C++ libraries...!

[jo8et]

Hi all, I am just starting out using external libraries. I can compile and link the below code, for example. And I can produce and use library no problem

// mylib.h
#ifndef MYLIB_H
#define MYLIB_H
double calcSqrt(double);
#endif

// calc.cpp
#include <math.h>
#include "mylib.h"
double calcSqrt(double d)
{
        return sqrt(d);
}

// main.cpp
#include <stdio.h>
#include "mylib.h"
int main()
{
        double d = 100;
        printf("sqrt(%3.0f)=%2.0f\n",d,calcSqrt(d));
        return 0;
}

The only problem now is the next library I want to use (Aquila) has no equivalent of calc.cpp. ie I need to use the 1x master header file = master.h and my own main.cpp to build this library. I wonder does anyone have any tips? I tried to compile master.h to produce master.cpp but this cannot be right.

Sorry if this not well explained. Thank you

[George PlusPlus]

From the library's download page:

Aquila relies on CMake as a build tool, so make sure you have it installed (version 2.8 or later).

Do you have CMake installed? If so there are some instructions for the build.

[jo8et]

Thank you, will try this!

[jo8et]

Solved, thank you

[George PlusPlus]

Boost is another library you might want to look at, easier to install and deal with IMO.

Actually a lot of combined libraries. And a lot of newer C++ features started out being in Boost before being adopted into the C++ standard.

https://www.boost.org/

Boost builds itself, the instructions are easy to follow. Plus there are a lot of header-only Boost features.

If you want to get used to dealing with 3rd party libraries Boost is one of the best.

[jo8et]

Thank you! I was unaware of this huge library!

I am using mingw, so install is a bit more complex, but I found a github method which works
(search zrsmithson if anyone else needs it)

So now I have (many) header files:

C:\boost\include\boost-1_62\boost

And (many) Lib files:

C:\boost\lib

And an example.cpp

//#include <boost/regex.hpp>  //via boost example
#include "C:\boost\include\boost-1_62\boost\regex.hpp"    //my machine
#include <iostream>
#include <string>

int main()
{
    std::string line;
    boost::regex pat( "^Subject: (Re: |Aw: )*(.*)" );

    while (std::cin)
    {
        std::getline(std::cin, line);
        boost::smatch matches;
        if (boost::regex_match(line, matches, pat))
            std::cout << matches[2] << std::endl;
    }
}

So a standard C++ library format I guess.

Problem is I can't get this to compile! I know I need to supply the header files to compiler and the lib files to the linker, but am very confused as to how. I have this problem with other libraries too so it is my lack of knowledge...

eg I think it is something like this...

First of all convert example.cpp to object:
g++ -c example.cpp -o example.o


//other stuff here, not sure


Now link it:

g++ example.o -I. -L. -l -o example.exe

I am just not sure what flags to use. eg

-LC:\boost\lib

-IC:\boost\include\boost-1_62\boost

But I am not sure and pretty confused, especially coming from Python!

Any tips gratefully received

[TheIdeasMan]

So now I have (many) header files:

C:\boost\include\boost-1_62\boost

The latest version of boost is 1_77 :
https://www.boost.org/

I am guessing you literally followed the instructions on the page you found.

C++ already has regex, no need to use the boost one.

When compiling make sure to turn warnings on: they are your friend. It's worth reading the manual sometime there are other options not covered by -Wall -Wextra . And specify the standard.

g++ -std=c++20 -Wall -Wextra

as a minimum. The standard should ideally be the latest that your version of compiler will cope with. One can find out the version of g++ with :

g++ -v

[thmm]

C++ already has regex, no need to use the boost one.

According to the boost reference ans SO c++11 regex doesn't support lookbehinds so there is still a need for boost::regex.
https://theboostcpplibraries.com/boost.regex => see comment at bottom
https://stackoverflow.com/questions/14538687/using-regex-lookbehinds-in-c11