NBKDoubleWidth+Addition+Digit.swift

//=----------------------------------------------------------------------------=
// This source file is part of the Numberick open source project.
//
// Copyright (c) 2023 Oscar Byström Ericsson
// Licensed under Apache License, Version 2.0
//
// See http://www.apache.org/licenses/LICENSE-2.0 for license information.
//=----------------------------------------------------------------------------=

import NBKCoreKit

//*============================================================================*
// MARK: * NBK x Double Width x Addition x Digit
//*============================================================================*

extension NBKDoubleWidth {
    
    //=------------------------------------------------------------------------=
    // MARK: Transformations x Overflow
    //=------------------------------------------------------------------------=
    
    @_disfavoredOverload @inlinable public mutating func addReportingOverflow(_ other: Digit) -> Bool {
        let minus = other.isLessThanZero as Bool
        if  self.first.addReportingOverflow(UInt(bitPattern: other)) == minus { return false }
        let extra = UInt(bitPattern: minus ? -1 : 1)
        for index in 1 ..< self.lastIndex where self[index].addReportingOverflow(extra) == minus { return false }
        return self.tail.addReportingOverflow(Digit(bitPattern: extra))
    }
    
    @_disfavoredOverload @inlinable public func addingReportingOverflow(_ other: Digit) -> PVO<Self> {
        var partialValue = self
        let overflow: Bool = partialValue.addReportingOverflow(other)
        return PVO(partialValue, overflow)
    }
}