638 lines
18 KiB
JavaScript
638 lines
18 KiB
JavaScript
/* Tabloid: the clickbait headline programming language */
|
|
|
|
/* tokenizer */
|
|
|
|
/**
|
|
* Reads in char or word chunks
|
|
*/
|
|
class Reader {
|
|
constructor(str, base = '') {
|
|
this.base = base;
|
|
this.i = 0;
|
|
this.str = str;
|
|
}
|
|
peek() {
|
|
return this.str[this.i];
|
|
}
|
|
next() {
|
|
return this.str[this.i++];
|
|
}
|
|
hasNext() {
|
|
return this.str[this.i] !== undefined;
|
|
}
|
|
backstep() {
|
|
this.i--;
|
|
}
|
|
readUntil(pred) {
|
|
let result = this.base.slice();
|
|
while (this.hasNext() && !pred(this.peek())) {
|
|
result += this.next();
|
|
}
|
|
return result;
|
|
}
|
|
dropWhitespace() {
|
|
this.readUntil(c => !!c.trim());
|
|
}
|
|
expect(tok) {
|
|
const next = this.next();
|
|
if (next !== tok) {
|
|
throw new Error(`Parsing error: expected ${tok}, got ${next}`);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Split into words for easier tokenization
|
|
* with keywords.
|
|
*/
|
|
class Wordifier {
|
|
constructor(str) {
|
|
this.reader = new Reader(str.trim());
|
|
this.tokens = [];
|
|
}
|
|
wordify() {
|
|
if (this.tokens.length) return this.tokens;
|
|
|
|
while (this.reader.hasNext()) {
|
|
const next = this.reader.next();
|
|
switch (next) {
|
|
case '(': {
|
|
this.tokens.push('(');
|
|
break;
|
|
}
|
|
case ')': {
|
|
this.tokens.push(')');
|
|
break;
|
|
}
|
|
case ',': {
|
|
this.tokens.push(',');
|
|
break;
|
|
}
|
|
case '"':
|
|
case "'": {
|
|
this.wordifyString(next);
|
|
break;
|
|
}
|
|
default: {
|
|
// read until WS
|
|
this.reader.backstep();
|
|
this.tokens.push(this.reader.readUntil(c => {
|
|
return !c.trim() || ['(', ')', ','].includes(c)
|
|
}));
|
|
}
|
|
}
|
|
this.reader.dropWhitespace();
|
|
}
|
|
return this.tokens;
|
|
}
|
|
wordifyString(endChar) {
|
|
let acc = '';
|
|
acc += this.reader.readUntil(c => c == endChar);
|
|
while (acc.endsWith('\\') || !this.reader.hasNext()) {
|
|
acc += this.reader.readUntil(c => c != endChar);
|
|
}
|
|
this.reader.next(); // throw away closing char
|
|
this.tokens.push('"' + acc);
|
|
}
|
|
}
|
|
|
|
const T = {
|
|
LParen: Symbol('LParen'),
|
|
RParen: Symbol('RParen'),
|
|
Comma: Symbol('Comma'),
|
|
DiscoverHowTo: Symbol('DiscoverHowTo'),
|
|
With: Symbol('With'),
|
|
Of: Symbol('Of'),
|
|
WeSaid: Symbol('WeSaid'),
|
|
WhatIf: Symbol('WhatIf'),
|
|
LiesBang: Symbol('LiesBang'),
|
|
EndOfStory: Symbol('EndOfStory'),
|
|
ExpertsClaim: Symbol('ExpertsClaim'),
|
|
ToBe: Symbol('ToBe'),
|
|
YouWontWantToMiss: Symbol('YouWontWantToMiss'),
|
|
IsActually: Symbol('IsActually'),
|
|
And: Symbol('And'),
|
|
Or: Symbol('Or'),
|
|
Add: Symbol('Add'),
|
|
Subtract: Symbol('Subtract'),
|
|
Multiply: Symbol('Multiply'),
|
|
Divide: Symbol('Divide'),
|
|
Modulo: Symbol('Modulo'),
|
|
