30:T4a8,md` \`tiddlylisp.js\` is a JavaScript implementation of Michael Nielsen's [tiddlylisp](https://github.com/mnielsen/tiddlylisp), which is based on Peter Norvig's [lispy](http://norvig.com/lispy.html). I thought it would be fun to provide a REPL to play around with the language -- evaluate expressions, hack on it, etc. There are definitely bugs; please let me know if you find any! To learn what the language is capable of (and why it exists), read [Lisp as the Maxwell’s equations of software](http://www.michaelnielsen.org/ddi/lisp-as-the-maxwells-equations-of-software/). As an example, the following is a recursive definition of the factorial function: > \`\`\` (define fac! (lambda (n) (if (= n 1) 1 (* n (fac! (- n 1)))))) \`\`\` The code box below lets you define multiline functions, and it already contains the expression that defines \`fac!\`. Click the "Evaluate" button to evaluate the expression in the code box and add it to the environment. Then, try out the function in the REPL. > \`\`\` tiddlylisp> (fac! 4) 24 tiddlylisp> \`\`\` To extend the language, try adding a new procedure, either via the code box or directly to the \`env\` below. Then use it in the REPL! `31:Taf3,tleval = (x, env) => { // Evaluate an expression in an environment // console.log({x: x, env: env}) const helper = (x, env) => { if (typeof(x) === "string") { // variable reference return env.find(x)[x] } else if (!Array.isArray(x)) { // constant literal return x } else if (x[0] === "quote" || x[0] === "q") { // (quote exp) or (q exp) const [_, exp] = x return exp } else if (x[0] == "atom?") { // (atom? exp) const [_, exp] = x return !Array.isArray(helper(exp, env)) } else if (x[0] === "eq?") { // (eq? exp1 exp2) const [_, exp1, exp2] = x const v1 = helper(exp1, env) const v2 = helper(exp2, env) return (!Array.isArray(v1) && (v1 === v2)) } else if (x[0] === "car") { // (car exp) const [_, exp] = x // console.log(helper(exp, env)) return helper(exp, env)[0] } else if (x[0] === "cdr") { // (cdr exp) const [_, exp] = x return helper(exp, env).slice(1) } else if (x[0] === "cons") { // (cons exp1 exp2) const [_, exp1, exp2] = x let res = helper(exp2, env) res.unshift(helper(exp1, env)) return res } else if (x[0] === "cond") { // (cond (p1 e1) ... (pn en)) const ps = x.slice(1) ps.forEach((p, e) => { if (helper(p, env)) { return helper(e, env) } }) } else if (x[0] === "null?") { // (null? exp) const [_, exp] = x const v = helper(exp, env) return (Array.isArray(v) && v.length === 0) } else if (x[0] === "if") { // (if text conseq alt) const [_, test, conseq, alt] = x if (helper(test, env)) { return helper(conseq, env) } else { return helper(alt, env) } } else if (x[0] === "set!") { // (set! var exp) const [_, vari, exp] = x env.find(vari)[vari] = helper(exp, env) } else if (x[0] === "define") { // (define var exp) const [_, vari, exp] = x env[vari] = helper(exp, env) } else if (x[0] === "lambda") { // (lambda (var*) exp) const [_, vars, exp] = x // console.log({vars: vars, exp: exp}) return ( (...args) => { const newEnv = new Env(vars, args, env) // console.log({newEnv: newEnv}) return helper(exp, new Env(vars, args, env)) } ) } else if (x[0] === "begin") { // (begin expr*) let val x.slice(1).forEach((exp) => val = helper(exp, env)) return val } else { // A built-in procedure call // (proc exp*) const exps = x.map(exp => helper(exp, env)) const proc = exps.shift() return proc(...exps) } } return helper(x, env) }32:T57d,terminal = { term.reset() term.prompt = () => { term.write("\r\ntiddlylisp> ") } term.write("Welcome to tiddlylisp.js!") term.prompt() let command = "" term.onKey(function({key, domEvent}) { const ev = domEvent const buffer = term.buffer.active // console.log(buffer) // console.log(ev) const printable = !ev.altKey && !ev.altGraphKey && !ev.ctrlKey && !ev.metaKey if (ev.keyCode === 13) { // Handle pressing the enter key const line = buffer.getLine(buffer.baseY + buffer.cursorY) let input = line.translateToString(true, 12) try { const output = tleval(parse(input), env) console.log({output: toString(output)}) if (toString(output) !