Type-Level Boolean Logic in TypeScript
This challenge explores the fascinating world of type-level programming in TypeScript. We'll be crafting type aliases that represent boolean values and implementing basic logical operations (AND, OR, NOT) entirely at the type level, without runtime execution. This is useful for enforcing constraints and performing compile-time checks, leading to more robust and predictable code.
Problem Description
The goal is to create a system of type aliases that represent boolean values (true and false) and then implement type-level versions of the logical operators AND, OR, and NOT. These operators should take type arguments representing boolean values and produce a new type representing the result of the logical operation. The core idea is to leverage conditional types and distributive conditional types to achieve this.
What needs to be achieved:
- Define type aliases for
TrueandFalserepresenting boolean values at the type level. - Implement a type alias
And<A extends boolean, B extends boolean>that returnsTrueif bothAandBareTrue, andFalseotherwise. - Implement a type alias
Or<A extends boolean, B extends boolean>that returnsTrueif eitherAorBisTrue, andFalseotherwise. - Implement a type alias
Not<A extends boolean>that returnsTrueifAisFalse, andFalseifAisTrue.
Key Requirements:
- All operations must be performed at the type level. No runtime code should be involved.
- The resulting types should accurately reflect the boolean logic.
- The solution should be type-safe and avoid any type errors.
Expected Behavior:
And<True, True>should evaluate toTrue.And<True, False>should evaluate toFalse.And<False, True>should evaluate toFalse.And<False, False>should evaluate toFalse.Or<True, True>should evaluate toTrue.Or<True, False>should evaluate toTrue.Or<False, True>should evaluate toTrue.Or<False, False>should evaluate toFalse.Not<True>should evaluate toFalse.Not<False>should evaluate toTrue.
Edge Cases to Consider:
- Ensure the types are correctly handled when
TrueorFalseare used as arguments. - Consider how the conditional types behave with different type arguments.
Examples
Example 1:
Input: And<True, True>
Output: True
Explanation: Both inputs are True, so the AND operation results in True.
Example 2:
Input: Or<False, True>
Output: True
Explanation: One of the inputs is True, so the OR operation results in True.
Example 3:
Input: Not<True>
Output: False
Explanation: The input is True, so the NOT operation inverts it to False.
Constraints
- The solution must be written in TypeScript.
- The solution should be concise and readable.
- The solution should not rely on any external libraries or complex type manipulations beyond conditional types and distributive conditional types.
- The solution must be type-safe and not produce any type errors.
Notes
- Think about how conditional types (
A extends B ? C : D) can be used to represent boolean logic. - Distributive conditional types are key to making these operations work correctly with more complex types.
- Start by defining the
TrueandFalsetypes, then build up to the logical operations. - Consider using utility types like
Inferif needed, but the core logic should be based on conditional types.