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haku continued

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liquidex 2024-07-26 23:21:29 +02:00
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content/programming/blog/haku.tree
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@ -1133,6 +1133,9 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
```javascript
function arithmeticBuiltin(op) {
return (state, node) => {
if (node.children.length < 3)
throw new Error("arithmetic operations require at least two arguments");
let result = treewalk.eval(state, node.children[1]);
for (let i = 2; i < node.children.length; ++i) {
result = op(result, treewalk.eval(state, node.children[i]));
@ -1178,22 +1181,16 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
{:program=haku}
```javascript
import { getKernel } from "treehouse/components/literate-programming/eval.js";
import { getKernel, defaultEvalModule } from "treehouse/components/literate-programming/eval.js";
let kernel = getKernel();
export const kernel = getKernel();
export const defaultKernelInit = kernel.init;
kernel.init = () => {
return defaultKernelInit();
};
export const defaultKernelEvalModule = kernel.evalModule;
kernel.evalModule = async (state, source, language, params) => {
if (language == "haku") {
printEvalResult(source);
return true;
} else {
return await defaultKernelEvalModule(state, source, language, params);
return await defaultEvalModule(state, source, language, params);
}
};
```
@ -1542,6 +1539,705 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
3
```
% id = "01J42RD8Y4VYAQB97XY057R26G"
- being able to define arbitrary functions gives us some pretty neat powers!
to test this out, let's write a little program that will calculate Fibonacci numbers.
% id = "01J42RD8Y4FJXH7HGG2AT3SDJC"
- there are a couple ways to write a number to calculate numbers in the Fibonacci sequence.
% id = "01J42RD8Y4SWPXCT67J8XKX87Z"
- the most basic is the recursive way, which is really quite simple to do:
{:program=fib-recursive}
```javascript
function fib(n) {
if (n < 2) {
return n;
} else {
return fib(n - 1) + fib(n - 2);
}
}
console.log(fib(10));
```
{:program=fib-recursive}
```output
55
```
the downside is that it's really inefficient! we end up wasting a lot of time doing repeat calculations.
try going through it yourself and see just how many calculations are repeated!
% id = "01J42RD8Y4V3G6RCB2ZABSTE5R"
- the one that's more efficient is the iterative version:
{:program=fib-iterative}
```javascript
function fib(n) {
let a = 0;
let b = 1;
let t = null;
for (let i = 0; i < n; ++i) {
t = a;
a = b;
b += t;
}
return a;
}
console.log(fib(10));
```
{:program=fib-iterative}
```output
55
```
% id = "01J42RD8Y4T30Z1BP0MZXHG4C8"
- in either, you will notice we need to support comparisons to know when to stop iterating!
so let's add those into our builtins:
{:program=haku}
```javascript
function comparisonBuiltin(op) {
return (state, node) => {
if (node.children.length != 3)
throw new Error("comparison operators require exactly two arguments");
let a = treewalk.eval(state, node.children[1]);
let b = treewalk.eval(state, node.children[2]);
return op(a, b) ? 1 : 0;
};
}
builtins["="] = comparisonBuiltin((a, b) => a === b);
builtins["<"] = comparisonBuiltin((a, b) => a < b);
```
it's easy enough to `!=`, `<=`, `>`, and `>=` from these, so we won't bother adding those in for now.
% id = "01J42RD8Y4H02HKWVD650T9BYG"
- if you're curious how to derive `!=` and `<=`, consider that we're returning zeros and ones, so we can do an AND operation by multiplying them.
% id = "01J42RD8Y4WZSKMT0BYXBM91GE"
- `>` can be derived by reversing the arguments of `<`.
% id = "01J42RD8Y4EWZ0V4KC7HX2KJAZ"
- of course, we'll also need an `if` to be able to branch on the result of our comparison operators.
{:program=haku}
```javascript
builtins["if"] = (state, node) => {
if (node.children.length != 4)
throw new Error("an `if` must have a condition, true expression, and false expression");
let condition = treewalk.eval(state, node.children[1]);
if (condition !== 0) {
return treewalk.eval(state, node.children[2]);
} else {
return treewalk.eval(state, node.children[3]);
}
};
```
% id = "01J42RD8Y4XBB8WE9QR36WFAQH"
- now we can write ourselves a recursive Fibonacci!
