RFR: 8376040: Add prototype "textbook complex" class

[Joe Darcy]

On Thu, 22 Jan 2026 00:35:05 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> First cut at a version of complex numbers using the textbook algorithms for the arithmetic operations. This version is intended for prototyping and _not_ for production use.

Since the HTML markup in the javadoc for the arithmetic methods is hard to read, here is a copy and past of the rendered text:

public static ComplexTextbook add(ComplexTextbook addend, ComplexTextbook augend)

Addition operation, binary "+".

Implementation Requirements:
    The computed sum is equivalent to (a + c) + i·(b + d).


public static ComplexTextbook subtract(ComplexTextbook minuend, ComplexTextbook subtrahend)

Subtraction operation, binary "-".

Implementation Requirements:
    The computed difference is equivalent to (a − c) + i·(b − d).
    

public static ComplexTextbook multiply(ComplexTextbook multiplier, ComplexTextbook multiplicand)

Multiplication operation, "*".

API Note:
    WARNING: while simple, the calculation technique used by this method is subject to spurious underflow and overflow as well as inaccurate component-wise results.
Implementation Requirements:
    The computed product is calculated by (ac − bd) + i·(ad + bc)


public static ComplexTextbook divide(ComplexTextbook dividend, ComplexTextbook divisor)

Division operation, "/".

API Note:
    TODO: Bad numerical things can happen warning...
Implementation Requirements:
    The computed quotient is calculated by (ac + bd)/(c² + d²) + i*(bc − ad)/(c² + d²)

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PR Comment: https://git.openjdk.org/valhalla/pull/1942#issuecomment-3782608915