combine/@@ combines nested functions into function expressions using the iterated composition operator, $\@\@$.

See $\?\@$ for a description of the composition operator.

$\mathrm{combine}\left(f\left(f^{\left(3\right)}\left(x\right)\right)\,\mathrm{`@@`}\right)$

$f^{\left(4\right)}\left(x\right)$

$\mathrm{combine}\left(g\left(g^{\left(4\right)}\left(g^{\left(-2\right)}\left(x\right)\right)\right)\,\mathrm{`@@`}\right)$

$g^{\left(3\right)}\left(x\right)$