It's virtually impossible.
If you really mean local phone number formats, then usually it's of the form
n-nnnn or nn-nnnn or nnn-nnnn or nnnn-nnnn with hyphens as shown. I've seen
a directory in which the local phone number format was nnn and the directory
had more pages explaining the phone company than pages listing phone
numbers.
If you mean national phone number formats, then the traditional format was
nn(nnn)nnnn or nnn(nnn)nnnn or nnnn(nn)nnnn or nnnnn(n)nnnn, but one
currently popular format is nn-nnnn-nnnn or nnn-nnn-nnnn or nnnn-nn-nnnn or
nnnnn-n-nnnn, and another currently popular format is (nn)nnnn-nnnn or
(nnn)nnn-nnnn or (nnnn)nn-nnnn or (nnnnn)n-nnnn. For many years all three
formats were pretty much equal in popularity, but the traditional format is
less popular now. Other countries might be less flexible, but still I think
you're going to have trouble if you restrict the kinds of formats you
recognize.
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