julia - 如何提示用户输入，直到输入在 Julia 中有效

Question

我正在尝试制作一个程序来提示用户输入，直到他们输入特定范围内的数字。

当我输入超出指定范围的字母、符号或数字时，确保代码不会出错的最佳方法是什么？

Answer 1

替代parse , 你可以使用 tryparse :

tryparse(type, str; base)

Like parse, but returns either a value of the requested type, or nothing if the string does not contain a valid number.

相对于parse 的优势在于您可以更清晰地处理错误，而无需求助于try/catch。 ，这将隐藏 block 内引发的所有异常。

例如你可以这样做:

while true
    print("Please enter a whole number between 1 and 5: ")
    input = readline(stdin)
    value = tryparse(Int, input)
    if value !== nothing && 1 <= value <= 5
        println("You entered $(input)")
        break
    else
        @warn "Enter a whole number between 1 and 5"
    end
end

样本运行:

Please enter a whole number between 1 and 5: 42
┌ Warning: Enter a whole number between 1 and 5
└ @ Main myscript.jl:9
Please enter a whole number between 1 and 5: abcde
┌ Warning: Enter a whole number between 1 and 5
└ @ Main myscript.jl:9
Please enter a whole number between 1 and 5: 3
You entered 3