{:program=haku}
```haku
((fn (fib)
(fib fib 10))
; fib
(fn (fib n)
(if (< n 2)
n
(+ (fib fib (- n 1)) (fib fib (- n 2))))))
```
note that in order to achieve recursion, we need to pass `fib` into itself - this is because the `fib` variable we're binding into the first function is not visible in the second function.
but if we run it now:
{:program=haku}
```output
55
```
we can see it works just as fine as the JavaScript version!
% id = "01J42RD8Y4BS3EBAQXNR410ZH5"
- ### [rememeber to remember](https://www.youtube.com/watch?v=0ucW1eN8h9Y){.secret}
% id = "01J42RD8Y47WMW5DSVFVCADF60"
- now, you might be wondering why I'm cutting our Fibonacci adventures short.
after all, we're only just getting started?
% id = "01J42RD8Y46NJ03J6ZMT2EDBDB"
- thing is, I _really_ want to build something bigger.
and one expression per code block's not gonna cut it.
% id = "01J42RD8Y4SJS75FTA9SQ28RE2"
- I'd like to start building a little library of utilities for writing haku code, but I have no way of saving these utilities for later!
% id = "01J42RD8Y4GA0Q5Q2Z446DRD5Y"
- therefore, it's time for... a persistent environment!
% id = "01J42RD8Y4DCWSG17XJFSJF1SR"
- once again, let me sketch out what I'd like it to look like.
to declare a persistent value, you use `def`:
```haku
(def fib
(fn (n)
(if (< n 2)
n
(+ (fib (- n 1)) (fib (- n 2))))))
```
if this looks familar, that's because it probably is - [I used the exact same example at the start of the post][branch:01J3K8A0D1198QXV2GFWF7JCV0]!
% id = "01J42RD8Y46GDWJA41A76B57VF"
- once you `def`ine a persistent value, you can refer to it as usual.
persistent values will sit in a scope _above_ builtins, so you will be able to shadow those if you want to (but please don't.)
```haku
(def fn if) ; Whoops! Guess your soul belongs to me now
```
% id = "01J42RD8Y4ZF0XQH1RT020099B"
- of course, values will persist across code blocks, so I'd be able to refer to `fib` here as well:
```haku
(fib 12)
```
% id = "01J42RD8Y4EDKYXXZZ5SGFQCCS"
- and lastly, it'll be possible to put multiple expressions in a code block.
we'll only treat the last one as the result.
```haku
(def x 1)
(def y 2)
(def z (+ x y))
```
% id = "01J42RD8Y4FJ1S12WG27DVWFD7"
- so let's start by implementing the easiest part - the `def` builtin.
we'll need to augment our interpreter state once again, this time with the persistent environment:
{:program=haku}
```javascript
treewalk.init = (env, input) => {
return {
input,
scopes: [new Map(Object.entries(builtins)), env],
env,
};
};
```
% id = "01J42RD8Y4BWY2B56NMSNR27EP"
- of course now we will also need to teach our whole runtime about the environment, right down to the kernel...
{:program=haku}
```javascript
import { defaultEvalModule } from "treehouse/components/literate-programming/eval.js";
export function run(env, input, node) {
let state = treewalk.init(env, input);
return treewalk.eval(state, node);
}
export function printEvalResult(env, input) {
try {
let tokens = lex(input);
let ast = parse(tokens);
let result = run(env, input, ast);
// NOTE: `def` will not return any value, so we'll skip printing it out.
if (result !== undefined) {
console.log(result);
}
} catch (error) {
console.log(error.toString());
}
}
kernel.evalModule = async (state, source, language, params) => {
if (language == "haku") {
state.haku ??= { env: new Map() };
printEvalResult(state.haku.env, source);
return true;
} else {
return await defaultEvalModule(state, source, language, params);
}
};
```
% id = "01J42RD8Y4BREBB4KQ2WR0TH8Q"
- now for `def` - it'll take the value on the right and insert it into `env`, so that it can be seen in the future.
{:program=haku}
```javascript
builtins.def = (state, node) => {
if (node.children.length != 3)
throw new Error(
"a `def` expects the name of the variable to assign, and the value to assign to the variable",
);
if (node.children[1].kind != "identifier")
throw new Error("variable name must be an identifier");
let name = node.children[1];
let value = treewalk.eval(state, node.children[2]);
state.env.set(state.input.substring(name.start, name.end), value);
};
```
% id = "01J42RD8Y4FZNB2FV99YH00EHZ"
- now let's test it out!
