Options for Limit.
- To: mathgroup at smc.vnet.net
- Subject: [mg20832] Options for Limit.
- From: Jack Goldberg <jackgold at math.lsa.umich.edu>
- Date: Wed, 17 Nov 1999 03:40:47 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hi Group, The single option for Limit is Direction->1 or Direction->-1 I would suggest that these choices are counterintuitive and I offer an improvement. Here is why they are "less" than obviou. What is one's guess at the meaning of (*) Limit[ f[x], x->2, Direction -> 1 ] or, (**) Limit[ f[x], x->0, Direction -> -1 ] Are you sure? The book says that the limit in (*) is taken from smaller values (than 2, presumably), that is, "from below". Similarly, (**) is to be interpreted as the limit from above. These notations are not suggestive of the meanings and this is not good. Moreover it violates one of the professed goals in Mathematica - clarity of notation. (Give or take some of the cartoon notations representing infix functions, say @@@.) Here is an improvement(?) Limit[ f[x], x->2, Direction -> Below ] and Limit[ f[x], x->0, Direction -> Above ] If Mathematica adopts these suggestions, world peace will soon follow :-) Jack (The Wolverine) Goldberg Univ. of Mich