Re: [Dev-C++] Dev-cpp-users Digest, Vol 25, Issue 1

[Per W. <pw...@ia...>]

The question you should ask your self is: Are we helping you? If this is a
school assignment - which it looks to be - you can either use my code
(which would be a copyright violation and a violation of the terms your
school has), or you can look at my original post and then sit down and
spend some time on your own.

What code can _you_ produce? How would _you_ solve the problem? What would
_you_ learn if _you_ spend the time to wrangle a bit with your own code?

You can only improve as a developer - and turn in a solution to your
teacher with pride - if you spend real time programming. When you turn in
a job, you should not only be able to answer what a code line does. You
should also be able to answer why the line is there, and why it looks as
it does.

How much do you learn if you use a runtime-library function that someone
have told you to use? How much do you learn if you search through the
large set of available functions and select the ones to use yourself? How
many other functions will you learn about if you do not study the standard
functions available?

My suggestion: Do not continue with my code. Write a solution in C++
instead, by using streams. Then you will learn something new and you will
feel that you have done something. Just realize that a C++ implementation
is not a C implementation with function calls translated into "C++
functions". If you use streams, scan Google for a reasonable amount of
demo applications using streams and look how they do things. Don't
copy-paste individual code lines, but look how elegant streams-based C++
code should look and then design something similar but intended to solve
your specific problem. And for every variable or method code: Always think
what it does, and why you need it. And every time you call a function -
check in the manual if it may fail and why it may fail. What will _your_
code do to either make sure that it can not fail, or to give a correct
error message in case it fails?

Another thing: Spend time to figure out how you should test your code.
What is a reasonable "data file"? What are reasonable - and unreasonable -
search terms that you should test your code with. What happens if the text
matches?`What happens if the text doesn't match? Can you get buffer
overflows? Can you fail to open the data file? Does it matter if you
specify the word in capitals or mixed-case? Will it always produce a
result (or a failure) within a finite time? Will it always perform it's
job in a finite amount of memory? Does it matter if you run it on a 16-bit
or a 32-bit or a 64-bit processor? Does it matter if the processor stores
integers with least significant byte at lowest or highest memory address?
Does it matter if the compiler has signed or unsigned charactesr? What
happens if the data file is on a network, and the network cable is
unplugged in the middle of a scan? Are you making use of dynamic memory -
what happens if a memory allocation fails?

In short - no, you are not helped by getting turn-key implementations. The
only thing that helps you is you spending time doing exercices and you
thinking and you reading and you making mistakes and you detecting your
mistkaes and you correcting them.

/pwm

On Tue, 3 Jun 2008, Alexsandro Meireles wrote:

