From f9d07de20457ede9f88130e55f5f86f48e04b989 Mon Sep 17 00:00:00 2001 From: "David R. Pugh" Date: Tue, 29 May 2018 12:50:20 +0300 Subject: [PATCH] Preferences should be contravariant in its type parameter --- src/main/scala/org/economicsl/matching/Preferences.scala | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/main/scala/org/economicsl/matching/Preferences.scala b/src/main/scala/org/economicsl/matching/Preferences.scala index f6ee9fb..b520749 100644 --- a/src/main/scala/org/economicsl/matching/Preferences.scala +++ b/src/main/scala/org/economicsl/matching/Preferences.scala @@ -21,9 +21,9 @@ package org.economicsl.matching * @tparam A the type over which the `Ordering` is defined. * @note any `Ordering` implies a `max` operator that can be used as an `operator` to compare two `Tradable` instances. */ -trait Preferences[A] { +trait Preferences[-A] { /** An `Ordering` defined over a particular type of `A`. */ - def ordering: Ordering[A] + def ordering[B <: A]: Ordering[B] }