{:program=haku}
```haku
(def x 1)
```
{:program=haku}
```haku
(+ x 1)
```
{:program=haku}
```output
2
```
seems to be working!
% id = "01J42RD8Y4HST3XK86HBVFA2XT"
- now for the second part: we still want to permit multiple declarations per block of code, but currently our syntax doesn't handle that:
{:program=haku}
```haku
(def x 1)
(def y 2)
```
{:program=haku}
```output
Error: unhandled node kind: error
```
~and by the way, I know this is a terrible error message. we'll return to that later.~
% id = "01J42RD8Y4JA8AZ7WT8E0WMXNA"
- this is a pretty simple augmentation to the base syntax.
instead of reading a single expression, we will read a _toplevel_ - as many expressions as possible until we hit `end of file`.
{:program=haku}
```javascript
parser.parseToplevel = (state) => {
let children = [];
while (parser.current(state).kind != eof) {
children.push(parser.parseExpr(state));
}
return {
kind: "toplevel",
children,
// Don't bother with start..end for now.
};
};
parser.parseRoot = (state) => parser.parseToplevel(state);
```
% id = "01J42RD8Y40SQVBHRBRWHWM9WD"
- I'm stealing the name _toplevel_ from OCaml.
the name _file_ didn't quite seem right, since a haku program is not really made out of files, but is rather a long sequence of code blocks.
% id = "01J42RD8Y4BYF2S4YSB4QB7YAQ"
- with a `toplevel` node ready, we can now handle it in our interpreter:
{:program=haku}
```javascript
treewalk.eval = (state, node) => {
switch (node.kind) {
case "integer":
let sourceString = state.input.substring(node.start, node.end);
return parseInt(sourceString);
case "identifier":
return treewalk.lookupVariable(state, state.input.substring(node.start, node.end));
case "list": {
let functionToCall = treewalk.eval(state, node.children[0]);
let result = functionToCall(state, node);
return result;
}
case "toplevel":
let result = undefined;
for (let i = 0; i < node.children.length; ++i) {
result = treewalk.eval(state, node.children[i]);
if (result !== undefined && i != node.children.length - 1)
throw new Error(`expression ${i + 1} had a result despite not being the last`);
}
return result;
default:
throw new Error(`unhandled node kind: ${node.kind}`);
}
};
```
% id = "01J42RD8Y49ZB65BE7C6WQRDZT"
- since `eval` (and likewise, a treehouse code block) is only allowed to have one result, we disallow any results other than the first one.
% id = "01J42RD8Y4A18TXC73V2020ZWH"
- and with that...
{:program=haku}
```haku
(def x 1)
(def y 2)
(+ x y)
```
{:program=haku}
```output
3
```
we can now declare multiple, persistent values per code block!
% id = "01J42RD8Y4QDRRGT2JRPYKR7GE"
- ### but it's never that easy is it
% id = "01J42RD8Y4XTD4N5S2KWQQC6DX"
- so let's declare a little function to add some numbers together...
{:program=haku}
```haku
(def add-two
(fn (x) (+ x 2)))
```
{:program=haku}
```haku
(add-two 1)
```
{:program=haku}
```output
Error: variable is undefined
```
'scuse me??
% id = "01J42RD8Y473B94NGG17REKXH0"
- not gonna lie, this one took me a while to figure out!
but recall the structure of our AST nodes.
it looks something like this:
```json
{
"kind": "identifier",
"start": 30,
"end": 32
}
```
% id = "01J42RD8Y44MHWB6HTDKKBYPA2"
- now remember what we do in order to look up variables.
```javascript
return treewalk.lookupVariable(state, state.input.substring(node.start, node.end));
```
what do you imagine happens when the `state.input` source string is different?
% id = "01J42RD8Y4FQZW5PBTZYQCAHG4"
- _and_, the source string _does_ end up being different, because we end up parsing each block from scratch - we never concatenate them into something bigger!
% id = "01J42RD8Y4KJCNNKNS74AQ7BEH"
- so we'll have to fix this up by remembering the source string alongside each node somehow.
I see two paths:
% id = "01J42RD8Y4PVBEYMHN43ZNWW6Z"
- pre-slice the source string into each node
% id = "01J42RD8Y48GK9QWMCRGM71KDM"
- store a reference to the entire source string in each node
% id = "01J42RD8Y4BBB813M8GZ5MZTPP"
+ I'm no JavaScript optimization expert, but the 2nd option seems like it would avoid a bit of overhead...
but I really _do_ like the fact our AST can be neatly printed into readable JSON, so to preserve that property, we'll go with the 1st option.