> Thank you all for helping me out.
>
> > From: dev...@li...> Subject: Dev-cpp-users Digest, Vol 25, Issue 1> To: dev...@li...> Date: Tue, 3 Jun 2008 01:33:27 -0700> > Send Dev-cpp-users mailing list submissions to> dev...@li...> > To subscribe or unsubscribe via the World Wide Web, visit> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users> or, via email, send a message with subject or body 'help' to> dev...@li...> > You can reach the person managing the list at> dev...@li...> > When replying, please edit your Subject line so it is more specific> than "Re: Contents of Dev-cpp-users digest..."> > > Today's Topics:> > 1. Re: templates + linker error (Per Westermark)> 2. Re: templates + linker error (Jorge Guevara)> 3. Re: templates + linker error (Per Westermark)> 4. Choose a word from a .txt file (Alexsandro Meireles)> 5. Re: Choose a word from a .txt file (Lloyd)> 6. Re: Choose a word from a .txt file (Per Westermark)> 7. Re: Choose a word from a .txt file (Per Westermark)> > > ----------------------------------------------------------------------> > Message: 1> Date: Mon, 26 May 2008 20:12:24 +0200 (CEST)> From: Per Westermark <pw...@ia...>> Subject: Re: [Dev-C++] templates + linker error> To: Lloyd <ll...@cd...>> Cc: dev...@li...> Message-ID:> <Pin...@ia...>> Content-Type: TEXT/PLAIN; charset=US-ASCII> > Think a bit about it.> > What code to you suggest that the compiler should enerate when it compiles> calc.cpp? If the compiler does not know that other source files will use> the template parameter "double", how will the compiler then be able to add> a "double" version of multiply when it compiles calc.cpp?> > Remember that it is the compiler, not the linker, that produces the> runnable code. The linker will have no use for an object file that doesn't> contain instantiated template functions.> > /pwm> > On Mon, 26 May 2008, Lloyd wrote:> > > The reason for the error is you are not passing the obj file of calc.cpp> > to the linker. Make appropriate settings in DevCpp. I think, you have to> > add calc.cpp to your project. Sorry I dont use DevCpp.> >> >> > On Sun, 2008-05-25 at 16:42 -0500, Jorge Guevara wrote:> > >> > > i have 3 source calc.h calc.cpp and principal.cpp (i compilated it> > > with devcpp)> > >> > > i have this error:> > > In function `main':> > > [Linker error] undefined reference to `calc<double>::multiply(double,> > > double)'> > > ld returned 1 exit status> > > [Build Error] ["Proyecto] Error 1> > >> > > somebody could help me please :)> > >> > > /********calc.h******/> > > #ifndef _CALC_H> > > #define _CALC_H> > >> > > template <class A_Type> class calc> > > {> > > public:> > > A_Type multiply(A_Type x, A_Type y);> > > A_Type add(A_Type x, A_Type y);> > >> > > };> > >> > > #endif> > >> > > /****calc.cpp******/> > > #include "calc.h"> > > #include <iostream>> > > using namespace std;> > >> > > template <class A_Type> A_Type calc<A_Type>::multiply(A_Type x,A_Type> > > y)> > > {> > > return x*y;> > > }> > > template <class A_Type> A_Type calc<A_Type>::add(A_Type x, A_Type y)> > > {> > > return x+y;> > > }> > >> > >> > > /******principal.cpp*****/> > > #include "calc.h"> > > #include <iostream>> > > #include <cstdlib>> > >> > > using namespace std;> > >> > > int main()> > > {> > > calc <double> a_calc_class;> > > double a, b;> > > a=4.3;> > > b=3.4;> > > a_calc_class.multiply(a,b);> > >> > > system("PAUSE");> > > return EXIT_SUCCESS;> > > }> > > /***************************/> > >> > >> > > -------------------------------------------------------------------------> > > This SF.net email is sponsored by: Microsoft> > > Defy all challenges. Microsoft(R) Visual Studio 2008.> > > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/> > > _______________________________________________ Dev-cpp-users mailing list Dev...@li... TO UNSUBSCRIBE: http://www23.brinkster.com/noicys/devcpp/ub.htm https://lists.sourceforge.net/lists/listinfo/dev-cpp-users> >> >> > ______________________________________> > Scanned and protected by Email scanner> >> > -------------------------------------------------------------------------> > This SF.net email is sponsored by: Microsoft> > Defy all challenges. Microsoft(R) Visual Studio 2008.> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/> > _______________________________________________> > Dev-cpp-users mailing list> > Dev...@li...