== "undefined") { term.write("\r\n" + toString(output)) } } catch (err) { term.write("\r\nError: " + err) } term.prompt() } else if (ev.keyCode === 8) { // Do not delete the prompt if (buffer.cursorX > 12) { term.write("\b \b") } } else if (ev.code === "ArrowLeft") { if (buffer.cursorX > 12) { term.write(key) } } else if (ev.code === "ArrowUp" || ev.code === "ArrowDown") { // nop } else if (printable) { term.write(key) } }) // term.onData(function(data) { // console.log(data) // term.write(data) // }) }33:[] 2e:{"title":"tiddlylisp.js","cells":[{"id":545,"value":"html`\n

`tiddlylisp.js`

\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":24,"value":"repl = html`\n

\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":0,"value":"$30","pinned":false,"hidden":false,"mode":"ojs"},{"id":561,"value":"md`## Define longer functions`","pinned":false,"hidden":false,"mode":"ojs"},{"id":591,"value":"viewof evalButton = button({value: \"Evaluate\"})","pinned":false,"hidden":false,"mode":"ojs"},{"id":635,"value":"mutable evalResult = \"\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":572,"value":"longerInput = {\n let div = DOM.element('div');\n div.style.border = '1px solid #000';\n div.style.height = '200px';\n return div;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":540,"value":"md`## The environment`","pinned":false,"hidden":false,"mode":"ojs"},{"id":395,"value":"class Env {\n constructor(vars = [], args = [], outer = null) {\n // this.env = {}\n if (vars.length !== 0) {\n if (vars.length === args.length) {\n vars.forEach((vari, i) => this[vari] = args[i])\n }\n }\n this.outer = outer \n }\n \n find(vari) {\n // Find the innermost Env where var appears.\n if (this.hasOwnProperty(vari)) {\n return this\n } else {\n try { return this.outer.find(vari) }\n catch (err) { throw `Symbol \"${vari}\" wasn't found in the environment` }\n }\n }\n \n update(obj) {\n Object.keys(obj).forEach(key => {\n this[key] = obj[key]\n })\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":399,"value":"mutable env = {\n let env = new Env()\n \n // You can add your own defaults to the environment here\n // env.update({\n // a: 1,\n // b: 2,\n // c: 1034\n // })\n \n env.update({\n \"+\": (...args) => {\n let total = args.shift()\n args.forEach(num => total = total + num)\n return total\n },\n \"-\": (...args) => {\n let total = args.shift()\n args.forEach(num => total = total - num)\n return total\n },\n \"*\": (...args) => {\n let total = args.shift()\n args.forEach(num => total = total * num)\n return total\n },\n \"/\": (expr1, expr2) => {\n return expr1 / expr2\n },\n \"<\": (expr1, expr2) => {\n return expr1 < expr2\n },\n \">\": (expr1, expr2) => {\n return expr1 > expr2\n },\n \"<=\": (expr1, expr2) => {\n return expr1 <= expr2\n },\n \">=\": (expr1, expr2) => {\n return expr1 >= expr2\n },\n \"=\": (expr1, expr2) => {\n return expr1 == expr2\n }\n })\n \n env.update({\"true\": true, \"false\": false})\n \n return env\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":177,"value":"md`## Parsing`","pinned":false,"hidden":false,"mode":"ojs"},{"id":9,"value":"parse = (string) => { return readFrom(tokenize(string)) }","pinned":false,"hidden":false,"mode":"ojs"},{"id":180,"value":"tokenize = (string) => {\n let tokenized = string.replace(/\$/g, \" ( \").replace(/\$/g, \" ) \").replace(/\\t/g, \"\").replace(/\\n/g, \"\").split(\" \")\n tokenized = tokenized.filter((token) => token !== \"\")\n // console.log(tokenized)\n return tokenized\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":196,"value":"readFrom = (tokens) => {\n // Read an expression from a sequence of tokens.