Type declaration for list arguments

Question

How can I make

f[n_Integer]=2*n

valid for a list of integers? For example:

f[nlist_Integer] := 2*nlist[[1]]

does not work because because nlist={1,3,2} is not an integer.

Edit: Same question with NumericQ (which does not work as Integer)?

Related: (6588) -- also see the many links therein. And performance notes here may be useful: (8650) — Mr.Wizard, Jun 16, 2015 at 7:11

elbOlita · Accepted Answer · 2015-06-16 06:14:31Z

5

F[listInt:{__Integer}]:=

The semicolon is just another way to name a pattern

answered Jun 16, 2015 at 6:06

elbOlita

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1

$\begingroup$ By chance, I just found nList_ /; VectorQ[nList, IntegerQ] reading a question. Your suggestion is shorter. $\endgroup$
– anderstood
Jun 16, 2015 at 6:08
$\begingroup$ How would you make it work with NumericQ̀? $\endgroup$
– anderstood
Jun 16, 2015 at 6:10
2

$\begingroup$ F[listInt:{__Integer}]? $\endgroup$
– Dr. belisarius
Jun 16, 2015 at 6:11
$\begingroup$ @belisarius Absolutely. It does not work with Integers. $\endgroup$
– anderstood
Jun 16, 2015 at 6:12
1

$\begingroup$ @anderstood F[b : {__?NumericQ}]? $\endgroup$
– Dr. belisarius
Jun 16, 2015 at 6:24

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