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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -46,12 +46,14 @@ otherwise it is ignored. The :MAGNITUDE argument is mandatory." (assert (shiftf magnitudep t) (magnitude) "The :MAGNITUDE argument was not provided.") (setf outcome (ccase keyword (:vs (assert (shiftf outcomep t) (outcome) "The :OUTCOME argument was not provided.") outcome) (:beats 1) (:draws 1/2) (:loses-to 0))) (when (and (not (eql keyword :vs)) outcomep) (warn "The :OUTCOME argument has been ignored.")) (let ((elo-change (elo-change player opponent outcome magnitude))) -
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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -1,6 +1,8 @@ (defpackage :elo (:use :cl)) (in-package :elo) (defvar *expected-outcome-fun* nil "This is used to supply an alternative function for calculating the expected outcome of a game (whose -
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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -0,0 +1,56 @@ (defpackage :elo (:use :cl)) (defvar *expected-outcome-fun* nil "This is used to supply an alternative function for calculating the expected outcome of a game (whose arguments are the Elo scores of the two players, and returns a number between 0 and 1). You shouldn't change this unless you know what you're doing.") (declaim (type (or null (function (real real) (real 0 1))) *expected-outcome-fun*)) (defun expected-outcome (player-elo opponent-elo) "The default function used for determining the expected outcome of a game." (check-type player-elo real) (check-type opponent-elo real) (the (real 0 1) (/ (1+ (expt 10 (/ (- opponent-elo player-elo) 400)))))) (defun elo-change (player opponent outcome magnitude) "Calculates the number of Elo points gained or lost by PLAYER after a game against OPPONENT with the given OUTCOME." (check-type player real) (check-type opponent real) (check-type outcome (real 0 1)) (check-type magnitude (real (0))) (* magnitude (- outcome (funcall (or *expected-outcome-fun* #'expected-outcome) player opponent)))) (defun game (player keyword opponent &key (outcome nil outcomep) (magnitude nil magnitudep)) "Returns the Elo scores of PLAYER and OPPONENT after a game. The KEYWORD argument can be any of :BEATS, :DRAWS, :LOSES-TO, or :VS. When the KEYWORD argument is :VS, the :OUTCOME is used to specify the outcome of the game and must be provided, otherwise it is ignored. The :MAGNITUDE argument is mandatory." (assert (shiftf magnitudep t) (magnitude) "The :MAGNITUDE argument was not provided.") (ccase keyword (:vs (assert (shiftf outcomep t) (outcome) "The :OUTCOME argument was not provided.")) (:beats 1) (:draws 1/2) (:loses-to 0)) (when (and (not (eql keyword :vs)) outcomep) (warn "The :OUTCOME argument has been ignored.")) (let ((elo-change (elo-change player opponent outcome magnitude))) (values (+ player elo-change) (- opponent elo-change))))