英文:
guard to check each character in the string
问题
我的函数接受一个字符串，我需要检查每个单独的字符是否为"0"或"1"。如何做到这一点？我尝试过以下方法：
defguard is_bit_string(str)
when is_binary(str) and
byte_size(str) == 1 and
binary_part(str, 0, 1) in ["0", "1"]
defguard is_bit_string(str)
when is_binary(str) and
binary_part(str, 0, 1) in ["0", "1"] and
is_bit_string(binary_part(str, 1, byte_size(str) - 1))
但是结果是守卫不能递归（当我得到以下错误时）：
(CompileError) cannot find or invoke local is_bit_string/1 inside guards. Only macros can be invoked in guards and they must be defined before their invocation. Called as: is_bit_string(binary_part(str, 1, byte_size(str) - 1))
在函数体内检查这一点的问题是，我需要为多个函数检查这个条件，这只会导致不必要的重复。是否有其他方法，以便我不需要在每个函数内部执行这个检查？
英文:
My function takes a string and I need to check each individual character is either "0" or "1".
How to do that?
I have tried this:
defguard is_bit_string(str)
when is_binary(str) and
byte_size(str) == 1 and
binary_part(str, 0, 1) in ["0", "1"]
defguard is_bit_string(str)
# byte_size(str) == 1 and
when is_binary(str) and
binary_part(str, 0, 1) in ["0", "1"] and
is_bit_string(binary_part(str, 1, byte_size(str) - 1))
But turns out gaurd can't be recursive(ig as i get following error:
(CompileError) cannot find or invoke local is_bit_string/1 inside guards. Only macros can be invoked in a guards and they must be defined before their invocation. Called as: is_bit_string(binary_part(str, 1, byte_size(str) - 1))
The problem with checking this inside the function body is I need to check this for multiple functions so it will just be unwanted repition. Are there other ways so that I don't need to do this inside every function?
答案1
得分: 3
我建议使用此函数替代：
def is_bit_string?(str) when is_binary(str) do
str
|> String.graphemes()
|> Enum.all?(fn c -> c in ["0","1"] end)
end
def is_bit_string?(_), do: false
英文:
I will propose using this function instead:
def is_bit_string?(str) when is_binary(str) do
str
|> String.graphemes()
|> Enum.all?(fn c -> c in ["0","1"] end)
end
def is_bit_string?(_), do: false
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