lua 计算器无法正常工作

Question

当我输入除 + - * 或 / 以外的其他内容时，它仍然只在最后打印出所有内容，它说 "invalid"

print("+-*/?")
method = io.read()
if method == "+" or "-" or "*" or "/" then
  print("type a number")
  num1 = io.read()
  print("type another number")
  num2 = io.read()
elseif method ~= "+" or "-" or "*" or "/" then
  print("invalid")
end

if method == "+" then
  plusnum = num1 + num2
  print(plusnum)
elseif method == "-" then
  minusnum = num1 - num2
  print(minusnum)
elseif method == "*" then
  timesnum = num1 * num2
  print(timesnum)
elseif method == "/" then
  percentnum = num1 / num2
  print(percentnum)
end

Answer 1

你的错误在下面一行：

if method == "+" or "-" or "*" or "/" then

来自Lua 5.3 Reference Manual 3.4.5 Logical Operators

The logical operators in Lua are and, or, and not. Like the control structures (see §3.3.4), all logical operators consider both false and nil as false and anything else as true.

因此，无论使用何种方法，您的 if 语句的条件将始终评估为 true，因为您 or 至少有一个 true 值，结果为 true.

正如 Egor 已经提到的，您必须使用：

if method == "+" or method == "-" or method == "*" or method == "/" then

lua 计算器无法正常工作

lua calculator not working properly

lua

calculator