HPC administrator, researcher and scientific software developer here.
Inertia is not a bad thing, but a long living code evolves in strange ways, because of us, humans. First of all, programming languages and software design has a symbiotic relationship. They feed each other. Support for required patterns and new technology is added to languages, and designs are made in confines of language capabilities.
Moreover, technology changes with every generation. Hardware change, capabilities change, requirements change, designs and languages change. More importantly mindset change. So you're bolting modern designs over "vintage" designs. Inevitable shims get coded (sometimes implicitly), and thing get complicated, even with best documented designs and developers with well intentions. The code pushed down solidifies, knowledge fades, and documentation get lost unless it's bundled with the code repository.
As a result, legacy code becomes something of a monster, where developers don't want to see, touch, or work with.
My research was coded with C++11 in the beginning. If I want to modernize with C++14 or add new parts with C++14, these parts will probably look so different that it'll look like two different languages glued together with black magic. It's the same thing with long living FORTRAN code. Only with longer legacy.
The culture and dynamics around scientific and academic programming is different from both FOSS and commercial software. This needs to be taken into account.
Inertia is not a bad thing, but a long living code evolves in strange ways, because of us, humans. First of all, programming languages and software design has a symbiotic relationship. They feed each other. Support for required patterns and new technology is added to languages, and designs are made in confines of language capabilities.
Moreover, technology changes with every generation. Hardware change, capabilities change, requirements change, designs and languages change. More importantly mindset change. So you're bolting modern designs over "vintage" designs. Inevitable shims get coded (sometimes implicitly), and thing get complicated, even with best documented designs and developers with well intentions. The code pushed down solidifies, knowledge fades, and documentation get lost unless it's bundled with the code repository.
As a result, legacy code becomes something of a monster, where developers don't want to see, touch, or work with.
My research was coded with C++11 in the beginning. If I want to modernize with C++14 or add new parts with C++14, these parts will probably look so different that it'll look like two different languages glued together with black magic. It's the same thing with long living FORTRAN code. Only with longer legacy.
The culture and dynamics around scientific and academic programming is different from both FOSS and commercial software. This needs to be taken into account.