New" size=2>(list (list 1 2) nil)</FONT>, though.</DIV> <DIV>Notice that text in <FONT face="Courier New" size=2>this font</FONT> is implicitly quoted.</DIV> <DIV>I would write:</DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>(list (list 1 2) nil) =</FONT></DIV> <DIV><FONT face="Courier New" size=2>(<FONT face="Times New Roman" size=3>x y</FONT>)<FONT face="Times New Roman" size=3>, where x</FONT> = <FONT face="Times New Roman" size=3>$</FONT>(list 1 2)<FONT face="Times New Roman" size=3> and y</FONT> = <FONT face="Times New Roman" size=3>$</FONT>nil</FONT></DIV> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>(list 1 2) = (1 2)</FONT></DIV> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>nil = ( )</FONT></DIV> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>Hence $</FONT>(list (list 1 2) nil) = ((1 2) ( ))</FONT></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV>where $x is the value of x.</DIV> <DIV>It is a matter of an appropriate distinction between quotation, mention and value.</DIV> <DIV>Other examples:</DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>'x == <FONT face="Times New Roman" size=3>$</FONT>(quote x) = x</FONT></DIV> <DIV><FONT face="Courier New" size=2> <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>list<FONT face="Times New Roman" size=3> is a procedure, not a sexpr. <DIV><FONT face="Courier New" size=2> <DIV><FONT face="Courier New" size=2>list<FONT face="Times New Roman" size=3> is a symbol, but where a non quoted part of a program probably an identifier referring to a variable. <DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>$</FONT>123<FONT face="Times New Roman" size=3> is <FONT face="Courier New" size=2>123</FONT>.</FONT></FONT></DIV> <DIV> </DIV></FONT></FONT></DIV></FONT></DIV> <DIV>With check syntax of DrScheme, the distiction between program and data can clearly be displayed.</DIV> <DIV>In Scheme I like the clear distinction between sexprs and their values.</DIV> <DIV>The fact that some sexprs are self evaluating should not confuse the student, I think.</DIV> <DIV>Jos</FONT></FONT></FONT></DIV></DIV></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV><FONT face="Courier New" size=2>----- Original Message ----- </FONT> <DIV><FONT face="Courier New" size=2>From: "Grant Rettke" <</FONT><A href="mailto:grettke@acm.org"><FONT face="Courier New" size=2>grettke@acm.org</FONT></A><FONT face="Courier New" size=2>></FONT></DIV> <DIV><FONT face="Courier New" size=2>To: "PLT Scheme Mailing List" <</FONT><A href="mailto:plt-scheme@list.cs.brown.edu"><FONT face="Courier New" size=2>plt-scheme@list.cs.brown.edu</FONT></A><FONT face="Courier New" size=2>></FONT></DIV> <DIV><FONT face="Courier New" size=2>Sent: Sunday, November 02, 2008 8:11 PM</FONT></DIV> <DIV><FONT face="Courier New" size=2>Subject: [plt-scheme] Papers on criticism of Scheme?</FONT></DIV></DIV> <DIV><FONT face="Courier New"><BR><FONT size=2></FONT></FONT></DIV><FONT face="Courier New" size=2>> Hi,<BR>> <BR>> This paper:<BR>> <BR>> </FONT><A href="http://www.cs.kent.ac.uk/people/staff/dat/miranda/wadler87.pdf"><FONT face="Courier New" size=2>http://www.cs.kent.ac.uk/people/staff/dat/miranda/wadler87.pdf</FONT></A><BR><FONT face="Courier New" size=2>> <BR>> was referenced recently. It was interesting to see criticisms of<BR>> Scheme from someone who knew Scheme. I think Wadler knew it well.<BR>> <BR>> Are there more like this out there?<BR>> <BR>> Best wishes,<BR>> <BR>> Grant<BR>> _________________________________________________<BR>>  For list-related administrative tasks:<BR>>  </FONT><A href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme"><FONT face="Courier New" size=2>http://list.cs.brown.edu/mailman/listinfo/plt-scheme</FONT></A><BR><FONT face="Courier New" size=2>></FONT></BODY></HTML>