Lukas-Fabian Moser <l...@gmx.de> writes: > Hi Luca, > > without having tested your code: You're using append! wrong. > > From the Guile documentation: "append! is permitted, but not required, to > modify the given lists to form its return." > So the exclamation mark does not imply that your list gets modified > in-place, but rather that you don't care whether or not append! changes > your original list. So try > > (set! fl (append fl ...)) > > where you could probably also use append! instead of append (I imagine it > might be more efficient).
Most pertinent: (append! '() ...) cannot modify an empty list in-place because there is only one empty list in the whole system and it is an unchangeable constant. Indeed Guile happens to modify the given list in-place with append! whenever it can, but it is impossible for the empty list. -- David Kastrup