Beats: Symbol('Beats'), // >
|
|
SmallerThan: Symbol('SmallerThan'), // <
|
|
ShockingDevelopment: Symbol('ShockingDevelopment'),
|
|
PleaseLikeAndSubscribe: Symbol('PleaseLikeAndSubscribe'),
|
|
|
|
// not implemented yet
|
|
StayTuned: Symbol('StayTuned'),
|
|
Unexpectedly: Symbol('Unexpectedly'),
|
|
TotallyRight: Symbol('TotallyRight'),
|
|
CompletelyWrong: Symbol('CompletelyWrong'),
|
|
}
|
|
|
|
const BINARY_OPS = [
|
|
T.IsActually,
|
|
T.And,
|
|
T.Or,
|
|
T.Add,
|
|
T.Subtract,
|
|
T.Multiply,
|
|
T.Divide,
|
|
T.Modulo,
|
|
T.Beats,
|
|
T.SmallerThan,
|
|
];
|
|
|
|
function tokenize(prog) {
|
|
const reader = new Reader(new Wordifier(prog).wordify(), []);
|
|
const tokens = [];
|
|
|
|
while (reader.hasNext()) {
|
|
const next = reader.next();
|
|
switch (next) {
|
|
case 'DISCOVER': {
|
|
reader.expect('HOW');
|
|
reader.expect('TO');
|
|
tokens.push(T.DiscoverHowTo);
|
|
break;
|
|
}
|
|
case 'WITH': {
|
|
tokens.push(T.With);
|
|
break;
|
|
}
|
|
case 'OF': {
|
|
tokens.push(T.Of);
|
|
break;
|
|
}
|
|
case 'WE': {
|
|
reader.expect('SAID');
|
|
tokens.push(T.WeSaid);
|
|
break;
|
|
}
|
|
case 'WHAT': {
|
|
reader.expect('IF');
|
|
tokens.push(T.WhatIf);
|
|
break;
|
|
}
|
|
case 'LIES!': {
|
|
tokens.push(T.LiesBang);
|
|
break;
|
|
}
|
|
case 'END': {
|
|
reader.expect('OF');
|
|
reader.expect('STORY');
|
|
tokens.push(T.EndOfStory);
|
|
break;
|
|
}
|
|
case 'EXPERTS': {
|
|
reader.expect('CLAIM');
|
|
tokens.push(T.ExpertsClaim);
|
|
break;
|
|
}
|
|
case 'TO': {
|
|
reader.expect('BE');
|
|
tokens.push(T.ToBe);
|
|
break;
|
|
}
|
|
case 'YOU': {
|
|
reader.expect('WON\'T');
|
|
reader.expect('WANT');
|
|
reader.expect('TO');
|
|
reader.expect('MISS');
|
|
tokens.push(T.YouWontWantToMiss);
|
|
break;
|
|
}
|
|
case 'IS': {
|
|
reader.expect('ACTUALLY');
|
|
tokens.push(T.IsActually);
|
|
break;
|
|
}
|
|
case 'AND': {
|
|
tokens.push(T.And);
|
|
break;
|
|
}
|
|
case 'OR': {
|
|
tokens.push(T.Or);
|
|
break;
|
|
}
|
|
case 'ADD': {
|
|
tokens.push(T.Add);
|
|
break;
|
|
}
|
|
case 'SUBTRACT': {
|
|
tokens.push(T.Subtract);
|
|
break;
|
|
}
|
|
case 'MULTIPLY': {
|
|
tokens.push(T.Multiply);
|
|
break;
|
|
}
|
|
case 'DIVIDE': {
|
|
tokens.push(T.Divide);
|
|
break;
|
|
}
|
|
case 'MODULO': {
|
|
tokens.push(T.Modulo);
|
|
break;
|
|
}
|
|
case 'BEATS': {
|
|
tokens.push(T.Beats);
|
|
break;
|
|
}
|
|
case 'SMALLER': {
|
|
reader.expect('THAN');
|
|
tokens.push(T.SmallerThan);
|
|
break;
|
|
}
|
|
case 'SHOCKING': {
|
|
reader.expect('DEVELOPMENT');
|
|
tokens.push(T.ShockingDevelopment);
|
|
break;
|
|
}
|
|
case 'PLEASE': {
|
|
reader.expect('LIKE');
|
|
reader.expect('AND');
|
|
reader.expect('SUBSCRIBE');
|
|
tokens.push(T.PleaseLikeAndSubscribe);
|
|
break;
|
|
}
|
|
case 'STAY': {
|
|
reader.expect('TUNED');
|
|
tokens.push(T.StayTuned);
|
|
break;
