As an example for why an abbreviated traditional form is important to
have, consider the following example from vector analysis.
Needs["VectorAnalysis`"];
SetCoordinates[Cartesian[x, y, z]];
a = Through[Array[
\!\(\*SubscriptBox[\("\<A\>"\), \({"\<x\>", "\<y\>", \
"\<z\>"}[\([\)\(#\)\(]\)]\)]\) &, 3][x, y, z]];
b = Through[Array[
\!\(\*SubscriptBox[\("\<B\>"\), \({"\<x\>", "\<y\>", \
"\<z\>"}[\([\)\(#\)\(]\)]\)]\) &, 3][x, y, z]];
MatrixForm[a]
MatrixForm[b]
Prove explicitly the following theorem which Mathematica tells us is
true:
Simplify[Curl[a\[Cross]b] ==
a Div[b] - b Div[a] + Map[b.Grad[#] &, a] - Map[a.Grad[#] &, b]]
It is nice that Mathematica says it's true, but we want to explain it
to our readers by going step by step. Unfortunately, writing out the
vectors is quite cumbersome. Even the left-hand side is already quite
long (not to mention the right side):
Curl[a\[Cross]b]
All this becomes much easier with the simplified traditional form, in
conjunction with some formatting specific to my problem:
Derivative /:
MakeBoxes[Derivative[\[Alpha]__][f1_][vars__Symbol],
TraditionalForm] :=
Module[{bb, dd, sp},
MakeBoxes[dd, _] ^=
If[Length[{\[Alpha]}] == 1, "\[DifferentialD]", "\[PartialD]"];
MakeBoxes[sp, _] ^= "\[ThinSpace]";
bb /: MakeBoxes[bb[x__], _] := RowBox[Map[ToBoxes[#] &, {x}]];
FractionBox[ToBoxes[bb[dd^Plus[\[Alpha]], f1]],
ToBoxes[Apply[bb,
Riffle[Map[bb[dd, #] &,
Select[({vars}^{\[Alpha]}), (# =!= 1 &)]], sp]]]]]
nice[expression_] :=
Module[{f, i, x},
HoldForm[expression // MatrixForm] /.
Subscript[f_, i_][x__] -> Subscript[f, i] // TraditionalForm]
The left-hand side of my desired equation is now:
Curl[a\[Cross]b] // nice
With this, you can now compare terms and recognize cancellations, etc.
So not everything is best done in StandardForm, and there is clearly a
place for a concise TraditionalForm.
Jens