 
 
 
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 :
 
 
