I need to store or use a matched pattern, as I need it later on. I'd like it so that the match is NOT confined in a pattern-like syntax like:

pattern /; test
lhs :> rhs /; test
lhs := rhs /; test


pattern ? test 

So I've been using this:

MatchQ[expr, x:pattern /; (var = x; True)]

Is there a neater way to do it, like:

var = MatchQ[expr, x:pattern extracode]
  • $\begingroup$ I suspect that you meant var==x. Could you provide a simple example of some inputs and the desired outputs? $\endgroup$ Nov 5, 2016 at 23:36
  • $\begingroup$ I then use var. If I want a return mechanism in a function (which has a Block or Module inside), I return var. $\endgroup$
    – kozner
    Nov 6, 2016 at 2:03
  • 2
    $\begingroup$ Would Cases perhaps do what you have in mind? $\endgroup$ Nov 6, 2016 at 19:29

1 Answer 1


It is difficult to discern from your question what you're actually trying to do. Daniel mentioned Cases, and maybe you could use that. If not you could use a utility function in a PatternTest like this:

set = (var = #; True) &;

MatchQ[{1, 2, 3}, (x : _List)?set]


{1, 2, 3}

This particular pattern could also be written concisely as x_List?set.

Also consider Sow and Reap:

sow = (Sow@#; True) &;

MatchQ[{1, 2, 3}, (x : _List)?sow] // Reap
{True, {{{1, 2, 3}}}}

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