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Computr.swift

import Foundation

struct Computr {
    typealias Integer = Int
    typealias Address = UnsafeMutablePointer<Integer>
    var ic: Address = Address.allocate(capacity: 1)
    var eax: Integer = 0
    var memory = Address.allocate(capacity: 10)

    mutating func addr(at index: Int) -> Address {
        return memory.advanced(by: index)
    }
    struct Instruction {
        enum Operation: Integer {
            case move, add
        }
        let op: Operation
        let from: Address
        let to: Address

        func execute() {
            switch op {
            case .move:
                to.pointee = from.pointee
            case .add:
                to.pointee = to.pointee + from.pointee
            }
        }
    }

    mutating func execute(count: Int) {
        for _ in 0..<count {
            ic.withMemoryRebound(to: Instruction.self, capacity: 1) { buff in
                buff.pointee.execute()
            }
            ic = ic.advanced(by: MemoryLayout<Instruction>.size)
        }
    }
}


var computr = Computr()

var ONE: Int = 1
var TEN: Int = 10

var addInstructions: [Computr.Instruction] = [
    .init(op: .move, from: &TEN, to: &computr.eax),
    .init(op: .add, from: &ONE, to: &computr.eax),
    .init(op: .move, from: &computr.eax, to: computr.addr(at: 0)),
]
computr.ic = addInstructions.withUnsafeMutableBufferPointer { buffer in
    let address = buffer.baseAddress?.withMemoryRebound(to: Computr.Integer.self, capacity: addInstructions.capacity) { $0 }
    return address!
}
computr.execute(count: 2)