If the currency is not set using this function call, the currency defined in
the monetary representations in the current locale is used. If the monetary
formatting category "LC_MONETARY" of the C locale is not set,
"USD" is set as default.
set_currency(currency = NULL)character, the currency code compliant to ISO 4217 to use in
the requests (default = NULL, which defaults to the current system
locale settings).
None.
set_currency("CHF")