Re: [Q] {a,b,c}->{{a,b},{b,c}}

*To*: mathgroup at smc.vnet.net*Subject*: [mg2600] Re: [Q] {a,b,c}->{{a,b},{b,c}}*From*: "Bart van der Zwet" <B.W.v.d.Zwet at stud.tue.nl>*Date*: Mon, 27 Nov 1995 21:34:21 -0500

Hello Mma-users, I while ago I posted a question here. I wanted to know how I could make {{a,b},{b,c}} out of {a,b,c} for instance, but then for any list. I received a number of different solutions that I shall mention in this mail. I've let them all solve the problem for the list : Range[10^4] and I include the timing to each solution. 1: Partition[list,2,1] 2.64 Second 2: Map[ Module[ {qux = absolutelyNothing}, (If[ qux === absolutelyNothing, qux = #; Sequence @@ {}, {qux, qux = #} ])& ], list ] 9.51 Second 3: Transpose[ { Drop[ list, -1 ], Drop[ list, 1 ] } ] 1.81 Second 4: r[ {x__} ] := Map[ Pattern[ #, Blank[] ]&, {x} ] -> Table[ { {x}[[i]], {x}[[i+1]] }, {i, 1, Length[ {x} ] - 1 } ] x /. r[x] 33.94 Second P.S. Not all responses are included, some didn't do exactly what I wanted or I couldn't get the answer with them. Some minor changes have been made in a solution. P.P.S. Thank you all for replying to my question, it's been of great help. Yours, Bart van der Zwet Student Mathematics Eindhoven University of Technology The Netherlands e-mail : B.W.v.d.Zwet at stud.tue.nl