Download the file a2-money.zip in Assignments in the SVN. Instructions are in the PDF file W09-a2-money-spec.pdf.

Since your code will be executed and checked with a script, you must follow the instructions precisely. Your work is in a directory a2-money (with ecf file as is, in this folder). You must do a written report which you must include in this directory.

Before submitting, eclean and do a fresh compile and execute to make sure that you get a green bar. Then eclean the directory a2-money again (to get rid of the EIFGEN's) and submit it:

 submit -l 3311 a2 a2-money

Don't forget to also hand in your written report at the 3311 drop box in the CSE building.

• We would like to use HASH_TABLE[G, H] to implement the efficient version of MAP when we can rely on hashable keys.
• Eiffelstudio 6.3 is in transition to implementing void safety (which means that the compiler will always catch errors of the type t.f(x) where t = Void). As part of the transition, a type with a question mark in front of it (?T) is detachable (allowed to be Void) whereas a type with an exclamation mark (!T) is an attached type (is never allowed to be void).
• The latest version of HASH_TABLE inherits from TABLE [?G, ?K], i.e. the generic parameters are allowed to be attached to Void. So, to use HASH_TABLE in HASHABLE_MAP, we can proceed as follows:

class 
   HASHABLE_MAP [KEY -> {HASHABLE,COMPARABLE}, VAL]
inherit
   MAP[?KEY,?VAL] 
create
   make
feature 
   has (k: ?KEY):BOOLEAN  ...
 
   item alias "[]" (k: ?KEY): ?VAL assign override ...
 
   has_tuple(t: TUPLE[k:?KEY; v:?VAL]): BOOLEAN ...
 
   domain: ARRAY[?KEY]
 
feature{NONE}
   map_imp: HASH_TABLE[VAL, KEY]
end

The question mark will ensure that the keys and values can be Void. you may sometimes have to do the following to obtain the correct types:

t: TUPLE[KEY,VAL]
 
t ?= [map_imp.key_for_iteration, map_imp.item_for_iteration]

“?=” is assignment attempt and is discussed in the text book OOSC2.