% id = "01J42RD8Y48Y1S1R92ZPXGH9Q5"
- speed isn't really our main concern with this first iteration of the interpreter - I prefer inspectability and easy prototyping.
% id = "01J42RD8Y4Y0E5HATN35JKJ05G"
- we'll write a function that walks over our AST, and inserts source strings into it.
{:program=haku}
```javascript
export function insertSources(node, input) {
if (node.start != null) {
node.source = input.substring(node.start, node.end);
}
if (node.children != null) {
for (let child of node.children) {
insertSources(child, input);
}
}
}
```
% id = "01J42RD8Y4HMG0E6KZFTDRAZ4R"
- now I _am_ aware this is changing [object shapes][] quite a lot, which is suboptimal.
but I would _really_ like to keep the interpreter simple, so bear with me.
[object shapes]: https://mathiasbynens.be/notes/shapes-ics
% id = "01J42RD8Y4RXF274JDZRWAXZ6D"
- now we can patch the relevant parts of the interpreter to read from the `node.source` field, instead of `substring`ing the source string passed to the interpreter. this is pretty mechanical so I'll just dump all the relevant code here:
{:program=haku}
```javascript
treewalk.eval = (state, node) => {
switch (node.kind) {
case "integer":
return parseInt(node.source); // <--
case "identifier":
return treewalk.lookupVariable(state, node.source); // <--
case "list":
let functionToCall = treewalk.eval(state, node.children[0]);
return functionToCall(state, node);
case "toplevel":
let result = undefined;
for (let i = 0; i < node.children.length; ++i) {
result = treewalk.eval(state, node.children[i]);
if (result !== undefined && i != node.children.length - 1)
throw new Error(`expression ${i + 1} had a result despite not being the last`);
}
return result;
default:
throw new Error(`unhandled node kind: ${node.kind}`);
}
};
builtins.fn = (state, node) => {
if (node.children.length != 3)
throw new Error("an `fn` must have an argument list and a result expression");
let params = node.children[1];
if (node.children[1].kind != "list")
throw new Error("expected parameter list as second argument to `fn`");
let paramNames = [];
for (let param of params.children) {
if (param.kind != "identifier") {
throw new Error("`fn` parameters must be identifiers");
}
paramNames.push(param.source); // <--
}
let expr = node.children[2];
return makeFunction(state, paramNames, expr);
};
builtins.def = (state, node) => {
if (node.children.length != 3)
throw new Error(
"a `def` expects the name of the variable to assign, and the value to assign to the variable",
);
if (node.children[1].kind != "identifier")
throw new Error("variable name must be an identifier");
let name = node.children[1];
let value = treewalk.eval(state, node.children[2]);
state.env.set(name.source, value); // <--
};
```
% id = "01J42RD8Y4YWW1DR71RE5A1RC3"
- and of course, to top it all off, we still need to insert source information into the nodes before evaluating our tree:
{:program=haku}
```javascript
import { defaultEvalModule } from "treehouse/components/literate-programming/eval.js";
export function printEvalResult(env, input) {
try {
let tokens = lex(input);
let ast = parse(tokens);
insertSources(ast, input); // <--
let result = run(env, input, ast);
// NOTE: `def` will not return any value, so we'll skip printing it out.
if (result !== undefined) {
console.log(result);
}
} catch (error) {
console.log(error.stack ? error.toString() + "\n\n" + error.stack : error.toString());
}
}
kernel.evalModule = async (state, source, language, params) => {
if (language == "haku") {
state.haku ??= { env: new Map() };
printEvalResult(state.haku.env, source);
return true;
} else {
return await defaultEvalModule(state, source, language, params);
}
};
```
% id = "01J42RD8Y4QJS26B0EFSSZES3P"
- let's see if `add-two` works now.
we have an outdated version of it in our `env` map, so let's declare it again, using two input blocks like we did before:
{:program=haku}
```haku
(def add-two
(fn (x) (+ x 2)))
```
{:program=haku}
```haku
(add-two 2)
```
{:program=haku}
```output
4
```
cool!
