The best a language can do is to fill a niche and to be very good at that particular thing. You should always use the language that is most suited for your problem, whatever that is. But there are many languages that let you get away with being a terrible programmer. Haskell just isn't like that and I want to point out that you can learn a great deal from being forced to think in more abstract ways, just like you did.
In programming, we often encounter the temptation to just mutate everything and to use side-effects since it's quite convenient to do so in the short-term. In the long-term, these things will come back and bite us. I argue that it is important that a programmer should have experienced what it is like to simply not have the option to do so. After learning Haskell, I tried to avoid side-effects in other languages as much as possible and to use them consciously. That was something I didn't even consider before learning Haskell. And, obviously, the less side-effects you have, the easier it is to maintain or exchange parts of your program.
I currently use Haskell to calculate probably a hundred analytical derivatives for a large sparse array that is used in a simulator written in Fortran. And it's very good at that. For quickly writing some evaluations of output of this simulator I use Python, because Python is better suited.
Pick a language based on the problem. Don't just use one language because you know it. In my experience, Haskell is very well suited for a lot of mathematical stuff.
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Off topic:
By the way, Einstein's field equations will work for gravity in the classical regime, not in all cases. But still, if you simply want to calculate how far you'll throw a ball, you really should take another model based on Newtonian gravity or simply take a constant gravitational force. Planetary movements are also fine with Newtonian gravity (except when you really need it accurately. E.g. for the precession of the perihelion of mercury). However, GPS calculations are terribly inaccurate without general relativity (time flows differently if you are close to a big gravitational potential well). So, pick your model based on what you want to do, just like you pick your programming language based on what you want to do.
