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From: yogesh on 23 Apr 2008 16:04
Hi,

I need to know how to solve this problem of the code ,

kindly help me if any one know this
given 2 classes A and B defined as follows
struct A { int a; }
struct B { int b; char c; }
the requirement is to efficiently write 2 map classes
1. class AMap
It should have member functions similar to below
add (const std::string name, A*)
A* get (const std::string name)
remove(const std::string name)
2. class BMap
It should have member functions similar to below
add (const std::string name, B*)
B* get (const std::string name)
remove(const std::string name)
Note that in the above add/get/remove functions, I have
deliberately not provided the correct signatures as that is what you
need to create.
Add a main routine that exercises all the above functions
no extra libs like glib should be used; STL may be used


can any one guess what this

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From: Nicola Musatti on 24 Apr 2008 06:18
On Apr 24, 9:04 am, yogesh <yogeshkum...(a)gmail.com> wrote:
> Hi,
>
> I need to know how to solve this problem of the code ,
[...]
> can any one guess what this

I'll venture a guess: this is homework! If I'm correct you should try
and solve the problem by yourself and come back for advice on
specific, concrete issues, rather than look for people to do it for
you.

If I'm mistaken, well, a good way to prove me wrong is to follow my
advice above ;-)

Cheers,
Nicola Musatti

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From: Alf P. Steinbach on 24 Apr 2008 06:43
* yogesh:
>
> I need to know how to solve this problem of the code ,

I'm not sure how this one slipped past moderation, but the moderators
(praise be
upon them![1] :-)) are only human.

This is clearly homework and as such, the article should have been rejected.

Note that if you don't do your homework yourself, but just ask others to do
it,
you will only be postponing the point where you're unable to proceed with
the
course (or some other course). And on the way you will then have wasted
other's
time and money, namely those helping you, and your own or your family's
money,
because instead of paying tuition and not earning wages and then failing the

course or some later course, you could have been working /earning/ money.
Also,
please don't post the same article independently to many newsgroups, because

that is an additional waste of time for those wishing to help you, and for
readers.


> kindly help me if any one know this
> given 2 classes A and B defined as follows
> struct A { int a; }
> struct B { int b; char c; }
> the requirement is to efficiently write 2 map classes
> 1. class AMap
> It should have member functions similar to below
> add (const std::string name, A*)
> A* get (const std::string name)
> remove(const std::string name)
> 2. class BMap
> It should have member functions similar to below
> add (const std::string name, B*)
> B* get (const std::string name)
> remove(const std::string name)
> Note that in the above add/get/remove functions, I have
> deliberately not provided the correct signatures as that is what you
> need to create.

The above paragraph is a message from your teacher to you. He or she is
hinting
that the signatures are not perfect. Consider references instead of
pointers.


> Add a main routine that exercises all the above functions
> no extra libs like glib should be used; STL may be used

If you can use "STL", presumably meaning the C++ standard library, then one
way
to cheat would be to use std::map. However, I'm sure your teacher meant
that
you could use the standard C++ library in your test program, and that you
should
not use std::map in the implementation of the two classes AMap and BMap.

Essentially your teacher is asking you to create two classes AMap and BMap
akin
to std::map, except not as a template class that can handle any kinds of
keys
and values, but just handling strings as keys, and A and B as values. The
requirement of "efficiently" probably means that a linear search for a key
is
not sufficient except as an optimization for small number of keys. The
general
search must use e.g. a binary search or a hash table lookup.

Presumably the intent is to then let you realize that the two classes AMap
and
BMap are (or could be) identical except for the value type that a key
retrieves,
and then to introduce you to templates, where instead of two distinct
classes
AMap and BMap you can just write one general template class, like std::map.


Cheers, & hth.,

- Alf


Notes:
[1] We do receive praise for our work, thank you all. Also many many thanks
to
those who report problems. Without knowing about problems we can't fix
them.

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From: red floyd on 24 Apr 2008 06:43
yogesh wrote:
> ["do my homework"] redacted.

Please find your answer in the FAQs at
http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.2

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From: Stuart Golodetz on 24 Apr 2008 06:43
yogesh wrote:
> Hi,
>
> I need to know how to solve this problem of the code ,
>
> kindly help me if any one know this
> given 2 classes A and B defined as follows
> struct A { int a; }
> struct B { int b; char c; }
> the requirement is to efficiently write 2 map classes
> 1. class AMap
> It should have member functions similar to below
> add (const std::string name, A*)
> A* get (const std::string name)
> remove(const std::string name)
> 2. class BMap
> It should have member functions similar to below
> add (const std::string name, B*)
> B* get (const std::string name)
> remove(const std::string name)
> Note that in the above add/get/remove functions, I have
> deliberately not provided the correct signatures as that is what you
> need to create.
> Add a main routine that exercises all the above functions
> no extra libs like glib should be used; STL may be used
>
>
> can any one guess what this

Yes, he wants you to write two classes which map strings to A* and B*
respectively. I don't think the way he's specified it is especially
precise, and I'm not sure A* and B* are especially good choices for a
value type (who owns the memory pointed to? who should ultimately
delete/free it?), but those are things you can point out in your answer.
It's also worth asking what he means by "efficiently write". Should the
writing be efficient, or the code? There's not always a trade-off
involved, but there can be.

Regards,
Stu

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