为什么Math.js在计算表达式时默认以乘法为运算符？

Question

//Require module
const express = require('express');
const { evaluate, compile, parse } = require('mathjs');
// Express Initialize
const app = express();
const port = 8000;
app.listen(port, () => {
    console.log('listen port 8000');
 
})

//create api
app.get('/hello_world', (req, res) => {
    const expression = "A B A";
    console.log(expression.length);
    let response;
    const scope = {
        A: 5,
        B: 4
    }

    try {
        const parsedExp = parse(expression);
        const compiled = parsedExp.compile();
        const result = compiled.evaluate(scope);
        response = {
            "expression": parsedExp.toString(),
            "variables": parsedExp.args,
            "result": result
        }
          console.log("success");
          res.send(JSON.stringify(response));
    } catch (error) {
        console.log(error);    
        res.send(JSON.stringify(error));
    }
})

代码和计算工作正常。但它默认采用乘法。有没有一种方法可以阻止这种默认行为，并向用户抛出一条错误消息，请用户输入所需的运算符？

我什至尝试使用正常的 javascript 代码与 space 分开并尝试检查 +,-,*,/,^ 运算符但用户仍然可以给出多个 space 然后写入另一个变量

感谢帮助

Answer 1

目前没有选项可以禁用 implicit multiplication, but there is a (currently open) github issue for that. And in the comments of that issue there is a workaround 查找任何隐式乘法并在找到时抛出错误。

try {
  const parsedExp = parse(expression);
  parsedExp.traverse((node, path, parent) => {
    if (node.type === 'OperatorNode' && node.op === '*' && node['implicit']) {
      throw new Error('Invalid syntax: Implicit multiplication found');
    }
  });
  ...
} catch (error) {
  console.log(error);
  res.send(JSON.stringify(error));
}

为什么Math.js在计算表达式时默认以乘法为运算符？

Why Math.js default takes multiply as operator when calculation an expression?

javascript

math

node.js

mathjs