MDex core logic

dex_core

given:
    seller_original_forsale
    seller_original_desired
    seller_forsale
    seller_desired

    buyer_original_forsale
    buyer_original_desired
    buyer_forsale
    buyer_desired

required:
    seller_received (~buyer_spent)
    seller_updated_forsale
    seller_updated_desired          [range > 64 bit]

    buyer_received (~seller_spent)  [range > 64 bit]
    buyer_updated_forsale
    buyer_updated_desired           [range > 64 bit]

    operator <                      [range > 64 bit]
    operator ==                     [range > 64 bit]

----------------------------------------------------

seller_received():
    => min(seller_desired, buyer_forsale)

buyer_received():
    => seller_received * seller_original_forsale / seller_original_desired // round up

seller_updated_forsale():
    => seller_forsale - buyer_received

buyer_updated_forsale():
    => buyer_forsale - seller_received

seller_updated_desired():
    => seller_updated_forsale * seller_original_desired / seller_original_forsale // round up

buyer_updated_desired():
    => buyer_updated_forsale * buyer_original_desired / buyer_original_forsale // round up

operator <():
    => seller_original_desired * buyer_original_forsale < buyer_original_desired * seller_original_forsale

operator ==():
    => seller_original_desired * buyer_original_forsale == buyer_original_desired * seller_original_forsale