Bold face formatting for vectors instead of overarrows like latex \mathbf{}?

Question

OverVector can be used to make a symbol look like a vector in text sections of documents. I happen to like bold symbols for vectors better, as in latex \mathbf{x} output.

I've found that I can do, say, Style[x, Bold], but this is actually a very subtle seeming change, and I find it hard to actually notice the difference. Perhaps this is because the default font picked for variables is something quite different from what one gets with \mathbf. If this is just a font issue, what's a good font for this sort of output (i.e. like \mathbf{x}), and how would it be selected?

Also, the Style function applies to expressions, whereas I want it to apply to just particular variables (i.e. leaving scalars in regular font), so that when they are used in input, the output comes out in the desired way.

Is there a mechanism to declare a variable, and have specific style settings associated with it, so that it is displayed in the desired way?

Answer 1

I am not sure I understand your needs, but consider this:

Format[OverVector[v_]] := Style[HoldForm[v], FontFamily -> "Arial Black"]

{q, r, OverVector[s], t, u, v}

Answer 2

This is mainly an add-on to David solution. I'm new in SE, so I can't comment yet. So I put it in an answer.

One could maintain a list of the symbols, which should be displayed as vectors, eg:

vList = {}
defAsVector[x__Symbol] := (vList = Union[Join[vList, {x}]];)
defAsVector[] := vList
undefAsVector[x__Symbol] := (vList = Complement[vList, {x}];)
undefAsVector[] := (vList = {}; $PrePrint =.;)
$PrePrint = # /. {x_ /; MemberQ[vList, x] :> Style[x, Bold]} &;

Answer 3

I only have my iPhone now, but something like this should work well.

MakeBoxes[x,StandardFom]:=StyleBox["x",FontWeight->Bold];  
MakeExpression[StyleBox["x",FontWeight->Bold]]:=MakeExpression["x"].  

Better yet you could 'declare' that certain symbols represent vectors.

declaredVectorQ[x_Symbol]:^=declaredVector[x]^=True;
MakeBoxes[x_Symbol?declaredVectorQ,StandardForm]:=
                                    StyleBox[ToString[x],FontWeight->Bold];  
MakeExpression[StyleBox[str_String,FontWeight->Bold]:=ToExpression[str];

Answer 4

• You can specify a different font by using the FontFamily parameter for Style:

• If you want specific symbols to be printed differently on output, you may want to have a look at $Post and $PrePrint. For example, the following prints the symbol x bold and in Helvetica:

$PrePrint =.
x
$PrePrint = # /. {x -> Style[x, Bold, FontFamily -> "Helvetica"]} &;
x

Be careful though, a styled object can have unwanted side effects. Therefore, in this paragraph, I sincerely disencourage you to change styling of symbols you want to do calculations with, and would recommend doing the prettyprinting in the very end, using an explicit handcoded function.