Language guide

[indexzero]

First Fascinating stuff. I really like your creativity here. I got turned onto computers through logo when I was 6 so teaching languages always have a special place in my heart.

Have you begun to formalize the language guide yet? It's usually one of the first things to do in these situations before going off an implementing all the language features.

Based on reading the code base and some example code:

  literals
  --------
  `my` is a reserved keyword representing the POV of the story
  `name` is a reserved keyword representing the name of the POV
  `room` is a reserved keyword representing a place the POV can move through 
  `summary` is a reserved keyword describing an entity in the story
  `exit` is a reserved keyword connecting rooms
  The language supports single quoted strings for attaching text to entities

  operators
  ---------
  `is` is equivalent to `=`. `is` may optionally be followed by `a` 
  but no grammar checking is done to determine if that is appropriate.
  `look` is an operator of examining entities
  `at` is a qualifying operator for look

That's all I got right now. Have you considered a Javascript version of the parser? It would make playing this in the browser much easier.

[maryrosecook]

Thanks very much for the pointer about a language guide, and for making a start. I've put this on my todo list.

The language is actually smaller than it appears. The stuff you see in the Isla code examples is a mix of core language features (only assignment and instantiation, at the moment), built in types (like list), and the storytelling environment that includes its own special types (like room). Further, there is the story-playing environment that has the rudimentary set of commands like look and go.

Some specifics:

Tokens like my, name, exit and summary are actually simply attribute identifiers on objects.

room is an object type. When an object type is coupled with an identifier in an expression like palace is a room, this instantiates an object of type room and assigns it to palace.

is is a keyword. It is, indeed, equivalent to = in other programming languages.

Thanks again for your suggestion and starting document. It's really nice that you are interested.

[indexzero]

@maryrosecook Great.

To my other point: I'd be happy to help with a lexer / parser implementation in Javascript. I really think there could be some very engaging ways to teach programming in the browser without having to make calls to a clojure backend all the time.

Not having a formal language guide is of course the big blocker for that because I don't want to stray from your vision for the language :)

[maryrosecook]

That would be so great! I think you are totally right: a client side implementation would really help with teaching.

I am going to continue work on the language guide right this second. I will try and have something for you by tomorrow night.

[nicholasbs]

Would it make sense to write the other lexer/parser in ClojureScript, rather than pure JavaScript? I know even less ClojureScript than I do Clojure, but I wonder if that might allow for some degree of code reuse?

Of course, now that I think about it, ClojureScript isn't self-hosting (yet), so you wouldn't eliminate the need for the JVM, which might defeat the purpose.

[maryrosecook]

Yes, it would allow quite a lot of code reuse. And it would be possible to produce a client-side-only environment, which would be great for deployment. But, as you say, a JVM would still be required to work on the Isla language itself.

I chose to write the compiler in Clojure because I wanted to learn Clojure. I think JS is probably a better all-round implementation language. Isla is not that complicated, so its compiler doesn't need to be written in a heavy duty language. Speed of execution is almost irrelevant. And the language environment is suited to the web, because that is where it will have the greatest reach.

[indexzero]

Personally I agree with @maryrosecook

Isla is not that complicated, so its compiler doesn't need to
be written in a heavy duty language.

Given the limited number of keywords I think lexing and parsing would be pretty straight forward with pure JS. Newlines are significant which also simplifies things. Naturally I'm biased here, but I've written a lexer / parser for Gherkin in the past and it wasn't much trouble. Got through most of it in 2 days.

[maryrosecook]

I think if a JS compiler were written, it would be a net win. So, if you'd like to go for it, @indexzero , please do. I'd be excited to help out. I plan to continue implementing a compiler in Clojure just for my own education.

[maryrosecook]

@indexzero I have bashed out a language guide. Let me know if I've missed out any information you need.

I have only written a guide for the language itself. I have not, yet, written the documents that describe the story writing environment or the story playing environment. I'm can't really do these yet, because both are in a great amount of flux as I experiment with stuff. Let me know if this is a problem and I can start making some concrete decisions sooner rather than later.

https://github.com/maryrosecook/isla/blob/master/languageguide.md

[indexzero]

@maryrosecook Nice! I'll take a stab at the lexer this weekend. Should I fork? Or just create an isla.js repository? This is your call, isla.js makes sense only if the mainline will continue to be clojure

[maryrosecook]

I think fork. I think it would be cool to keep both compilers in the same repository, for now. Then, a canonical compiler can emerge.

I'm really excited to see what you come up with.

[indexzero]

@maryrosecook Pretty much done with the Javascript lexer.

1. Fully-parsed lexemes are here
2. From these fixtures

Next up is parsing. The sample syntax in hallway.is suggests that items is a reserved keyword that does not need assignment.

hallway is a room
hallway summary is 'It is dark. You hear a girl crying.'
hallway items add rose

I would have expected:

hallway items is list

to be required before the hallway items add rose. Is that expected or just a typo in the test fixture?

[maryrosecook]

Fantastic! This is so exciting. Thanks very much for getting involved with the project.

That's a good question about hallway items.

The way this works is that room is actually a type with four attributes: name (a string), summary (a string), items (a list) and exit (an object reference). When you write hallway is a room, you are instantiating an object of type room and assigning the object to hallway. Thus, the hallway attribute items is automatically instantiated as a list when hallway is instantiated.

(By the way, list is also a type, so if you want to instantiate a variable as a list, you would go mylist is a list, not mylist is list.)

Is that clear?