ToExpression to Latex Parenthesis

Question

Everytime I use ToExpression to transform a TeX expression into mathematica input form, Mathematica always interprets parenthesis ('(' and ')') as square brackets, which has a differente meaning for expressions. I always have to manually change the expression. Also, it doesn't happen all the time. Does anybody know what is going on and what can I do to fix this? An Example:

ToExpression["A - \\frac{B (2+F)}{(1+C)} D", TeXForm]

This yields:

A - (D B[2 + F])/(1 + C)

I would like:

A - (D B(2 + F))/(1 + C)

Thanks.

Answer 1

You can use a LaTeX thin space \, as a multiplication symbol to enforce what you want:

ToExpression["A - \\frac{B\\,(2+F)}{(1+C)} D", TeXForm]

(* A-(B D (2+F))/(1+C) *)

As noted by rhermans, standard mathematical notation is ambiguous -- do the parentheses signify multiplication or function arguments? -- so the thin space is needed to remove the ambiguity.

As noted by march, if you want to consistently use parentheses for multiplication, you could define a function like

fromTeX[str_] := ToExpression[StringReplace[str, "(" -> "\\,("], TeXForm]

Now you can do

fromTeX["A - \\frac{B(2+F)}{(1+C)} D"]

(* A - (B D (2 + F))/(1 + C) *)