mal/es6/step1_read_print.js

import { readline } from './node_readline'
import { BlankException, read_str } from './reader'
import { pr_str } from './printer'

// read
const READ = (str) => read_str(str)

// eval
const EVAL = (ast, env) => ast

// print
const PRINT = (exp) => pr_str(exp, true)

// repl
const REP = (str) => PRINT(EVAL(READ(str), {}))

while (true) {
    let line = readline('user> ')
    if (line == null) break
    try {
        if (line) { console.log(REP(line)); }
    } catch (exc) {
        if (exc instanceof BlankException) { continue; }
        if (exc.stack) { console.log(exc.stack); }
        else           { console.log(`Error: ${exc}`); }
    }
}