建立编程语言

class Magenta {  constructor(codes) {    this.codes = codes  }  run() {    console.log(this.codes)  }} // For now, we are storing codes in a string variable called `codes`// Later, we will read codes from a fileconst codes =`print "hello world"print "hello again"`const magenta = new Magenta(codes)magenta.run()

class Magenta {  constructor(codes) {    this.codes = codes  }  tokenize() {    const length = this.codes.length    // pos keeps track of current position/index    let pos = 0    let tokens = []    const BUILT_IN_KEYWORDS = ["print"]    // allowed characters for variable/keyword    const varChars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_'    while (pos < length) {      let currentChar = this.codes[pos]      // if current char is space or newline,  continue      if (currentChar === " " || currentChar === "\n") {        pos++        continue      } else if (currentChar === '"') {        // if current char is " then we have a string        let res = ""        pos++        // while next char is not " or \n and we are not at the end of the code        while (this.codes[pos] !== '"' && this.codes[pos] !== '\n' && pos < length) {          // adding the char to the string          res += this.codes[pos]          pos++        }        // if the loop ended because of the end of the code and we didn't find the closing "        if (this.codes[pos] !== '"') {          return {            error: `Unterminated string`          }        }        pos++        // adding the string to the tokens        tokens.push({          type: "string",          value: res        })      } else if (varChars.includes(currentChar)) {        let res = currentChar        pos++        // while the next char is a valid variable/keyword charater        while (varChars.includes(this.codes[pos]) && pos < length) {          // adding the char to the string          res += this.codes[pos]          pos++        }        // if the keyword is not a built in keyword        if (!BUILT_IN_KEYWORDS.includes(res)) {          return {            error: `Unexpected token ${res}`          }        }        // adding the keyword to the tokens        tokens.push({          type: "keyword",          value: res        })      } else { // we have a invalid character in our code        return {          error: `Unexpected character ${this.codes[pos]}`        }      }    }    // returning the tokens    return {      error: false,      tokens    }  }  run() {    const {      tokens,      error    } = this.tokenize()    if (error) {      console.log(error)      return    }    console.log(tokens)  }}

class Magenta {  constructor(codes) {    this.codes = codes  }  tokenize(){    /* previous codes for tokenizer */  }  parse(tokens){    const len = tokens.length    let pos = 0    while(pos < len) {      const token = tokens[pos]      // if token is a print keyword      if(token.type === "keyword" && token.value === "print") {        // if the next token doesn't exist        if(!tokens[pos + 1]) {          return console.log("Unexpected end of line, expected string")        }        // check if the next token is a string        let isString = tokens[pos + 1].type === "string"        // if the next token is not a string        if(!isString) {          return console.log(`Unexpected token ${tokens[pos + 1].type}, expected string`)        }        // if we reach this point, we have valid syntax        // so we can print the string        console.log('\x1b[35m%s\x1b[0m', tokens[pos + 1].value)        // we add 2 because we also check the token after print keyword        pos += 2      } else{ // if we didn't match any rules        return console.log(`Unexpected token ${token.type}`)      }    }  }  run(){    const {tokens, error} = this.tokenize()    if(error){      console.log(error)      return    }    this.parse(tokens)  }}

// importing file system moduleconst fs = require('fs')//importing path module for convenient path joiningconst path = require('path')class Magenta{  constructor(codes){    this.codes = codes  }  tokenize(){    /* previous codes for tokenizer */ }  parse(tokens){    /* previous codes for parse method */ }  run(){    /* previous codes for run method */  }} // Reading code.m file// Some text editors use \r\n for new line instead of \n, so we are removing \rconst codes = fs.readFileSync(path.join(__dirname, 'code.m'), 'utf8').toString().replace(/\r/g, "")const magenta = new Magenta(codes)magenta.run()