|
|
}
|
|
case 'UNEXPECTEDLY': {
|
|
tokens.push(T.Unexpectedly);
|
|
break;
|
|
}
|
|
case 'TOTALLY': {
|
|
reader.expect('RIGHT');
|
|
tokens.push(T.TotallyRight);
|
|
break;
|
|
}
|
|
case 'COMPLETELY': {
|
|
reader.expect('WRONG');
|
|
tokens.push(T.CompletelyWrong);
|
|
break;
|
|
}
|
|
case '(': {
|
|
tokens.push(T.LParen);
|
|
break;
|
|
}
|
|
case ')': {
|
|
tokens.push(T.RParen);
|
|
break;
|
|
}
|
|
case ',': {
|
|
tokens.push(T.Comma);
|
|
break;
|
|
}
|
|
default: {
|
|
if (!isNaN(parseFloat(next))) {
|
|
// number literal
|
|
tokens.push(parseFloat(next));
|
|
} else {
|
|
// string or varname
|
|
tokens.push(next);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return tokens;
|
|
}
|
|
|
|
/* parser */
|
|
|
|
const N = {
|
|
NumberLiteral: Symbol('NumberLiteral'),
|
|
StringLiteral: Symbol('StringLiteral'),
|
|
FnDecl: Symbol('FnDecl'),
|
|
FnCall: Symbol('FnCall'),
|
|
Ident: Symbol('Ident'),
|
|
Assignment: Symbol('Assignment'),
|
|
BinaryOp: Symbol('BinaryOp'),
|
|
IfExpr: Symbol('IfExpr'),
|
|
ExprGroup: Symbol('ExprGroup'),
|
|
ReturnExpr: Symbol('ReturnExpr'),
|
|
ProgEndExpr: Symbol('ProgEndExpr'),
|
|
PrintExpr: Symbol('PrintExpr'),
|
|
}
|
|
|
|
class Parser {
|
|
constructor(tokens) {
|
|
this.tokens = new Reader(tokens, []);
|
|
}
|
|
/**
|
|
* Atom
|
|
* Ident
|
|
* NumberLiteral
|
|
* StringLiteral
|
|
* FnCall
|
|
* FnDecl
|
|
* ExprGroup
|
|
*
|
|
* Expression:
|
|
* (begins with atom)
|
|
* BinaryOp
|
|
* Atom
|
|
* (begins with keyword)
|
|
* IfExpr
|
|
* Assignment
|
|
* ReturnExpr
|
|
* ProgEndExpr
|
|
* PrintExpr
|
|
*
|
|
*/
|
|
parse() {
|
|
const nodes = [];
|
|
while (this.tokens.hasNext()) {
|
|
nodes.push(this.expr());
|
|
}
|
|
return nodes;
|
|
}
|
|
expectIdentString() {
|
|
const ident = this.tokens.next();
|
|
if (typeof ident === 'string' && !ident.startsWith('"')) {
|
|
return ident;
|
|
}
|
|
throw new Error(`Parsing error: expected identifier, got ${ident.toString()}`);
|
|
}
|
|
atom() {
|
|
const next = this.tokens.next();
|
|
if (typeof next === 'number') {
|
|
return {
|
|
type: N.NumberLiteral,
|
|
val: next,
|
|
}
|
|
} else if (typeof next === 'string') {
|
|
if (next.startsWith('"')) {
|
|
return {
|
|
type: N.StringLiteral,
|
|
val: next.substr(1),
|
|
}
|
|
}
|
|
const ident = {
|
|
type: N.Ident,
|
|
val: next,
|
|
}
|
|
if (this.tokens.peek() === T.Of) {
|
|
return this.fnCall(ident);
|
|
}
|
|
return ident;
|
|
} else if (next === T.DiscoverHowTo) {
|
|
// fn literal
|
|
const fnName = this.tokens.next();
|
|
if (this.tokens.peek(T.With)) {
|
|
this.tokens.next(); // with
|
|
// with args
|
|
const args = [this.expectIdentString()];
|
|
while (this.tokens.peek() === T.Comma) {
|
|
this.tokens.next(); // comma
|
|
args.push(this.expectIdentString());
|
|
}
|
|
return {
|
|
type: N.FnDecl,
|
|
