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Mathematica Pattern matching and replace repeated

  1. Apr 22, 2012 #1
    I decided to ask here as well, because maybe someone will see it. Given a list of integers, use pattern matching and //.to create a rule that generates an ordered list of integers that are larger than the previous numbers in the list, eg given {3,5,2,0,6,1,8,4,9}, you should get {3,5,6,8,9}.I tried something like rules = {x_,y_,__}/;x>y -> {x,___}, calling our list L, L//.rules . I haven't really used this function before, what is the correct syntax? I want to check pairs of numbers and discard one if its less than the other. Any help would be appreciated.
     
  2. jcsd
  3. Apr 22, 2012 #2
    Here is one version (without rules):

    Code (Text):
    larger[lst_] := Select[Transpose[{lst, Prepend[Most[lst], lst[[1]] - 1]}], #[[1]] > #[[2]] &][[All, 1]]
    e.g.

    Code (Text):
    larger[{3, 5, 2, 0, 6, 1, 8, 4, 9}]
    gives:

    Code (Text):
    {3, 5, 6, 8, 9}
     
  4. Apr 22, 2012 #3
    Okay thanks
     
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