Add Lerp to IFloatingPointIeee754

[tannergooding]

This resolves #80044

[ghost]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

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Issue Details

---

This resolves #80044

Author:	tannergooding
Assignees:	-
Labels:	area-System.Numerics, new-api-needs-documentation
Milestone:	-

[dakersnar]

LGTM. Anything notably tricky that could use a triple check?

[tannergooding]

LGTM. Anything notably tricky that could use a triple check?

Not really, this is a really straightforward API with a trivial implementation.

The biggest "gotcha" is ensuring that it is implemented as (value1 * (1.0f - amount)) + (value2 * amount) and not as value1 + ((value2 - value1) * amount)

The two algorithms are mathematically "equivalent" (assuming amount is between 0 and 1, inclusive). However, they produce different results for various edge cases when considering floating-point values and only the former is guaranteed to correctly return value2 when amount == 1.0f

[dakersnar]

The floating-point-specific behavior for this functionality is not specified in the IEEE spec, correct? Given that, I assume we are just following common sense and industry standards when deciding how these edge cases are handled?

[tannergooding]

Correct