> > TO UNSUBSCRIBE: http://www23.brinkster.com/noicys/devcpp/ub.htm> > https://lists.sourceforge.net/lists/listinfo/dev-cpp-users> >> > > > > ------------------------------> > Message: 2> Date: Tue, 27 May 2008 15:17:27 -0500> From: "Jorge Guevara" <jor...@gm...>> Subject: Re: [Dev-C++] templates + linker error> To: "Per Westermark" <pw...@ia...>> Cc: dev...@li...> Message-ID:> <51a...@ma...>> Content-Type: text/plain; charset="iso-8859-1"> > I try with this. and no problem> > #include <iostream>> #include <cstdlib>> #include "mypair.hpp"> #include "mypair.cpp" // i include the implementation in the source> principal.cpp> > the question is less efficient?, or its ok?> > bytes> > > 2008/5/26, Per Westermark <pw...@ia...>:> >> > The compiler can't create the code for a template function unless it sees> > the implementation when you try to use the template function.> >> > You should have the implementation of your multiply function in the header> > file, and not hidden in a cpp file.> >> > It is only the linker that will see the generated code from multiple cpp> > files, and neither the compiler nor the compiler knows that calc.cpp> > should create a specific version of the multiply function with the double> > data type.> >> > /pwm> >> >> > On Sun, 25 May 2008, Jorge Guevara wrote:> >> > > i have 3 source calc.h calc.cpp and principal.cpp (i compilated it with> > > devcpp)> > >> > > i have this error:> > > In function `main':> > > [Linker error] undefined reference to `calc<double>::multiply(double,> > > double)'> > > ld returned 1 exit status> > > [Build Error] ["Proyecto] Error 1> > >> > > somebody could help me please :)> > >> > > /********calc.h******/> > > #ifndef _CALC_H> > > #define _CALC_H> > >> > > template <class A_Type> class calc> > > {> > > public:> > > A_Type multiply(A_Type x, A_Type y);> > > A_Type add(A_Type x, A_Type y);> > >> > > };> > >> > > #endif> > >> > > /****calc.cpp******/> > > #include "calc.h"> > > #include <iostream>> > > using namespace std;> > >> > > template <class A_Type> A_Type calc<A_Type>::multiply(A_Type x,A_Type y)> > > {> > > return x*y;> > > }> > > template <class A_Type> A_Type calc<A_Type>::add(A_Type x, A_Type y)> > > {> > > return x+y;> > > }> > >> > >> > > /******principal.cpp*****/> > > #include "calc.h"> > > #include <iostream>> > > #include <cstdlib>> > >> > > using namespace std;> > >> > > int main()> > > {> > > calc <double> a_calc_class;> > > double a, b;> > > a=4.3;> > > b=3.4;> > > a_calc_class.multiply(a,b);> > >> > > system("PAUSE");> > > return EXIT_SUCCESS;> > > }> > > /***************************/> > >> >> >> > > -- > Ing. Jorge Luis Guevara Diaz> Bs Ciencias de la Computacion> Maestrante en Ciencia de la Computaci?n> http://jorge.sistemasyservidores.com http://inf.unitru.edu.pe/~jlgd> Escuela de Inform?tica - Universidad Nacional de Trujillo> Escuela de Ingenier?a de Sistemas - Universidad Privada del Norte> -------------- next part --------------> An HTML attachment was scrubbed...> > ------------------------------> > Message: 3> Date: Wed, 28 May 2008 06:36:29 +0200 (CEST)> From: Per Westermark <pw...@ia...>> Subject: Re: [Dev-C++] templates + linker error> To: Jorge Guevara <jor...@gm...>> Cc: dev...@li...> Message-ID:> <Pin...@ia...>> Content-Type: TEXT/PLAIN; charset=ISO-8859-1> > Always avoid including cpp files. cpp files are indented to generate> object files and be linked.> > Templated functions are intended to be compiled into object files first> when needed. As I wrote in one of my earlier mails, template functions> should be placed in the relevant header file.> > Look at the STL files: In all cases, the actual source code> for the implementations of lists, trees, arrays etc are available in the> header files.> > /pwm> > On Tue, 27 May 2008, Jorge Guevara wrote:> > > I try with this. and no problem> >> > #include <iostream>> > #include <cstdlib>> > #include "mypair.hpp"> > #include "mypair.cpp" // i include the implementation in the source> > principal.cpp> >> > the question is less efficient?, or its ok?> >> > bytes> >> >> > 2008/5/26, Per Westermark <pw...@ia...>:> > >> > > The compiler can't create the code for a template function unless it sees> > > the implementation when you try to use the template function.> > >> > > You should have the implementation of your multiply function in the header> > > file, and not hidden in a cpp file.