Working tree-walk executor

This commit is contained in:
Linus Lee 2020-09-24 05:30:15 -04:00
parent 81b5a5b0f1
commit c79c0e4fec

157
main.js
View File

@ -8,7 +8,7 @@ WE SAID
SHOCKING DEVELOPMENT 1
END OF STORY
LIES! WE SAID
SHOCKING DEVELOPMENT n MULTIPLY factorial OF n
SHOCKING DEVELOPMENT n MULTIPLY factorial OF n SUBTRACT 1
END OF STORY
END OF STORY
@ -19,6 +19,12 @@ YOU WON'T WANT TO MISS result
PLEASE LIKE AND SUBSCRIBE
`
const Runtime = {
print(s) {
console.log(s.toString());
}
}
/* tokenizer */
/**
@ -369,7 +375,7 @@ class Parser {
}
return nodes;
}
expectIdent() {
expectIdentString() {
const ident = this.tokens.next();
if (typeof ident === 'string' && !ident.startsWith('"')) {
return ident;
@ -404,10 +410,10 @@ class Parser {
if (this.tokens.peek(T.With)) {
this.tokens.next(); // with
// with args
const args = [this.expectIdent()];
const args = [this.expectIdentString()];
while (this.tokens.peek() === T.Comma) {
this.tokens.next(); // comma
args.push(this.expectIdent());
args.push(this.expectIdentString());
}
return {
type: N.FnDecl,
@ -430,7 +436,10 @@ class Parser {
exprs.push(this.expr());
}
this.tokens.expect(T.EndOfStory);
return exprs;
return {
type: N.ExprGroup,
exprs: exprs,
};
}
throw new Error(`Parsing error: expected ident, literal, or block, got ${
@ -457,7 +466,7 @@ class Parser {
}
} else if (next === T.ExpertsClaim) {
// assignment
const name = this.expectIdent();
const name = this.expectIdentString();
this.tokens.expect(T.ToBe);
const val = this.expr();
return {
@ -494,6 +503,7 @@ class Parser {
const right = this.atom();
return {
type: N.BinaryOp,
op,
left,
right,
}
@ -515,14 +525,143 @@ class Parser {
/* executor (tree walk) */
/**
* Abused (slightly) to easily return values upstack
*/
class ReturnError {
constructor(value) {
this.value = value;
}
unwrap() {
return this.value;
}
}
class Environment {
constructor(nodes) {
constructor() {
this.scopes = [{}]; // begin with global scope
}
run(nodes) {
let rv;
for (const node of nodes) {
rv = this.eval(node);
}
return rv;
}
eval(node) {
const scope = this.scopes[this.scopes.length - 1];
switch (node.type) {
case N.NumberLiteral: {
return node.val;
}
case N.StringLiteral: {
return node.val;
}
case N.FnDecl: {
scope[node.name] = node;
return node;
}
case N.FnCall: {
const fn = this.eval(node.fn);
const args = node.args.map(arg => this.eval(arg));
const calleeScope = {};
fn.args.forEach((argName, i) => {
calleeScope[argName] = args[i];
});
this.scopes.push(calleeScope);
let rv;
try {
this.eval(fn.body);
} catch (maybeReturnErr) {
if (maybeReturnErr instanceof ReturnError) {
rv = maybeReturnErr.unwrap();
} else {
// re-throw
throw maybeReturnErr;
}
}
this.scopes.pop();
return rv;
}
case N.Ident: {
let i = this.scopes.length - 1;
while (i >= 0) {
if (node.val in this.scopes[i]) {
return this.scopes[i][node.val];
}
i --;
}
console.log(this.scopes[this.scopes.length - 1]);
throw new Error(`Runtime error: Undefined variable "${node.val}"`);
}
case N.Assignment: {
scope[node.name] = this.eval(node.val);
return scope[node.name];
}
case N.BinaryOp: {
const left = this.eval(node.left);
const right = this.eval(node.right);
switch (node.op) {
// TODO: other ops
case T.IsActually:
return left === right;
case T.Add:
return left + right;
case T.Subtract:
return left - right;
case T.Multiply:
return left * right;
default:
throw new Error(`Runtime error: Unknown binary op ${node.op.toString()}`);
}
}
case N.IfExpr: {
if (this.eval(node.cond)) {
return this.eval(node.ifBody);
}
if (node.elseBody != null) {
return this.eval(node.elseBody);
}
}
case N.ExprGroup: {
let rv = false; // TODO: make null value? make this illegal?
for (const expr of node.exprs) {
rv = this.eval(expr);
}
return rv;
}
case N.ReturnExpr: {
const rv = this.eval(node.val);
throw new ReturnError(rv);
}
case N.ProgEndExpr: {
// do nothing
break;
}
case N.PrintExpr: {
const val = this.eval(node.val);
Runtime.print(val);
return val;
}
default:
console.log(JSON.stringify(node, null, 2));
throw new Error(`Runtime error: Unknown AST Node of type ${
node.type.toString()
}:\n${JSON.stringify(node, null, 2)}`);
}
}
}
// main
try {
const tokens = tokenize(prog);
console.log(tokens);
const nodes = new Parser(tokens).parse();
console.log(nodes);
const env = new Environment();
env.run(nodes);
} catch (e) {
console.error(e);
}