如何对无限列表使用任意值？
我有以下帮助功能：
-- Generator for variable names
instance Arbitrary VarName where
arbitrary = VarName <$> elements ["A", "B", "_0", "_"]
用于以下任务： “定义一个函数 freshVars :: [Varname]，它为您提供以下模式的无限变量名称列表：
[VarName "A",...,VarName "Z",VarName "A0",...,VarName "Z0",VarName “A1”，…，VarName“Z1”，…]”
我该怎么做？我想我没有正确理解任意性。
i have the following help function:
-- Generator for variable names
instance Arbitrary VarName where
arbitrary = VarName <gt; elements ["A", "B", "_0", "_"]
for the following task:
"Define a function freshVars :: [Varname], which gives you an infinite list of variablenames in the following pattern:
[VarName "A",…,VarName "Z",VarName "A0",…,VarName "Z0",VarName "A1",…,VarName "Z1",…]"
How can i do this? i think i dont understand arbitrary properly.
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我们可以使用
["", "0", "1", …, "9", "10", "11", …, "99", …]创建一个列表：有了这个，我们就可以创建一个列表理解，它将构造带有前缀
Character 的字符串，该字符将枚举['A' .. 'Z']并使用其中一项 后缀。我们可以通过列表理解来做到这一点：我将填写
…部分作为练习。We can make a list with
["", "0", "1", …, "9", "10", "11", …, "99", …]with:Now that we have that, we can make a list comprehension that will construct strings with a prefix
Character that will enumerate over['A' .. 'Z']and uses one of the items of the suffix. We can do that with list comprehension:where I leave filling in the
…parts as an exercise.