I'm trying to define a function f which takes a list of reals. My purpose is to build a function which I can give a list of reals, integers or strings and have it build an appropriate probability distribution for.

So I'd like to do something like


I can easily match on Real/Integer/Strings. The part I can't figure out is how to match on a list of Real/Integer/String.

  • 1
    $\begingroup$ Almost there! f[{samples__Real}] or f[samples:{__Real}] $\endgroup$
    – mfvonh
    Commented Jun 24, 2014 at 4:02
  • $\begingroup$ That seems about right for what I want, thank you! I was close. However, samples is then treated as a "Squence[samples]", I was expecting just a list of reals/integers/strings like {1.0, 2.0, 3.0}. I'm obviously missing something in my understanding, any pointers to what that might be? I'm hoping to pass this list on to my makeRealDist function... $\endgroup$
    – Steven
    Commented Jun 24, 2014 at 4:13
  • $\begingroup$ The second option will give you a list. $\endgroup$
    – mfvonh
    Commented Jun 24, 2014 at 4:15
  • $\begingroup$ You can also use Repeated (..), but here BlankSequence (__) is simpler. $\endgroup$
    – mfvonh
    Commented Jun 24, 2014 at 4:20
  • 2
    $\begingroup$ Are you sure you want Real? This way 3 will be rejected, but 3. will be accepted. Why not check for NumericQ? but may be you really want Real. $\endgroup$
    – Nasser
    Commented Jun 24, 2014 at 4:26

1 Answer 1


I feel that the basics of this topic are well covered in my answer to:

Once you have read that and understand BlankSequence, Repeated, and Pattern you will understand that you could use either of these:

f1[samples : {__Real}]   := makeRealDist[samples]
f2[samples : {_Real ..}] := makeRealDist[samples]

If you wish to permit integers, fractions, etc, you can use NumberQ or perhaps even NumericQ.
Viable semantics include:

f3[samples_List] /; VectorQ[samples, NumberQ] := makeRealDist[samples]
f4[samples : {__?NumberQ}] := makeRealDist[samples]

Timings will show that the first forms (f1 and f3) are to be preferred:

SetAttributes[timeAvg, HoldFirst]
timeAvg[func_] := Do[If[# > 0.3, Return[#/5^i]] & @@ Timing@Do[func, {5^i}], {i, 0, 15}]

packed = Range[1, 1000, 0.0001];
timeAvg @ #[packed] & /@ {f1, f2, f3, f4}
{3.67616*10^-7, 0.1404, 5.59104*10^-7, 1.201}
  • $\begingroup$ Blacksequence? That sure soundeth sinister, nay, eldritch even. Goes well with your username, too :D $\endgroup$
    – Yves Klett
    Commented Jun 24, 2014 at 7:45
  • $\begingroup$ @Yves You mean you don't mutter dark incantations as you code? :o) $\endgroup$
    – Mr.Wizard
    Commented Jun 24, 2014 at 15:41
  • 1
    $\begingroup$ Well, more like PEGI 18 obscenities, at times. But they most assuredly do not help with the code as such. Hmm, worth a try. Now where did I put my Necronomicon again? Ah... right next to my NKS special edition and the Laundry files :D $\endgroup$
    – Yves Klett
    Commented Jun 24, 2014 at 16:03
  • $\begingroup$ f1[samples : {__Real}] := makeRealDist[samples] Reads cleanest to me, and has a benefit of being quite fast. Thank you all who helped. $\endgroup$
    – Steven
    Commented Jun 25, 2014 at 18:57
  • $\begingroup$ @user159805 You are welcome for my part. If you find this answer fully satisfactory please consider Accepting it. Also please consider choosing a more "human" username. $\endgroup$
    – Mr.Wizard
    Commented Jun 25, 2014 at 22:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.