{def S.in
 {def S.in.r {lambda {:c :w :i :n}
  {if {= :i :n}
   then -1
   else {if {W.equal? :c {W.get :i :w}}
   then :i
   else {S.in.r :c :w {+ :i 1} :n}}}}}
 {lambda {:c :w}
  {S.in.r :c :w 0 {W.length :w}}}}
-> S.in



{def startswith
 {lambda {:w1 :w2}
  {= {S.in _ {S.replace :w2 by _ in :w1}} 0}}}
-> startswith

{def endswith
 {lambda {:w1 :w2}
  {= {S.in _ {S.replace :w2 by _ in :w1}}
     {- {W.length :w1} {W.length :w2}}}}}
-> endswith

{def isin
 {lambda {:w1 :w2}
  {S.in _ {S.replace :w2 by _ in :w1}}}}
-> isin

{startswith nabuchodonosor nabu}
-> true
{startswith nabuchodonosor abu}
-> false

{endswith nabuchodonosor sor}
-> true
{endswith nabuchodonosor oso}
-> false

{isin nabuchodonosor oso}
-> 10   // is in at 10
{isin nabuchodonosor xyz}
-> -1   // is not in