Accumulate

Instructions

Implement the accumulate operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.

Given the collection of numbers:

• 1, 2, 3, 4, 5

And the operation:

• square a number (x => x * x)

Your code should be able to produce the collection of squares:

• 1, 4, 9, 16, 25

Check out the test suite to see the expected function signature.

Restrictions

Keep your hands off that collect/map/fmap/whatchamacallit functionality provided by your standard library! Solve this one yourself using other basic tools instead.

To be more specific, you are not allowed to use any of the built-in LINQ methods.

Laziness test

Since accumulate returns an IEnumerable, its execution is deferred until ToList() it is called on it, which is tested with the Accumulate_is_lazy method.

Hints

This exercise requires you to write an extension method. For more information, see this page.

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Source

Conversation with James Edward Gray II