iterator - Eiffel Iterable implementation on MAP? -

iterator - Eiffel Iterable implementation on MAP? -

i have class called map :

class map [key,val] inherit iterable [key]

i implemented new cursor within map cursor returns ,

map_iterator_cursor [key]

and passes iterable cursor array of keys iterate through

i implemented map_iterator_cursor [key] class

class map_iterator_cursor [key] inherit iteration_cursor [key]

for class implemented feature item: val because class defined key won't recognize val how map_iterator_cursor [key] item feature homecoming val associated key on @ moment ?

knowing map has function called item take key , returns val associated key

item (k: key): val

as map [key, val] inherits iterable [key], generic parameter of iteration_cursor bound key. {iteration_cursor}.item normal feature, subject redeclaration, renaming, etc. hence several approaches can fit need:

declare map_iterator_cursor have 2 formal generics , declare {map}.new_cursor follows:

class map [key, val] inherit iterable [key] feature new_cursor: map_iterator_cursor [key, val] create result.make (current) end end class map_iterator_cursor [key, val] inherit iteration_cursor [key] create create feature create (t: target) target := t end target: map [key, val] item: key ... value: val result := target.item (item) end end

then client code can as

across map c loop -- utilize `c.item` of type key. -- utilize `c.value` of type val. end

if required {map_iterator_cursor}.item of type val, first way utilize same code above rename feature item comes iterable:

class map_iterator_cursor [key, val] inherit iteration_cursor [key] rename item key end ... key: key ... item: val result := target.item (key) end end

then client code can as

across map c loop -- utilize `c.item` of type val. -- utilize `c.key` of type key. end

the iteration can performed on items of type val beginning. in case actual generic of iterable should val:

class map [key, val] inherit iterable [val] feature new_cursor: map_iterator_cursor [key, val] create result.make (current) end end class map_iterator_cursor [key, val] inherit iteration_cursor [val] create create feature create (t: target) target := t end target: map [key, val] item: val result := target.item (key) end key: key -- feature can not exported, or not nowadays -- `item` can implemented. end

the client code similar case 2, key may unavailable:

across map c loop -- utilize `c.item` of type val. end

in 3 formal generic key in map_iteration_cursor kept convenience. can removed provided there way access items of map, may raise other issues related access map, conformance , cat-calls. hence though it's potentially feasible, not go it.

iterator iterable eiffel