brew install gsl not working

[jess-churchill]

Hi there, I'm trying to install gsl on my Apple Silicon M1 using brew and the documentation says to type "brew install gsl". When I do this, it says:
Warning: gsl 2.7.1 is already installed and up-to-date. To reinstall 2.7.1, run: brew reinstall gsl
and appears to be installed successfully, however, when I then try to compile c++ code using g++ -Wall -o test.out test.cpp -lgslcblas is says:
fatal error: gsl/gsl_math.h: No such file or directory 13 | #include <gsl/gsl_math.h> | compilation terminated.

Any suggestions as to how to link gsl to the c++ compiler?

[jess-churchill]

Solution from @rouzbehy:
g++ -Wall -I/opt/homebrew/Cellar/gsl/2.7.1/include -c test.cpp -o test.o
g++ -L/opt/homebrew/Cellar/gsl/2.7.1/lib test.o -lgsl -lgslcblas -o test.out

[carlocab]

Try passing -I/opt/homebrew/include and -L/opt/homebrew/lib to the compiler.

[carlocab]

Solution from @rouzbehy:

g++ -Wall -I/opt/homebrew/Cellar/gsl/2.7.1/include -c test.cpp -o test.o

g++ -L/opt/homebrew/Cellar/gsl/2.7.1/lib test.o -lgsl -lgslcblas -o test.out

You should avoid referring to Cellar paths. Those are unstable and could change at any time. Instead, use

g++ -Wall -I/opt/homebrew/opt/gsl/include -c test.cpp -o test.o 

or

g++ -L/opt/homebrew/opt/gsl/lib test.o -lgsl -lgslcblas -o test.out

Alternatively, these should work too as long as you've never done brew unlink gsl:

g++ -Wall -I/opt/homebrew/include -c test.cpp -o test.o 

g++ -L/opt/homebrew/lib test.o -lgsl -lgslcblas -o test.out

[jess-churchill]

Okay great, thanks!