A+, then K, Q/kdb are closed source. I wonder in dollars, not users, how much of the market for paid compilers/systems they have at the price per seat they fetch. The fintech community pays dearly for them because they are effective.
I use J, which is not that popular. It was closed, but has been open source for a while now.
I use J, which is not that popular. It was closed, but has been open source for a while now.