C++ and Fortran interoperability -

for own entertainment have decided create large scale physics engine. have experience java , c++ none fortran. understanding of fortran is used in scientific industry , large calculations. decided use c++ gui, sound, user input, etc. might added while fortran handle calculations. how easy call fortran methods c++? have googled matter , haven't found information. despite not knowing fortran determined learn no matter how strict learning curve may (assuming appropriate performance increase). practical use fortran in way? decent performance increase (for large calculations)? fortran still used in modern world or outdated?

edit: there seams ongoing pattern of people downvoting without saying wrong question.

my understanding of fortran is used in scientific industry , large calculations.

fortran indeed used (still) in scientific , engineering applications, , in many other places well.

how easy call fortran methods c++?

the latest fortran standard has specific provisions interoperability c. facilities provide standard means c or c++ code call fortran routines, , fortran code call c routines , c++ routines having c linkage.

c , fortran routines have been calling each other longer c interop provisions have been in fortran standard, how accomplished without using interop features implementation dependent.

i determined learn [fortran] no matter how strict learning curve may (assuming appropriate performance increase).

although aspect's of fortran's structure make comparatively easy optimize number crunching, may disappointed if expect see large gains implementing numerical routines in fortran instead of c. performance more related algorithm choose language in implemented.

is practical use fortran in way?

yes.

will decent performance increase (for large calculations)?

it depends on lot of factors, rough estimate "no".

is fortran still used in modern world or outdated?

it still used, , fortran standard still maintained , periodically updated.