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Re: Lost myHead, please help !!!

  • To: mathgroup at
  • Subject: [mg22371] Re: Lost myHead, please help !!!
  • From: "Allan Hayes" <hay at>
  • Date: Sat, 26 Feb 2000 22:04:58 -0500 (EST)
  • References: <897drf$>
  • Sender: owner-wri-mathgroup at


x = {{a}, {b, c}};

Apply[myHead, x]

myHead[{a}, {b, c}]

Abbreviation for Apply is

myHead @@ x

myHead[{a}, {b, c}]

And we can use ReplaceAll, but with a more discriminating pattern

x /. List[e___] -> myHead[e]

myHead[{a}, {b, c}]

Please note the search for parts to replace is top-down along branches, and
that having replaced {{a},{b,c}} with myHead[{a},{b,c}],no further work is
done on the new part, even though {a} and {b,c} both match List[e___].

"Antoine Zahnd" <antoine.zahnd at> wrote in message
news:897drf$5q0 at
> Hello everybody,
> I can't do the following (sigh)
> Let x = {{a},{b,c}}
> I would like to tranform it into something like myHead[{a},{b,c}]
> Of course x /. {List->myHead} doesn't work !
> Certainly it is simple, but so far I didn't get it.
> Thank you for your help.
> antoine.zahnd at

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