name: fnName,
|
|
args: args,
|
|
body: this.expr(),
|
|
}
|
|
} else {
|
|
return {
|
|
type: N.FnDecl,
|
|
name: fnName,
|
|
args: [],
|
|
body: this.expr(),
|
|
}
|
|
}
|
|
} else if (next === T.WeSaid) {
|
|
// block
|
|
const exprs = [];
|
|
while (this.tokens.hasNext() && this.tokens.peek() !== T.EndOfStory) {
|
|
exprs.push(this.expr());
|
|
}
|
|
this.tokens.expect(T.EndOfStory);
|
|
return {
|
|
type: N.ExprGroup,
|
|
exprs: exprs,
|
|
};
|
|
}
|
|
|
|
throw new Error(`Parsing error: expected ident, literal, or block, got ${
|
|
next.toString()
|
|
} before ${this.tokens.peek().toString()}`);
|
|
}
|
|
expr() {
|
|
const next = this.tokens.next();
|
|
if (next === T.WhatIf) {
|
|
// if expr
|
|
const cond = this.expr();
|
|
const ifBody = this.expr();
|
|
|
|
let elseBody = null;
|
|
if (this.tokens.peek() == T.LiesBang) {
|
|
this.tokens.next(); // LiesBang
|
|
elseBody = this.expr();
|
|
}
|
|
return {
|
|
type: N.IfExpr,
|
|
cond: cond,
|
|
ifBody: ifBody,
|
|
elseBody: elseBody,
|
|
}
|
|
} else if (next === T.ExpertsClaim) {
|
|
// assignment
|
|
const name = this.expectIdentString();
|
|
this.tokens.expect(T.ToBe);
|
|
const val = this.expr();
|
|
return {
|
|
type: N.Assignment,
|
|
name,
|
|
val,
|
|
}
|
|
} else if (next === T.ShockingDevelopment) {
|
|
// return
|
|
return {
|
|
type: N.ReturnExpr,
|
|
val: this.expr(),
|
|
}
|
|
} else if (next === T.PleaseLikeAndSubscribe) {
|
|
// prog end
|
|
return {
|
|
type: N.ProgEndExpr,
|
|
}
|
|
} else if (next == T.YouWontWantToMiss) {
|
|
// print expr
|
|
return {
|
|
type: N.PrintExpr,
|
|
val: this.expr(),
|
|
}
|
|
}
|
|
|
|
this.tokens.backstep();
|
|
const atom = this.atom();
|
|
if (BINARY_OPS.includes(this.tokens.peek())) {
|
|
// infix binary ops
|
|
// TODO: support operator precedence
|
|
const left = atom;
|
|
const op = this.tokens.next();
|
|
const right = this.atom();
|
|
return {
|
|
type: N.BinaryOp,
|
|
op,
|
|
left,
|
|
right,
|
|
}
|
|
}
|
|
|
|
return atom;
|
|
}
|
|
fnCall(fnNode) {
|
|
this.tokens.expect(T.Of);
|
|
// TODO: support multiple arguments
|
|
const args = [this.expr()];
|
|
return {
|
|
type: N.FnCall,
|
|
fn: fnNode,
|
|
args: args,
|
|
}
|
|
}
|
|
}
|
|
|
|
/* executor (tree walk) */
|
|
|
|
/**
|
|
* Abused (slightly) to easily return values upstack
|
|
*/
|
|
class ReturnError {
|
|
constructor(value) {
|
|
this.value = value;
|
|
}
|
|
unwrap() {
|
|
return this.value;
|
|
}
|
|
}
|
|
|
|
class Environment {
|
|
constructor(runtime) {
|
|
/**
|
|
* Runtime contains the following functions:
|
|
* - print(s)
|
|
*/
|
|
this.runtime = runtime;
|
|
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 --;
|
|
}
|
|
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);
|
|
this.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)}`);
|
|
}
|
|
}
|
|
}
|
|
|