topical slide(s): creative technology / new media / game development(s)

Behavioral subtypes

$stack <= bag$

bag -- put, get
stack -- push, pop, settop

Representation

bag -- $<< elems, bound >>$ \zline{multiset}
stack -- $<< items, limit >>$ \zline{sequence}

Behavior -- put/push


   $put(i):$ 
     $require   size( b.elems ) < b.bound$ 
     $promise   b' = << b. elems \uplus { i }, b.bound >>$ 
  
   $push(i):$ 
     $require   length( s.items ) < s.limit$ 
     $promise   s' = << s.items \. i, s.limit >>$

slide: Behavioral subtypes -- example