Not-understandable warning

*To*: mathgroup at smc.vnet.net*Subject*: [mg130385] Not-understandable warning*From*: JikaiRF at aol.com*Date*: Sat, 6 Apr 2013 21:53:06 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Dear members: I have a difficulty to understand programming in Mathematica. I input the following, based on a textbook titled ``Programming with Mathematica: An Introduction" by Paul Wellin, which is published by Cambridge University Press. mat = SparseArray[{i_, i_} \[RightArrow] 1, {4, 4}] Then, I received an answer as SparseArray[{i_, i_} \[RightArrow] 1, {4, 4}] with a warning as `` SparseArray::list: "List expected at position 1 in SparseArray[{i_, i_} \[RightArrow] 1, {4, 4}]". In this textbook, on page 32, there appears a correct answer as follows: SparseArray[<4>, {4,4}]. Why my Mathematica cannot understand my input? By the way, I use Mathematica 8.0.4.0 version and Mac OS 10.5.8. Sincerely, Fujio Takata.

**Follow-Ups**:**Re: Not-understandable warning***From:*Bob Hanlon <hanlonr357@gmail.com>