If expr is of type typ, the function map(fcn, expr, arg3, ..., argn) is evaluated. Otherwise, $\mathrm{fcn}\left(\mathrm{expr},\mathrm{arg3},...,\mathrm{argn}\right)$ is returned.

$\mathrm{maptype}\left(\mathrm{`+`}\,f\,yz\right)$

$f\left(yz\right)$

$\mathrm{maptype}\left(\mathrm{`+`}\,f\,x+yz\right)$

$f\left(yz\right)+f\left(x\right)$