Apply a terra function that takes only a single layer to all layers
Apply to all layers of a SpatRaster a function that only takes a single layer SpatRaster (these are rare). 
in most cases you can also use lapply or sapply for this.
## S4 method for signature 'SpatRaster' sapp(x, fun, ..., filename="", overwrite=FALSE, wopt=list())
| x | SpatRaster | 
| fun | a function that takes a SpatRaster argument and can be applied to each layer of  | 
| ... | additional arguments to be passed to  | 
| filename | character. Output filename | 
| overwrite | logical. If  | 
| wopt | list with named options for writing files as in  | 
SpatRaster
s <- rast(system.file("ex/logo.tif", package="terra")) + 1  
x <- sapp(s, terrain)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.