需要一种用户输入类型的方法：命令行程序的双精度[重复]

Posted 2023-02-23

【中文标题】需要一种用户输入类型的方法：命令行程序的双精度[重复]

【英文标题】：Need a way for user to input type:double for command line program [duplicate]

【发布时间】：2018-02-21 21:29:15

【问题描述】：

我最近开始学习 C++ 和 Swift。我已经用 C++ 编写了一些程序，并决定尝试将其中一个程序翻译成 Swift。我遇到了一个问题。当我尝试使用readline() 在 Swift 中从用户那里获取输入时，它会将数字保存为字符串而不是 Double。结果，每当我尝试计算时，我的程序中都会出现错误。

二元运算符“*”不能应用于“Double”和“String”类型的操作数

我已尝试在 Internet 上搜索解决此问题的方法，但我找到的所有说明都已过时。如果有人可以提供帮助，将不胜感激。

下面是我将 C++ 代码翻译成 Swift 的尝试。

/* Calculate and display the circumference of a circular gazebo and the price of the railing materials for it. */

import Foundation

//Declare Name Constants
let PI : Double = 3.141593

//Input
print("Enter the diameter (in feet) of the gazebo: ")
let gazeboDiameter = (readLine()!)

print ("Enter the price (per foot) of railing material: ")
let priceOfRailing = ((readLine()!)

// Calculate circumference and price
let circumference = PI * gazeboDiameter
let costOfGazebo = circumference * priceOfRailing

//Output
print("The Diameter of the Gazebo is: " (gazeboDiameter))
print("The price (per foot) of the railing material is: "(costOfGazebo))
print("The circumference of the gazebo is: " (circumference))
print("The price of the railing will be: $"(costOfGazebo))

【问题讨论】：

问题是什么？请考虑删除 C++ 部分。

【参考方案1】：

readLine(strippingNewline:) 返回一个字符串类型的对象。 因此，您必须尝试从 String 转换为 double。 你的程序就变成了：

//SWIFT
/* Calculate and display the circumference of a circular gazebo and the price of the railing materials for it. */

import Foundation

//Declare Variables
var gazeboDiameter: Double = 0.0
var priceOfRailing: Double = 0.0
var circumference: Double = 0.0
var costOfGazebo: Double = 0.0

//Input
print("Enter the diameter (in feet) of the gazebo: ")
gazeboDiameter = Double(readLine()!)!

print ("Enter the price (per foot) of railing material: ")
priceOfRailing = Double(readLine()!)!

// Calculate circumference and price
circumference = Double.pi * gazeboDiameter
costOfGazebo = circumference * priceOfRailing

//Output
print("The Diameter of the Gazebo is: \(gazeboDiameter)")
print("The price (per foot) of the railing material is: \(costOfGazebo)")
print("The circumference of the gazebo is: \(circumference)")
print("The price of the railing will be: $\(costOfGazebo)")