R package to know distances between city [or zipcode]

Dear All,

I have build a small package, that main object is to compute:

1. city names that are close to another city
2. city names that are close to a zipcode

I have two questions:

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a. for now, dataset is french data (zipcode + city + lat,lon): I would
like someting like:

library("mynewpackage")

setDefaultCountry("fr")
getCityNearToZipCode(1234)  => french city list

setDefaultCountry("uk")
getCityNearToZipCode(1234)  => uk city list

for now, there is only one dataset that I use directly in my R functions...

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b. Is this package needed, or is it redunctdant with an existing package ?

Antoine.