Question concerning MakeBoxes

*To*: mathgroup at smc.vnet.net*Subject*: [mg60378] Question concerning MakeBoxes*From*: Cca <cca at gregosetroianos.mat.br>*Date*: Wed, 14 Sep 2005 03:27:58 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Let's start a new Mathematica (5.1) session and note that FormatValues[And] is the empty list. I want to define a rule for formatting logical conjunctions and disjunctionsin in such a way that, for example, the conjunction p&&q&&r is formatted in TraditionalForm as RowBox[{"\[And]", RowBox[{StyleBox["{",SpanMaxSize->\[Infinity]], GridBox[{{"p"},{"q"},{"r"}},ColumnAlignments->{Left}], StyleBox["}",ShowContents->False]}]," "}]//DisplayForm (As far as I know, the idea for this interesting and convenient "grid notation" is due to Bruno BuchBerger, but this is another history.) For me, one obvious solution to this problem should be something like Unprotect[And]; And/:MakeBoxes[And[c__],TraditionalForm]:= RowBox[{"\[And]", RowBox[{StyleBox["{",SpanMaxSize->\[Infinity]], GridBox[{#}&/@(MakeBoxes[#,TraditionalForm]&/@{c}), ColumnAlignments->{Left}], StyleBox["}",ShowContents->False]}]," "}]; Protect[And]; In fact, p&&q&&r//TraditionalForm is now displayed as intended. However, it works only once: evaluating again p&&q&&r//TraditionalForm gives the built-in traditional formatting. After inspecting FormatValues[And] we see what is going on: my formatting rule is the LAST on the list. So, in order to force Mathematica to apply my definition first, I evaluate Unprotect[And]; FormatValues[And]=Reverse@FormatValues[And]; Protect[And]; This solves my problem, but in a somewhat inelegant way. My questions are: (1) what is the explanation for this behavior? (2) how can I get the intended result without reversing FormatValues[And]? My anticipated thanks for any help. Carlos César de Araújo Gregos & Troianos Educacional www.gregosetroianos.mat.br Belo Horizonte, MG, Brazil (31) 3283-1122