You could use the Eigen linear algebra template library for C++. It is pretty complete with regards to BLAS and LAPACK functions and the interfaces are much easier to use (in my opinion).
A word of warning: You might quickly run into problems with the __float128 datatype because fundamental operation like e.g. log are not implemented.
Emacs with lsp-mode (https://github.com/emacs-lsp/lsp-mode) and flycheck (https://www.flycheck.org) will be a good choice to target multiple languages simultaneously.
According to lsp-mode supported languages table: fortran, c++, python, R and Julia are already supported
EMACS or XEMACS, and numerous other versions can act as an editor and IDE for multiple languages by using the packages that are available.
A recommended package repository is MELPA, but there are others, there you will find 3,543 Packages including ones for:
Just about everything.
EMACS is free, open source and ...
Semantic Designs' (my company) Source Code Search Engine (SCSE) provides this capability.
SCSE is mainly used to search large source code bases in many files in multiple programming languages efficiently. It provides a query language that lets one pose an interactive query in terms of the target language(s), and typically finds all the query matches in 1-...