为什么while循环随机工作？答案

【问题标题】：Why while loop is working randomly?为什么while循环随机工作？
【发布时间】：2014-04-16 00:41:49
【问题描述】：

当我的 while 循环随机工作时，我感到很困惑？

how.many<-function(fruit, number){
  string<-paste("How many",fruit,"?",sep=" ")
  fruit_number<-readline(string)
  print("fruit number")
  print(fruit_number)
  print("number")
  print(number)
  while(fruit_number > number){
    print("inside while")
    print("fruit number")
    print(fruit_number)
    print("number")
    print(number)
    print("ERROR: too many for the budget")
    string<-paste("How many",fruit,"?",sep=" ")
    fruit_number<-readline(string)
  }
  return(as.numeric(fruit_number))
}

这是我调用此函数的时间：

> source("fruit.R")
> how.many("apple",6)
How many apple ?3
[1] "fruit number"
[1] "3"
[1] "number"
[1] 6
[1] 3
> how.many("apple",10)
How many apple ?9
[1] "fruit number"
[1] "9"
[1] "number"
[1] 10
[1] "inside while"
[1] "fruit number"
[1] "9"
[1] "number"
[1] 10
[1] "ERROR: too many for the budget"
How many apple ?7
[1] "inside while"
[1] "fruit number"
[1] "7"
[1] "number"
[1] 10
[1] "ERROR: too many for the budget"
How many apple ?2
[1] "inside while"
[1] "fruit number"
[1] "2"
[1] "number"
[1] 10
[1] "ERROR: too many for the budget"
How many apple ?1
[1] 1

有什么提示吗？

【问题讨论】：

fruit_number 是一个字符，您尝试将其用作数字。这会导致问题。

标签： r function while-loop

【解决方案1】：

将fruit_number 转换为数字，而不是字符串。

例如

fruit_number <- as.numeric(readline(string))

或

fruit_number <- as.integer(readline(string))

否则数字将作为字符串进行比较，“9”在字符串意义上大于“10”。

【讨论】：