如何创建('a, 'b) myList
仅以 开头type1
且仅以 结尾的新数据类型type2
?
例如 :
[4,5,6,8,9.3,4.2,5.1] (*starts with int ends with real*)
[“hi”, “hello”, true, false] (*starts with string ends with bool*)
[4,5,6,8,9.3,4.2,5] (*can't because starts with int and ends with int*)