[obsidian] vault backup: 2023-11-25 02:30:30[
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@ -8,23 +8,9 @@
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(let double (lambda (x) (* x x)) (double 6))
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```
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まあプリミティブ演算は四則演算だけで再帰関数は自力で定義
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```lisp
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(let fix
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(lambda (f)
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(
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(lambda (x) (f (lambda(y) (x x y))))
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(lambda (x) (f (lambda(y) (x x y))))
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)
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)
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(let fact
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(fix (lambda (f) (lambda (n) (if n (* n (f (- n 1))) 1) ) ))
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(fact 10)
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)
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)
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%% 一行に直す %%
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(let fix (lambda (f) ( (lambda (x) (f (lambda(y) (x x y)))) (lambda (x) (f (lambda(y) (x x y))))))(let fact (fix (lambda (f) (lambda (n) (if n (* n (f (- n 1))) 1) ) ))(fact 10)))
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```
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ただ再帰は今のところ難しい。多分ListとAtomの区別がきちんとできてないせいで不動点コンビネータがきちんと動かない。
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あくまで雰囲気重視で、ということなのだが、結果的にコードが短いため初学者にわかりやすいかと言われると、かなりコメントを足していかないと読めなさそう。
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```js
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const reader = require("readline").createInterface({
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@ -65,11 +51,7 @@ const parse = (tokens) => {
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}
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return next_res
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}
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const read = (str) => {
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const res = parse(tokenize(str));
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return res
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}
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const read = (str) => parse(tokenize(str));
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const binop = (args, fn) => fn(args[0], args[1]);
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@ -78,7 +60,8 @@ const env = {
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"+": args => binop(args, (a, b) => a + b),
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"-": args => binop(args, (a, b) => a - b),
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"*": args => binop(args, (a, b) => a * b),
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"/": args => binop(args, (a, b) => a / b)
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"/": args => binop(args, (a, b) => a / b),
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"if": args => args[0] ? args[1] : args[2]
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}
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const try_find = (name, env) => {
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@ -92,30 +75,34 @@ const try_find = (name, env) => {
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}
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}
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const eval = (expr, env) => {
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if (expr ==null){
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return null;
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}
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if (!Array.isArray(expr)) {
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return !isNaN(parseFloat(expr)) ? parseFloat(expr) : try_find(expr, env)
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} else {
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const op = expr.shift();
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switch (op) {
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case 'let': {
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let res = eval(expr[1], env);
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let newenv = { "parent": env };
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env[expr[0]] = eval(expr[1], newenv);
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return eval(expr[2], env)
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newenv[expr[0]] = res;
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return eval(expr[2], newenv)
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}
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case 'lambda': return ['closure', expr[0], expr[1], env]//ids,body,env
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default: {
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let fn = try_find(op, env);
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let fn = eval(op, env);
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if (fn) {
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if (Array.isArray(fn) && fn[0] === "closure") {
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if (Array.isArray(fn) && fn[0] === "closure") {//closure
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for (let i = 0; i < fn[1].length; i++) {
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fn[3][fn[1][i]] = expr[i]
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fn[3][fn[1][i]] = eval(expr[i],env)
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}
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return eval(fn[2], fn[3])
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} else {
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} else {//extern function
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return fn(expr.map(e => eval(e, env)))
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}
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} else {
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console.error(`symbol ${op} not found`)
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return fn
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}
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}
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}
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@ -1,6 +1,6 @@
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#programming-language #compiler-design
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[[Node.jsで100行で書くLISP風ラムダ計算]]
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[[Node.jsで約100行で書くLISP風ラムダ計算]]
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[Write a JavaScript Parser in Rust](https://oxc-project.github.io/javascript-parser-in-rust/ja/docs/intro/)
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