> > >> > > It is only the linker that will see the generated code from multiple cpp> > > files, and neither the compiler nor the compiler knows that calc.cpp> > > should create a specific version of the multiply function with the double> > > data type.> > >> > > /pwm> > >> > >> > > On Sun, 25 May 2008, Jorge Guevara wrote:> > >> > > > i have 3 source calc.h calc.cpp and principal.cpp (i compilated it with> > > > devcpp)> > > >> > > > i have this error:> > > > In function `main':> > > > [Linker error] undefined reference to `calc<double>::multiply(double,> > > > double)'> > > > ld returned 1 exit status> > > > [Build Error] ["Proyecto] Error 1> > > >> > > > somebody could help me please :)> > > >> > > > /********calc.h******/> > > > #ifndef _CALC_H> > > > #define _CALC_H> > > >> > > > template <class A_Type> class calc> > > > {> > > > public:> > > > A_Type multiply(A_Type x, A_Type y);> > > > A_Type add(A_Type x, A_Type y);> > > >> > > > };> > > >> > > > #endif> > > >> > > > /****calc.cpp******/> > > > #include "calc.h"> > > > #include <iostream>> > > > using namespace std;> > > >> > > > template <class A_Type> A_Type calc<A_Type>::multiply(A_Type x,A_Type y)> > > > {> > > > return x*y;> > > > }> > > > template <class A_Type> A_Type calc<A_Type>::add(A_Type x, A_Type y)> > > > {> > > > return x+y;> > > > }> > > >> > > >> > > > /******principal.cpp*****/> > > > #include "calc.h"> > > > #include <iostream>> > > > #include <cstdlib>> > > >> > > > using namespace std;> > > >> > > > int main()> > > > {> > > > calc <double> a_calc_class;> > > > double a, b;> > > > a=4.3;> > > > b=3.4;> > > > a_calc_class.multiply(a,b);> > > >> > > > system("PAUSE");> > > > return EXIT_SUCCESS;> > > > }> > > > /***************************/> > > >> > >> > >> >> >> > --> > Ing. Jorge Luis Guevara Diaz> > Bs Ciencias de la Computacion> > Maestrante en Ciencia de la Computaci?n> > http://jorge.sistemasyservidores.com http://inf.unitru.edu.pe/~jlgd> > Escuela de Inform?tica - Universidad Nacional de Trujillo> > Escuela de Ingenier?a de Sistemas - Universidad Privada del Norte> >> > > > > ------------------------------> > Message: 4> Date: Tue, 3 Jun 2008 01:24:13 -0300> From: Alexsandro Meireles <ale...@ho...>> Subject: [Dev-C++] Choose a word from a .txt file> To: <dev...@li...>> Message-ID: <BAY...@ph...>> Content-Type: text/plain; charset="iso-8859-1"> > Dear users,> > How can I write a script to look a word in a .txt file with two columns (one is the word and the other is the answer I need) and give an answer which is in the second column. In other words, a user types a word, then the script match it with a word in a .txt file (first column) and gives the answer (second column).> > Thanks in advance!> > Alex.> _________________________________________________________________> Cansado de espa?o para s? 50 fotos? Conhe?a o Spaces, o site de relacionamentos com at? 6,000 fotos!> http://www.amigosdomessenger.com.br> -------------- next part --------------> An HTML attachment was scrubbed...> > ------------------------------> > Message: 5> Date: Tue, 03 Jun 2008 10:19:31 +0530> From: Lloyd <ll...@cd...>> Subject: Re: [Dev-C++] Choose a word from a .txt file> To: Alexsandro Meireles <ale...@ho...>> Cc: dev...@li...> Message-ID: <1212468571.3808.1.camel@RCCF025>> Content-Type: text/plain> > Wouldn't regular expression search help you? May be better solution> could be there...> > check for regex in www.boost.org> > > On Tue, 2008-06-03 at 01:24 -0300, Alexsandro Meireles wrote:> > Dear users,> > > > How can I write a script to look a word in a .txt file with two> > columns (one is the word and the other is the answer I need) and give> > an answer which is in the second column. In other words, a user types> > a word, then the script match it with a word in a .txt file (first> > column) and gives the answer (second column).> > > > Thanks in advance!> > > > Alex.> > > > > > ______________________________________> Scanned and protected by Email scanner> > > > ------------------------------> > Message: 6> Date: Tue, 3 Jun 2008 10:31:54 +0200 (CEST)> From: Per Westermark <pw...@ia...>> Subject: Re: [Dev-C++] Choose a word from a .txt file> To: Alexsandro Meireles <ale...@ho...>> Cc: dev...@li...> Message-ID:> <Pin...@ia...>> Content-Type: TEXT/PLAIN; charset=ISO-8859-1> > Why do you talk about scrit? This is the Dev-C++ list, where people> normally uses Dev-C++ to write C or C++ applications. The traditional use> of the word 'script' is for some interpretative programming - often in a> batch file or similar.