Mercurial > urweb
view lib/ur/option.ur @ 1101:b9abd6cded7b
Treat getCookie as effectful
author | Adam Chlipala <adamc@hcoop.net> |
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date | Tue, 29 Dec 2009 16:48:27 -0500 (2009-12-29) |
parents | 757dbac0454d |
children | a99b743a3087 |
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datatype t = datatype Basis.option fun eq [a] (_ : eq a) = mkEq (fn x y => case (x, y) of (None, None) => True | (Some x, Some y) => x = y | _ => False) fun ord [a] (_ : ord a) = mkOrd {Lt = fn x y => case (x, y) of (None, Some _) => True | (Some x, Some y) => x < y | _ => False, Le = fn x y => case (x, y) of (None, _) => True | (Some x, Some y) => x <= y | _ => False} fun isNone [a] x = case x of None => True | Some _ => False fun isSome [a] x = case x of None => False | Some _ => True fun mp [a] [b] f x = case x of None => None | Some y => Some (f y) fun bind [a] [b] f x = case x of None => None | Some y => f y fun get [a] (x : a) (o : option a) = case o of None => x | Some v => v