fast way to check an object is a member of a list?

Dear Francisco,

Is there any fast way to check that an object is a member of a list?

Here's a third interpretation of your question, to test whether somewhere 
is list there is an object identical to y:

any(sapply(list, function(x) identical(y, x)))

(You could, in addition, test whether there is an element named y in list, 
as Martin Maechler proposed.)

Does that do it?
  John

-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
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