[Richard Suchenwirth] - The following routine is not interesting for its
algorithm. Two days after the introduction of Euro cash, this little Euro calculator rather commits the variety of soon extinct European currencies to history:

 proc Euro {direction currency amount} {
    set usage "usage: Euro {from|to} currency amount"
    switch -- $currency {
        ATS - �S   {set f 13.7603}
        BEF - bfr  {set f 40.3399}
        DEM - DM   {set f 1.95583}
        ESP - Ptas {set f 166.386}
        FIM - Fmk  {set f 5.94573}
        FRF - FF   {set f 5.55957}
        GRD - Dr   {set f 340.750}
        IEP        {set f 0.7787564}
        ITL - Lit  {set f 1936.27}
        LUF - lfr  {set f 40.3399}
        NLG - hfl  {set f 2.20371}
        PTE - Esc  {set f 200.482}
        default    {error "bad currency $currency - $usage"}
    }
    switch -- $direction {
        from    {set f [expr {1./$f}]}
        to      {}
        default {error "bad direction $direction - $usage"}
    }
    format %.2f [expr {$amount*$f}]
 }
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[Arts and crafts of Tcl-Tk programming]