% id = "01J42RD8Y4NKFM2KS4J5EQ7J2M"
- ### data structures
% id = "01J42RD8Y46XQ0A8SAYCXD5HMZ"
- for a language to really be useful, it needs to have data structures.
fortunately we already have them at our disposal - enter *linked lists!*
% id = "01J42RD8Y48GHZ145RM9Z6CAQW"
- the coolest part about lists is that we don't even need to do anything on the JavaScript side to implement them - we can use our good old friend Lambda calculus, along with a really cool tool called [Church encoding][], which allows us to encode lists using nothing but functions!
[Church encoding]: https://en.wikipedia.org/wiki/Church_encoding
% id = "01J42RD8Y424WKHG4C16ZXW3WC"
- haku also has some tricks up its sleeve which allows us to break free from the minimalistic confines of Lambda calculus, which means we don't have to implement _everything_.
without further ado though, let's get started!
% id = "01J42RD8Y49SN1TDA7ST663958"
- first, we'll implement a way to construct a linked list node - aka `cons`.
{:program=haku}
```haku
(def clist/cons
(fn (h t)
(fn (get)
(get h t))))
```
% id = "01J42RD8Y4YFBQPV75DNDG7S2F"
- the way our lists will work is that each list node is an ordinary function.
we'll be able to pass a "getter" function to the list function to obtain the list's head and tail.
% id = "01J42RD8Y4JK7R4K43A102DQXW"
- I'm prefixing all of our Church-encoded list operations with `clist/` to differentiate them from potential future list representations we'd want to implement.
% id = "01J42RD8Y4J7WPR0WTKMFSZWXJ"
- now for extracting our head and tail.
{:program=haku}
```haku
(def clist/head
(fn (list)
(list (fn (h t) h))))
(def clist/tail
(fn (list)
(list (fn (h t) t))))
```
these happen by passing that getter function to our list and using it to extract its head or tail _only._
% id = "01J42RD8Y4KNKKBVZNF4PCNPWB"
- the last missing part is a marker for signifying the end of the list.
thing is, we don't really have to implement this, because we already have the literal `0`! so knowing whether we're at the end of the list is as simple as `(= (clist/tail node) 0)`.
% id = "01J42RD8Y49H5NWQY1TJNRBWCT"
- and that's our list representation!
let's give it a shot.
we'll define a list containing a bunch of the first five Fibonacci numbers:
{:program=haku}
```haku
(def clist-with-fib-5
(clist/cons 1 (clist/cons 1 (clist/cons 2 (clist/cons 3 (clist/cons 5 0))))))
```
% id = "01J42RD8Y4X61HPNY7E5RZDC03"
- and a function to _reduce_ a list to a single element.
this function has various names in various languages, but the idea is that it allows us to walk over a list, modifying a value along the way, until we get a single, final value.
{:program=haku}
```haku
(def clist/reduce
(fn (init op list)
(if (= (clist/tail list) 0)
(op init (clist/head list))
(clist/reduce (op init (clist/head list)) op (clist/tail list)))))
```
once again, the recursive logic is kind of tricky; if you draw it out, you should be able to understand it much easier!
% id = "01J42RD8Y4HS91N3CG3BBYRD5D"
- let's see if we can sum our Fibonacci numbers together:
{:program=haku}
```haku
(clist/reduce 0 + clist-with-fib-5)
```
{:program=haku}
```output
12
```
nice!
% id = "01J42RD8Y4YVAV8M82229NT7E7"
- #### can I just say something real quick
% id = "01J42RD8Y49CBEG05CT288WJTN"
- I'm swiftly starting to dislike my parenthesized syntax choices here.
they would be fine in an editor capable of highlighting mismatched parentheses, but [Helix][] refuses to highlight _any_ parentheses in [`.tree`][branch:01H8V55APDWN8TV31K4SXBTTWB] files until I add a `tree-sitter` grammar to it.
[Helix]: https://helix-editor.com
% id = "01J42RD8Y4CKBD54RD089X1YKT"
- the example above took me way too long to get working than I want to admit.
honestly it's a failure of tooling on my side, (should've embedded source spans into all these errors so that they can be reported more cleanly!) but I _really_ don't want to spend too much time on what's basically just a prototype.
% id = "01J42RD8Y4ED5TTP392VYGGWXS"
- I'll carry on with them for a bit longer though, I really don't wanna write a complicated parser right now.
