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Pattern-rewriting Pattern triggers error?



I am trying to rewrite patterns. For example, I'd like to rewrite the pattern


jFoo_Integer

which has FullForm


Pattern[jFoo,Blank[Integer]]

into just


Blank[Integer]

In other words, I want to strip out the names of patterns. I tried the following



jFoo_Integer /. {Pattern[nym_, Blank[typ_]] :> {nym, typ}}

which does not match or reduce and produces the (IMO bogus) error message


Pattern::patvar: First element in pattern Pattern[nym_,Blank[typ_]] is not a valid pattern name. >>

I also tried


    Pattern[jFoo,Blank[Integer]] /. {Pattern[nym_, Blank[typ_]] :> {nym, typ}}
Pattern[jFoo,Blank[Integer]] /. {Verbatim[Pattern][nym_, Blank[typ_]] :> {nym, typ}}
jFoo_Integer /. {Verbatim[Pattern][nym_, Blank[typ_]] :> {nym, typ}}
jFoo_Integer /. {Verbatim[Pattern][nym_, Blank[typ_]] :> {nym, typ}}


all with exactly the same (failed) results.


Any hints, please & thanks?



Answer



What you want is probably


jFoo_Integer /. Verbatim[Pattern][nym_, Verbatim[Blank][typ_]] :> {nym, typ}
(* {jFoo, Integer} *)

The usage of Verbatim points it out




Verbatim[expr] represents expr in pattern matching, requiring that expr be matched exactly as it appears, with no substitutions for blanks or other transformations.



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