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DATE 2011-05-01

HANGOUT

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Key: Value:

Key: Value:

MESSAGE
DATE 2011-05-26
FROM Ruben Safir
SUBJECT Subject: [ruben@mrbrklyn.com: Re: [NYLXS - HANGOUT] C++ Workshop - New
----- Forwarded message from Ruben Safir -----

Date: Wed, 25 May 2011 17:10:40 -0400
From: Ruben Safir
To: Ruben Safir
Cc: nylug-talk-at-nylug.org, mrbrklyn-at-panix.com
Subject: Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
Tuesday Night
User-Agent: Mutt/1.5.20 (2009-06-14)

n Monday 23 May 2011 16:37:36 Ruben Safir wrote:
> I'm having trouble understanding why my program is making a change in
> the argument type of my template class function
>
> template < class T >
> void List::find_value(T val)

...
> I then pass int search_val to method
> chainlist::List::find_value(T)
> where T = stats::Distribution (where T is an int) on this line:
>
> dump->find_value(search_val);
>
> and that's where the weirdness happens. I have a type mismatch
> since
> I'm sending by value an integer instead of a stats::Distribution

< Out of curiosity, is this typcastable? e.g.:

dump->find_value((stats::Distribution)search_val);>

That is exactly the type that the function takes in the context of the
calling, class. T is an int. The issue winds up being that of
implicit conversion which happens if there is a stats::Distirbution
single argument constructor. For this to happen, the Template argument
needs to be specifically defined, which it is in this case since it was
defined in the class.



<< [function for reference: void List::find_value(T val) ]

I think this is a case where the compiler needs help, because
find_value() is
looking for a templated generic value, so the compiler doesn't
know that it
can't send in a simple integer. The whole purpose of using
templates is to
keep the type abstract, so I'm not sure how you'd solve this
within the
function header. >>

As it turns out, this is an explicit rule. If T is not defined, the
implicit conversion can not happen a`nd it is considered, "Can not be
deduced".

o


<<
I've been trying to read your C++ code, but I've been finding
it difficult;
the stream of templated objects... wow. However in the middle
of trying to
read things that I can parse, I noticed the following:
>>

Well, it's an excersize in templates. Your familiar with the rules for
vector<> and list<> because they are part of the standard template
libray. My chainlist::List seems to be pretty decent at this point, but
the syntax is unknown unless you pour over the code *List<>->cursor()
returns a chainlist::Node class object. It contains a pointer to a
value of type T and a pointer to the Next Node

Things get exciting when T is its own class.

<< float mean_list( )
...
while(tallies->cursor() != tallies->endd() ){
...
if(dump->cursor() != NULL)
...
}
...
if(dump->cursor() != 0)

If dump->cursor() is a pointer, then compare it with NULL, not 0.
>>

There is a lot of debate on this issue. Strausoup strongly urges 0,
but frankly, dealing with nulls in C++ is a PIA, and even moreso now
with the new standard which blows a warning at you if you assign NULL
to an int type variable.

<< Even if
this works, I'd choose one test and try to stick to it for
readability
reasons.
>>

Ruben


-- Chris

--
Chris Knadle
Chris.Knadle at coredump.us



--
http://www.mrbrklyn.com - Interesting Stuff
http://www.nylxs.com - Leadership Development in Free Software

So many immigrant groups have swept through our town that Brooklyn, like Atlantis, reaches mythological proportions in the mind of the world - RI Safir 1998

http://fairuse.nylxs.com DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002

"Yeah - I write Free Software...so SUE ME"

"The tremendous problem we face is that we are becoming sharecroppers to our own cultural heritage -- we need the ability to participate in our own society."

"> I'm an engineer. I choose the best tool for the job, politics be damned.<
You must be a stupid engineer then, because politcs and technology have been attached at the hip since the 1st dynasty in Ancient Egypt. I guess you missed that one."

