ひとつのリスト中に違う型の値を含めることはできない。
Prelude> [1,2,'a']
<interactive>:1:1:
No instance for (Num Char)
arising from the literal 1' at <interactive>:1:1
Probable fix: add an instance declaration for (Num Char)
In the list element: 1
In the definition of
it': it = [1, 2, 'a']
当然連結もダメ。
Prelude> [1,2,3] ++ ['a','b','c'] <interactive>:1:1: No instance for (Num Char) arising from the literal1' at <interactive>:1:1 Probable fix: add an instance declaration for (Num Char) In the list element: 1 In the first argument of
(++)', namely[1, 2, 3]' In the definition of
it': it = [1, 2, 3] ++ ['a', 'b', 'c']