add comment to fprintf
Merge branch 'master' into structs
add W_Cell to store mutable data
move creating W_Cell into set method
add support of prop:arity-string
add some prefab functionality
Merge branch 'master' into structs
Merge branch 'master' into structs
add assert to check type of the prefab's name
Merge branch 'master' into structs
Merge branch 'master' into structs
add prefabs
create prefab structure type together with a struct instance
Merge branch 'master' into structs
add OutputFormatter for fprintf (multiple replace without regex)
add build-in exception types (the constructor, predicate, and accessors)