{"id":31,"date":"2007-07-29T23:38:47","date_gmt":"2007-07-30T06:38:47","guid":{"rendered":"http:\/\/www.elbeno.com\/haskell_soe_blog\/?p=31"},"modified":"2008-01-07T22:09:49","modified_gmt":"2008-01-08T06:09:49","slug":"exercise-82","status":"publish","type":"post","link":"https:\/\/www.elbeno.com\/haskell_soe_blog\/?p=31","title":{"rendered":"Exercise 8.2"},"content":{"rendered":"<pre lang=\"haskell\">area (Rectangle a b) = abs(a * b)\r\narea (RtTriangle a b) = abs(a * b) \/ 2\r\narea (Ellipse r1 r2) = pi * abs(r1 * r2)\r\n\r\nperimeter (Rectangle s1 s2) = 2 * (abs s1 + abs s2)\r\nperimeter (RtTriangle s1 s2) = abs s1 + abs s2 + sqrt(s1^2 + s2^2)\r\nperimeter (Ellipse r1 r2)\r\n    | abs r1 > abs r2 = ellipsePerim (abs r1) (abs r2)\r\n    | otherwise = ellipsePerim (abs r2) (abs r1)\r\n    where ellipsePerim r1 r2 = let e = sqrt (r1^2 - r2^2) \/ r1\r\n                                   aux s i = nextEl e s i\r\n                                   s = scanl aux (0.25 * e^2) [2..]\r\n                                   test x = x > epsilon\r\n                                   sSum = sum (takeWhile test s)\r\n                               in 2 * r1 * pi * (1 - sSum)<\/pre>\n<p>The definitions dealing with other kinds of <tt>Shape<\/tt> need not be changed.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>area (Rectangle a b) = abs(a * b) area (RtTriangle a b) = abs(a * b) \/ 2 area (Ellipse r1 r2) = pi * abs(r1 * r2) perimeter (Rectangle s1 s2) = 2 * (abs s1 + abs s2) perimeter (RtTriangle s1 s2) = abs s1 + abs s2 + sqrt(s1^2 + s2^2) perimeter [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=\/wp\/v2\/posts\/31"}],"collection":[{"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=31"}],"version-history":[{"count":0,"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=\/wp\/v2\/posts\/31\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=31"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=31"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.elbeno.com\/haskell_soe_blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=31"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}