% stage = "Draft"
id = "01J3K8A0D1D0NTT3JYYFMRYVSC"
- ### tests
@ -1577,20 +2273,17 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
{:program=test-treewalk}
```javascript
import { lex, parse, exprToString } from "haku/sexp.js";
import { lex, parse, exprToString, insertSources } from "haku/sexp.js";
import { run } from "haku/treewalk.js";
let input = `
((fn (f)
((f 1) 2))
(fn (x)
(fn (y)
(+ x y))))
(def x 1)
`;
let tokens = lex(input);
let ast = parse(tokens);
console.log(run(input, ast));
insertSources(ast, input);
console.log(run(new Map(), input, ast));
```
{:program=test-treewalk}

38
static/js/components/haku/sexp.js
View file

@ -10,9 +10,7 @@ lexer.init = (input) => {
export const eof = "end of file";
lexer.current = (state) => {
return state.position < state.input.length
? state.input.charAt(state.position)
: eof;
return state.position < state.input.length ? state.input.charAt(state.position) : eof;
};
lexer.advance = (state) => ++state.position;
@ -31,10 +29,7 @@ lexer.skipWhitespaceAndComments = (state) => {
continue;
}
if (c == ";") {
while (
lexer.current(state) != "\n" &&
lexer.current(state) != eof
) {
while (lexer.current(state) != "\n" && lexer.current(state) != eof) {
lexer.advance(state);
}
lexer.advance(state); // skip over newline, too
@ -46,8 +41,7 @@ lexer.skipWhitespaceAndComments = (state) => {
};
export const isDigit = (c) => c >= "0" && c <= "9";
export const isIdentifier = (c) =>
/^[a-zA-Z0-9+~!@$%^&*=<>+?/.,:\\|-]$/.test(c);
export const isIdentifier = (c) => /^[a-zA-Z0-9+~!@$%^&*=<>+?/.,:\\|-]$/.test(c);
lexer.nextToken = (state) => {
let c = lexer.current(state);
@ -151,7 +145,19 @@ parser.parseList = (state, leftParen) => {
};
};
parser.parseRoot = parser.parseExpr;
parser.parseToplevel = (state) => {
let children = [];
while (parser.current(state).kind != eof) {
children.push(parser.parseExpr(state));
}
return {
kind: "toplevel",
children,
// Don't bother with start..end for now.
};
};
parser.parseRoot = (state) => parser.parseToplevel(state);
export function parse(input) {
let state = parser.init(input);
@ -184,3 +190,15 @@ export function exprToString(expr, input) {
return `<error ${expr.start}..${expr.end} '${inputSubstring}': ${expr.error}>`;
}
}
export function insertSources(node, input) {
if (node.start != null) {
node.source = input.substring(node.start, node.end);
}
if (node.children != null) {
for (let child of node.children) {
insertSources(child, input);
}
}
}

72
static/js/components/haku/treewalk.js
View file

@ -1,8 +1,12 @@
export const treewalk = {};
export const builtins = {};
treewalk.init = (input) => {
return { input, scopes: [new Map(Object.entries(builtins))] };
treewalk.init = (env, input) => {
return {
input,
scopes: [new Map(Object.entries(builtins)), env],
env,
};
};
treewalk.lookupVariable = (state, name) => {
@ -12,34 +16,46 @@ treewalk.lookupVariable = (state, name) => {
return scope.get(name);
}
}
console.log(new Error().stack);
throw new Error(`variable ${name} is undefined`);
};
treewalk.eval = (state, node) => {
switch (node.kind) {
case "integer":
let sourceString = state.input.substring(node.start, node.end);
return parseInt(sourceString);
return parseInt(node.source);
case "identifier":
return treewalk.lookupVariable(state, state.input.substring(node.start, node.end));
return treewalk.lookupVariable(state, node.source);
case "list":
let functionToCall = treewalk.eval(state, node.children[0]);
return functionToCall(state, node);
case "toplevel":
let result = undefined;
for (let i = 0; i < node.children.length; ++i) {
result = treewalk.eval(state, node.children[i]);
if (result !== undefined && i != node.children.length - 1)
throw new Error(`expression ${i + 1} had a result despite not being the last`);
}
return result;
default:
throw new Error(`unhandled node kind: ${node.kind}`);
}
};
export function run(input, node) {
let state = treewalk.init(input);
export function run(env, input, node) {
let state = treewalk.init(env, input);
return treewalk.eval(state, node);
}
function arithmeticBuiltin(op) {
return (state, node) => {
if (node.children.length < 3)
throw new Error("arithmetic operations require at least two arguments");
let result = treewalk.eval(state, node.children[1]);
for (let i = 2; i < node.children.length; ++i) {
result = op(result, treewalk.eval(state, node.children[i]));
@ -48,11 +64,25 @@ function arithmeticBuiltin(op) {
};
}
function comparisonBuiltin(op) {
return (state, node) => {
if (node.children.length != 3)
throw new Error("comparison operators require exactly two arguments");
let a = treewalk.eval(state, node.children[1]);
let b = treewalk.eval(state, node.children[2]);
return op(a, b) ? 1 : 0;
};
}
builtins["+"] = arithmeticBuiltin((a, b) => a + b);
builtins["-"] = arithmeticBuiltin((a, b) => a - b);
builtins["*"] = arithmeticBuiltin((a, b) => a * b);
builtins["/"] = arithmeticBuiltin((a, b) => a / b);
builtins["="] = comparisonBuiltin((a, b) => a === b);
builtins["<"] = comparisonBuiltin((a, b) => a < b);
export function makeFunction(state, paramNames, bodyExpr) {
let capturedScopes = [];
// Start from 1 to skip builtins, which are always present anyways.
