Implement Curried Add Function | Dataford Interview Questions

Blinkit frontend utilities may expose the same operation through multiple calling styles. Implement an add function so that both add(a, b) and add(a)(b) return the sum of a and b.

The curried form must return a callable after receiving the first operand. The returned callable accepts the second operand and produces the same numeric result as the direct form. Do not modify global state, and each invocation must create an independent closure.

Formal Specification

Implement add(a, b=None) in Python:

When b is provided, return a + b.
When b is omitted, return a callable that accepts one argument and returns a + b.
Inputs are integers, including negative values and zero.

Constraints

a and b are integers
-10^9 <= a, b <= 10^9
Both direct and curried forms must return the same sum
Each invocation must be independent

Function Signature

def add(a, b=None):

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