5.40.22  Remove elements of a list : remove

remove takes as argument : a boolean function f and a list L.
remove removes in the list L, the elements c such that f(c)==true.
Input :

Output :

Remark The same applies on strings, for example, to remove all the "a" of a string:
Input :

Output :

Input :

f(chn):={
  local l:=length(chn)-1;
  return remove(x->(ord(x)==97),seq(chn[k],k,0,l));
}

Then, input :

Output :

To get a string, input :

Output :