@ -95,10 +125,36 @@ builtins.fn = (state, node) => {
if (param.kind != "identifier") {
throw new Error("`fn` parameters must be identifiers");
}
paramNames.push(state.input.substring(param.start, param.end));
paramNames.push(param.source);
}
let expr = node.children[2];
return makeFunction(state, paramNames, expr);
};
builtins["if"] = (state, node) => {
if (node.children.length != 4)
throw new Error("an `if` must have a condition, true expression, and false expression");
let condition = treewalk.eval(state, node.children[1]);
if (condition !== 0) {
return treewalk.eval(state, node.children[2]);
} else {
return treewalk.eval(state, node.children[3]);
}
};
builtins.def = (state, node) => {
if (node.children.length != 3)
throw new Error(
"a `def` expects the name of the variable to assign, and the value to assign to the variable",
);
if (node.children[1].kind != "identifier")
throw new Error("variable name must be an identifier");
let name = node.children[1];
let value = treewalk.eval(state, node.children[2]);
state.env.set(name.source, value);
};

43
static/js/components/literate-programming/eval.js
View file

@ -2,6 +2,13 @@ let outputIndex = 0;
export const jsConsole = console;
const loggingEnabled = false;
function log(...message) {
if (loggingEnabled) {
jsConsole.log("[eval]", ...message);
}
}
// Overwrite globalThis.console with domConsole to redirect output to the DOM console.
// To always output to the JavaScript console regardless, use jsConsole.
export const domConsole = {
@ -17,23 +24,21 @@ export const domConsole = {
},
};
let kernel = {
init() {
return {};
},
async evalModule(_state, source, language, _params) {
if (language == "javascript") {
let blobUrl = URL.createObjectURL(new Blob([source], { type: "text/javascript" }));
let module = await import(blobUrl);
for (let exportedKey in module) {
globalThis[exportedKey] = module[exportedKey];
}
return true;
} else {
return false;
export async function defaultEvalModule(_state, source, language, _params) {
if (language == "javascript") {
let blobUrl = URL.createObjectURL(new Blob([source], { type: "text/javascript" }));
let module = await import(blobUrl);
for (let exportedKey in module) {
globalThis[exportedKey] = module[exportedKey];
}
},
return _state;
} else {
return null;
}
}
let kernel = {
evalModule: defaultEvalModule,
};
export function getKernel() {
@ -52,11 +57,11 @@ export async function evaluate(commands, { error, newOutput }) {
signalEvaluationComplete = resolve;
});
let kernelState = kernel.init();
outputIndex = 0;
try {
let kernelState = {};
for (let command of commands) {
log(`frame ${treehouseSandboxInternals.outputIndex} module`, command);
if (command.kind == "module") {
await kernel.evalModule(
kernelState,
@ -71,10 +76,12 @@ export async function evaluate(commands, { error, newOutput }) {
++outputIndex;
}
}
log(`frame ${treehouseSandboxInternals.outputIndex} evalComplete`);
postMessage({
kind: "evalComplete",
});
} catch (err) {
log(`frame ${treehouseSandboxInternals.outputIndex} error`, err);
postMessage({
kind: "output",
output: {