\n const helper = (tokens) => {\n if (tokens.length === 0) {\n throw 'unexpected EOF while reading'\n }\n\n let token = tokens.shift()\n\n if (token === '(') {\n let L = []\n while (tokens[0] !== ')') {\n L.push(helper(tokens))\n }\n tokens.shift()\n return L\n }\n else if (token === ')') {\n throw SyntaxError('unexpected )')\n }\n else {\n return atom(token)\n }\n }\n return helper(tokens)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":200,"value":"atom = (token) => {\n // Numbers become numbers; every other token is a symbol.\n // First, try to parse as an int\n let atom = parseFloat(token)\n // console.log({parseFloat: atom})\n if (!isNaN(atom)) {\n return atom\n } else {\n atom = String(token)\n // console.log({String: atom})\n return String(token)\n }\n}\n","pinned":false,"hidden":false,"mode":"ojs"},{"id":247,"value":"toString = (expression) => {\n // Convert from tokenized list back to a string\n const helper = (expression) => {\n if (!Array.isArray(expression)) {\n return String(expression)\n } else {\n return \"(\" + expression.map(helper).join(\" \") + \")\"\n }\n }\n return helper(expression)\n} ","pinned":false,"hidden":false,"mode":"ojs"},{"id":261,"value":"md`## Evaluating`","pinned":false,"hidden":false,"mode":"ojs"},{"id":12,"value":"$31","pinned":false,"hidden":false,"mode":"ojs"},{"id":627,"value":"viewof evalButton.onclick = (e) => {\n mutable evalResult = tleval(parse(editor), env)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":267,"value":"md`## Error handling`","pinned":false,"hidden":false,"mode":"ojs"},{"id":5,"value":"handle_error = (err) => {\n console.error(\"An error occurred: \" + err)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":270,"value":"md`## Defining the terminal`","pinned":false,"hidden":false,"mode":"ojs"},{"id":26,"value":"$32","pinned":false,"hidden":false,"mode":"ojs"},{"id":486,"value":"KEYS = ({\n LEFT_ARROW: '\\x1b[D',\n UP_ARROW: '\\x1b[A',\n RIGHT_ARROW: '\\x1b[C',\n DOWN_ARROW: '\\x1b[B',\n CONTROL_U: '\\x15',\n ENTER: '\\r',\n DELETE: '\\x7F',\n})","pinned":false,"hidden":false,"mode":"ojs"},{"id":66,"value":"term = {\n while (repl.firstChild) { repl.removeChild(repl.firstChild) }\n let term = new xterm.Terminal();\n term.open(repl);\n return term\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":32,"value":"xtermCSS = html`\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":22,"value":"xterm = require(\"https://unpkg.com/xterm@4.7.0/lib/xterm.js\")","pinned":false,"hidden":false,"mode":"ojs"},{"id":564,"value":"md`## Codemirror`","pinned":false,"hidden":false,"mode":"ojs"},{"id":570,"value":"editor = {\n while (longerInput.firstChild) { longerInput.removeChild(longerInput.firstChild); }\n let editor = CodeMirror(longerInput, {\n mode: \"application/lisp\"\n });\n editor.setValue(`(define fac!\n (lambda (n)\n (if (= n 1)\n 1\n (* n (fac! (- n 1))))))`);\n editor.setSize(width - 20, 200);\n return Generators.observe(change => {\n change(editor.getValue());\n editor.on('change', (cm, val) => {\n change(editor.getValue());\n });\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":567,"value":"CodeMirror = require('https://unpkg.com/codemirror@5.32.0/lib/codemirror').then(CodeMirror => {\n // this is a bit tricky: we don't just require('codemirror') above, because\n // the sparql mode requires a slightly different path (codemirror instead of codemirror.js)\n // and we need the mode to modify the right instance\n return require('https://unpkg.com/codemirror@5.32.0/mode/sparql/sparql.js').then(() => CodeMirror);\n})","pinned":false,"hidden":false,"mode":"ojs"},{"id":578,"value":"stylesheet = html``","pinned":false,"hidden":false,"mode":"ojs"},{"id":583,"value":"md`## Other utilities`","pinned":false,"hidden":false,"mode":"ojs"},{"id":587,"value":"import {button} from \"@jashkenas/inputs\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":647,"value":"styles = html`\n