Suppose I have a list of named patterns:

listofPatterns = {a_Integer, b_Real, c_?StringQ}

I would like to have a mapping from a pattern to a certain value like:

foo[HoldPattern[a_Integer]] = 1;

foo[HoldPattern[b_Real]] = 1.5;

foo[HoldPattern[c_?StringQ]] = "foo"; 

In order to apply that on my list

foo /@ listofPatterns

And I expect to have {1, 1.5, "foo"} as a result. What is the best way to achieve that?

Thank you, Davit

  • $\begingroup$ Can you give a specific example? This is my input, this is my desired output. I do not understand what it means to apply a pattern to a list. $\endgroup$
    – Szabolcs
    Mar 12, 2020 at 17:12
  • $\begingroup$ Sure, This is my input foo /@ listofPatterns and this what I except {1, 1.5, "foo"} the question is to define foo correctly. $\endgroup$ Mar 12, 2020 at 17:15
  • $\begingroup$ Related, possible duplicates: (2778), (17892), (43923) $\endgroup$
    – Mr.Wizard
    Mar 12, 2020 at 21:45

1 Answer 1


When you need a pattern to match what is normally used as a pattern, you should use Verbatim:

foo[Verbatim[Pattern][_, Verbatim[Blank[Integer]]]] := 1

foo[Verbatim[Pattern][_, Verbatim[Blank[Real]]]] := 1.5

foo[Verbatim[PatternTest][_, StringQ]] := "foo"

foo /@ {a_Integer, b_Real, c_?StringQ}
(* {1, 1.5, "foo"} *)

When writing patterns like this, it's helpful to look at the full form of the patterns you want to match:

Column[FullForm /@ {a_Integer, b_Real, c_?StringQ}]

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.