Re: List operations
- To: mathgroup at smc.vnet.net
- Subject: [mg25447] Re: List operations
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sun, 1 Oct 2000 02:44:29 -0400 (EDT)
- References: <8r196t$hs8@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Mat, Two ideas: Cases[data, {x_, y_} /; 3x + y^2 == 7] {{1, 2}, {2, 1}} op[{x_, y_}] := 3x + y^2 Select[data, op[#] == 7 &] {{1, 2}, {2, 1}} -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Matt Herman" <Henayni at hotmail.com> wrote in message news:8r196t$hs8 at smc.vnet.net... > > Hi, > > Suppose I have a list of ordered pairs {{a1,b1},{a2,b2},...,{an,bn}}. > What is an efficient way of pulling out all the pairs such that, if I do > an operation on the first element in the list, and another on the > second, and I sum them, they equal some predetermined constant? > > For instance, say 3*listpart[[1]]+listpart[[2]]^2 > > Thanks > >