? Copyright for the Digital Millennium

----- End forwarded message -----

  1. 2011-05-02 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  2. 2011-05-06 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] NYLXS Business
  3. 2011-05-06 Ron Guerin <ron-at-vnetworx.net> Re: [NYLXS - HANGOUT] NYLXS Business
  4. 2011-05-06 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] NYLXS Business
  5. 2011-05-09 Ron Guerin <ron-at-vnetworx.net> Subject: [NYLXS - HANGOUT] UPDATED! NYLUG Presents: 5/18 -at- 6:30PM Cameron L. Fadjo on Construct, Program, Design: An Introduction to Scratch From the Perspective of Computing and Cognition
  6. 2011-05-09 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - Notes
  7. 2011-05-10 Ron Guerin <ron-at-vnetworx.net> Subject: [NYLXS - HANGOUT] NYLUG Workshop / Hacking Society (Smalltalk, C++, Python) Tuesday May 10 6:00PM-8:00PM
  8. 2011-05-15 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - Notes
  9. 2011-05-16 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - Notes
  10. 2011-05-16 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Fwd: [New-York-C-Developers-Group] MongoNYC - MongoDB Conference
  11. 2011-05-16 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  12. 2011-05-18 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [rick-at-linuxmafia.com: [conspire] YouTube downloading software
  13. 2011-05-19 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - creating a distribution list
  14. 2011-05-19 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - creating a distribution list
  15. 2011-05-20 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  16. 2011-05-22 Ron Guerin <ron-at-vnetworx.net> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  17. 2011-05-22 Ron Guerin <ron-at-vnetworx.net> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  18. 2011-05-23 swd <sderrick-at-optonline.net> Subject: [NYLXS - HANGOUT] Membership Dues Address?
  19. 2011-05-23 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] Membership Dues Address?
  20. 2011-05-23 swd <sderrick-at-optonline.net> RE: [NYLXS - HANGOUT] Membership Dues Address?
  21. 2011-05-23 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Template Argument type deterination
  22. 2011-05-23 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] Membership Dues Address?
  23. 2011-05-23 swd <sderrick-at-optonline.net> RE: [NYLXS - HANGOUT] Membership Dues Address?
  24. 2011-05-23 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] Membership Dues Address?
  25. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [ian.bruntlett-at-gmail.com: [accu-general] Free e-book:- The
  26. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Job Fair
  27. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [billy.donahue-at-gmail.com: Re: [mrbrklyn-at-panix.com: Template
  28. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [ruben-at-mrbrklyn.com: Re: [mrbrklyn-at-panix.com: Template Argument
  29. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [ruben-at-mrbrklyn.com: Re: [mrbrklyn-at-panix.com: Template Argument
  30. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] [ruben-at-mrbrklyn.com: Re:
  31. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] [ruben-at-mrbrklyn.com: Re:
  32. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] [ruben-at-mrbrklyn.com: Re:
  33. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] template implicit converstion
  34. 2011-05-24 Ron Guerin <ron-at-vnetworx.net> Subject: [NYLXS - HANGOUT] NYLUG Workshop / Hacking Society (Smalltalk, C++, Python) Tuesday May 24 6:00PM-8:00PM
  35. 2011-05-24 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] [mrbrklyn-at-panix.com: (fwd) Template argument determination]
  36. 2011-05-25 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  37. 2011-05-25 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] C++ Workshop - New Webservices with OKWS -
  38. 2011-05-26 Ron Guerin <ron-at-vnetworx.net> Subject: [NYLXS - HANGOUT] NYLUG Presents: 6/15 -at- 6:30PM Robert Menes on Rockbox: Open Source Jukebox Firmware
  39. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Subject: [ruben-at-mrbrklyn.com: Re: [NYLXS - HANGOUT] C++ Workshop - New
  40. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Subject: [ruben-at-mrbrklyn.com: Re: [NYLXS - HANGOUT] C++ Workshop - New
  41. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Subject: [ruben-at-mrbrklyn.com: Re: [NYLXS - HANGOUT] C++ Workshop - New
  42. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Perl Class
  43. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Re: [NYLXS - HANGOUT] Perl Class
  44. 2011-05-26 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Postgres Class
  45. 2011-05-26 Paul Robert Marino <prmarino1-at-gmail.com> Re: [NYLXS - HANGOUT] Postgres Class
  46. 2011-05-27 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] C++ Workshop - next phase
  47. 2011-05-27 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Fwd: Consensus from last night's meeting
  48. 2011-05-27 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Fwd: Re: [The-New-York-Perl-Meetup-Group] Consensus from last night's
  49. 2011-05-30 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] Job opennings
  50. 2011-05-31 Ruben Safir <mrbrklyn-at-panix.com> Subject: [NYLXS - HANGOUT] C++ Workshop

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