# LaTeX equivalent to MahtML's &ApplyFunction;

Here is a question that has long been bothering me: what is the correct way to write a function application in \LaTeX?

The simple answer is of course $f(x)$. However, $f\left(x\right)$ delivers a different result (in terms of spacing), even if the height of the argument does not require larger brackets.

In MathML, &ApplyFunction; controls the spacing between the function and its argument like so <mi>f</mi><mo>&ApplyFunction;</mo><mfenced<mi>x</mi></mfenced>.

Is there a similar construct in LaTeX?

Thanks, Sébastien

• I think the mathtools package fixes the spacing discrepancy between f(x) and f\left(x\right), but I can't find a reference right now. – Arun Debray Nov 9 '16 at 16:35
• @ArunDebray, mathtools does not help in this case. If you insist on using left/right (I would not) then you need \mleft/mright (mleftright package). That case that mathtools does fix, is when a fencing macro is made using \DeclarePairedDelimiter  then the auto scaller is "fixed", but that is not general. – daleif Nov 9 '16 at 18:55

Insert \!, this is a negative space exactly equal to the extra space that is inserted between f and \left(. If necessary also at the end.
$f\!\left(x\right)\!$