function - removing alternating elements on a list in scala -

i trying write recursive function in scala takes in list of strings , returns list alternating elements original list:

for example:

list = {"a","b","c"} list b = {"a","c"}

the head should included.

def removealt(list:list[string], str:string):list[string]=lst match{  case nil=> list() case => head::tail if(head == true)    removealternating(list,head) else    head::removealternating(list,head) 

i stack overflow error.

i understand code incorrect trying understand logic on how accomplish recursion , no built in classes.

def remove[a](xs:list[a]):list[a] = xs match {     case nil => nil     case x::nil => list(x)     case x::y::t => x :: remove(t)     }   

if list empty, return empty list. if we're @ last element of list, return that. otherwise, there must 2 or more elements. add first element alternate elements of rest of list (and omit second element)