> > Anyway - is the file sorted? Does it contain a huge number of words?> > If no to any of the above two questions: Open file. Read one line into a> buffer (for example with fgets()). Find the first separator character> (space, tab or whatever the file is using). Replace the separator with a> '\0'; Compare start of line with the word you want to match. If no match,> load next line and repeat. If match, step past the separator and then eath> any more separator characters. Locate the '\n' at end of the read line,> and replace with a '\0'; Emit the extracted answer.> > If the file is huge and sorted, get the file size. Move to the middle of> the file. Read one (possibly partial line). Read the next line. Extract> the word and see if you are above/below the requested language. If you> found the word - extract answer. If word too large, move back to one> quarter of the file and repat. If word was too small, seek to 75% of file> and repeat. All the time remember the <min,max> range that the> expected word must be in. Note that <min> and <max> should represent the> start position of text lines, (or the end-of-file) so when you> specify <min> as seek offset, you do not have to thow away any> potentially partial text lines - you know that it is a full line> and can check that word immediately.> > /pwm> > On Tue, 3 Jun 2008, Alexsandro Meireles wrote:> > > Dear users,> >> > How can I write a script to look a word in a .txt file with two columns (one is the word and the other is the answer I need) and give an answer which is in the second column. In other words, a user types a word, then the script match it with a word in a .txt file (first column) and gives the answer (second column).> >> > Thanks in advance!> >> > Alex.> > _________________________________________________________________> > Cansado de espa?o para s? 50 fotos? Conhe?a o Spaces, o site de relacionamentos com at? 6,000 fotos!> > http://www.amigosdomessenger.com.br> > > > > ------------------------------> > Message: 7> Date: Tue, 3 Jun 2008 10:33:12 +0200 (CEST)> From: Per Westermark <pw...@ia...>> Subject: Re: [Dev-C++] Choose a word from a .txt file> To: Lloyd <ll...@cd...>> Cc: Alexsandro Meireles <ale...@ho...>,> dev...@li...> Message-ID:> <Pin...@ia...>> Content-Type: TEXT/PLAIN; charset=US-ASCII> > No regular expressions if he is looking for an exact match. Regular> expressions are there to look for patterns. Normal strcmp()/strncmp() is> faster when looking for exact matches.> > /pwm> > On Tue, 3 Jun 2008, Lloyd wrote:> > > Wouldn't regular expression search help you? May be better solution> > could be there...> >> > check for regex in www.boost.org> >> >> > On Tue, 2008-06-03 at 01:24 -0300, Alexsandro Meireles wrote:> > > Dear users,> > >> > > How can I write a script to look a word in a .txt file with two> > > columns (one is the word and the other is the answer I need) and give> > > an answer which is in the second column. In other words, a user types> > > a word, then the script match it with a word in a .txt file (first> > > column) and gives the answer (second column).> > >> > > Thanks in advance!> > >> > > Alex.> > >> >> >> >> > ______________________________________> > Scanned and protected by Email scanner> >> > -------------------------------------------------------------------------> > This SF.net email is sponsored by: Microsoft> > Defy all challenges. Microsoft(R) Visual Studio 2008.> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/> > _______________________________________________> > Dev-cpp-users mailing list> > Dev...@li...> > TO UNSUBSCRIBE: http://www23.brinkster.com/noicys/devcpp/ub.htm> > https://lists.sourceforge.net/lists/listinfo/dev-cpp-users> >> > > > > ------------------------------> > -------------------------------------------------------------------------> This SF.net email is sponsored by: Microsoft> Defy all challenges. Microsoft(R) Visual Studio 2008.> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/> > ------------------------------> > _______________________________________________> Dev-cpp-users mailing list> Dev...@li...> TO UNSUBSCRIBE: http://www.noicys.cjb.net/devcpp/ub.htm> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users> > > End of Dev-cpp-users Digest, Vol 25, Issue 1> ********************************************
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