1. If an F# function has type 'a - > 'b when 'a : comparison, which of the following is not a legal type for it? Select one:

A. (float - > float) - > bool

B. string - > (int - > int)

C. int - > int

D. int list - > bool list

B. string - > (int - > int)

Explanation:

We are going to perform comparison operations '->'. It is important to notice that the comparison operation gives us a bool value (True or False) and the comparison operation is legal if and only if the data types to be compared are the same.

Example:

int (4) - >int (5) False

int (4) - >int (4) True

int (4) - >string (4) Error, data types don't match

For this reason:

A. Is legal because float - > float evaluates to True, True is a boolean value and bool - > bool is legal because both are the same data type. B. Is illegal because int - > int evaluates to True, True is a boolean value and string is not a boolean (string - > bool). C. Is legal because int is the same type than int. D. Is legal because the list is the same type than list regardless it's content.

Note:

The operations inside parentheses are evaluated first.

List is a type by itself regardless of its content.