IParse VS cant

Nice library with many features. But I do not always understand the focus on memory usage. I guess that the reason behind this is that less memory allocations, have a positive effect on execution times. In a parser, where you often have to compare identifiers, it is a good idea to put all strings for identifiers into a unique pointer with the help of a hash table.

In my interpreting parser [1] I use a hexa hash tree [2] for storing identifiers. It is not very memory efficient, but very fast. It turns every string (from the input buffer) into a unique pointer for that string pointing to a copy of the string. In this way comparing string (identifiers) is equivalent to comparing pointers.

The idea of the hexa hash tree is that is a tree where each node has sixteen child nodes. Which node is selected is based on a step wise evaluated hash function that first takes the lower four bytes of the string, and after reaching the end of the string, the higher four bytes of the string. The nodes often taken up more memory space than the strings themselves.

[1] https://github.com/FransFaase/IParse/

[2] https://github.com/FransFaase/IParse/blob/master/software/Id...

I wrote a tool that can process a number of MarkDown files with fragments of C code and put all those fragments in the right order to produce a file that can be compiled. It is grammar based and works with manipulating Abstract Syntax Trees, so I guess, it could be adapted for different programming languages. See: https://github.com/FransFaase/IParse#markdownc

Interesting. I have not looked into the code, but I wonder whether it is a compiler, or just an interpreter, e.g. it converts the grammar into some internal representation that is executed by an interpreter or virtual machine. I started worked on an interpreting parser in C many years ago. And later also made Java, C++ and JavaScript version of it. For the JavaScript implementation, see: https://fransfaase.github.io/ParserWorkshop/Online_inter_par... For the C++ version, see: https://github.com/FransFaase/IParse

I implemented an unparse function in IParse, which is not a parser generator, but a parser that interprets a grammar. See for example https://github.com/FransFaase/IParse/blob/master/software/c_... where symbols starting with a back slash are a kind of white space terminals during the unparse. For example, \inc stands for incrementing the indentation where \dec decrements it. The \s is used to indicate that at given location a space should be included.

That was one of the short examples in Norvig's Python program-design course for Udacity. https://github.com/darius/cant/blob/master/library/regex-gen... (I don't have the Python handy.)

> figure out a way to do upward movement that doesn’t require annoying special casing. If you figure it out, don’t tell me since it means I’ll have to make more levels.

Don't read this, then: https://github.com/darius/cant/blob/master/examples/games/20...

As long as I'm commenting, here are some links to other console Sokobans I thought were fun (listed in the source code to mine). The sed one is nuts -- I had no idea it could do that: https://github.com/darius/cant/blob/master/examples/games/20...

I've done AoC using my own language before. As a task it's at a sweet spot for finding weaknesses in the language/library/implementation: real and varied enough to exercise your system, small chunks of work, lots of code to compare yours to, with fun and competitive juices.

The first time I did it it forced me to fix some major problems. My language would still be a handicap for me in the state it's in (though I did get on the leaderboard a couple times using it).

fwiw: https://github.com/darius/cant (haven't done this year's so far)

I've used my own hobby language Cant before, for a couple reasons: it's meant to be enjoyable to code in (at least for me), and tackling random problems like this is a good way to drive some improvements to it.

Also similar: the 'for' expression in Cant (search for "syntax: for").

Darius Bacon wrote a version of this in https://github.com/darius/cant/blob/master/library/factoring... where the "frontier" of active riders is stored in a hash table rather than a bin heap, which is almost certainly a more efficient approach. But he's not doing the bitmaps.

Thank you!

I dislike style nazis too, e.g. carping when Peter Norvig's code won't pass PEP 8.

I'm just leery of the expected cost in this kind of case. It can go on working for years until some new complication or some change in the ecosystem makes it suddenly create a really weird problem. Or when you want to try moving to a fancy new Python implementation, you find you have this friction. Matter of judgement where some chance of such messes is paid for by what it can do for you. (Of course when it's less "load bearing" the balance shifts.) With https://coverage.readthedocs.io/en/stable/ for example, it used bytecode hacks to do something you couldn't do otherwise, and that's unlikely to mess you up.

I have had old C programs go crazy years later in a really hard to debug way because newer compilers may interpret your code like your ex-wife's divorce lawyer (as Kragen put it, iirc). Back in the day a lot of us thought we had a different kind of relationship with C compilers, and it'd be fine to code to that informal social contract. (Just a loose analogy.)

I'm piddling away at https://github.com/darius/cant these days. (Some of the motivation was feeling too confined by Python, actually.) No Wasm, but I'm happy it exists! I tried to make a system like it 20 years ago (Idel) and gave up too soon.

Agreed. I used a few Rosetta Code problems in https://github.com/darius/cant/tree/master/examples and https://github.com/darius/cant/tree/master/library, but Rosetta is mostly things I don't care about.

Just for fun I tried it on my own toy language that nobody but me uses -- going to the limit in nicheness. E.g. Project Oiler problem #1 -- it's very wrong, but no shame in that.