You're being feisty, whatever.
> We are discussing the overhead of forking processes to do math, which Python doesn't have to do.
Python uses dynamic dispatch on boxed types for every single operation. You're right this /only/ takes hundreds of instructions, but that just shows my analogy is appropriate. That's the turtle, in case you didn't understand it. I think it's silly for you to say this is "tolerably slow" for anyone but yourself. For other people, a fork per operation is completely tolerable. (I'm not one of those people...)
> [...] explain how a bash JIT compiler could optimize out all the instructions necessary to fork "bc" to call the cos instruction.
If anyone cared, bash could implement "bc" as a builtin the same way it does "echo". That'd be ugly, but it seems like the kind of thing the GNU folks would do if it was a common enough use case.