Log 071917

I took a break after running into a few snags. For one, the Ocaml input/output (IO) specification wasn't very good. It neatly describes channels and cleanly separates them into input and output; that looks nice at first glance but what if you want both? I.e., a naive database application usually consists of seek operations followed by reads and writes. It's an odd design decision.

Then there is C++'s manner of working with stdin, stdout and stderr as well as istreams, ostreams and fstreams. They made the standard IO streams uncopyable! Implying you can only pass references but never copy them. Of course, you might be tempted to pass pointers but you run into another whole set of problems. For one, expect lots of template type errors, and also, you're not supposed to call delete when a standard stream goes out of scope.

Then there is the class inheritance design of C++'s streams. It's over-engineered to meet the requirements of an OO type system; here you also see that the type system forces a solution which is simply not that neat though multiple inheritance helps.

Looking at both specifications I can only conclude that C's POSIX file handles specification simply wasn't that bad.

I also started looking at libuv as the basis of file IO, and later multithreading. And I hit another snag: Callbacks don't neatly fit into a mostly referential transparant system. (Well, so far. Unless I come up with a scheme to make it fit.) The problem: Sure you can define a callback, sure it will read values from a pipe, but it can't do anything with it. It simply cannot inform another thread easily to continue evaluation with a calculated value. (Imagine multiple reading threads and one thread who consumes and writes the result back. It's difficult to combine results from multiple threads with one callback.)

I am tempted to roll out my own temporary solution for primitive IO. I am also tempted to ignore libuv and write a PAR combinator using C++ primitives. But libuv is cross-platform, well-maintained, scalable, and popular...