# Setting up an array and sorting the elements by key

# 5337 FMR BN1 9PU TQ 346088 50.8621241499 -0.0873836155 Falmer 771095 838150 920259 1009988 1045586 1033392

set fh [open railstats.xyz r]

proc byquantity {a b} {
        global uses
        # Following line is useful as a demo of how sort works
        # puts "$a .... $b"
        return [expr $uses($a) - $uses($b)]
        }

while {[set line [gets $fh]] != ""} {
        set fields [split $line "\t"]

        set placename [lindex $fields 6]
        set passengers [lindex $fields 8]

# NULL is not special in Tcl ... it just happens to be a value in
# our data file and we wish to elimitate data lines that have it in
# the passengers field

        if {$passengers != "NULL"} {
                set uses($placename) $passengers
        }
}

foreach pl [lsort -command byquantity [array names uses South*]] {
        puts [format "%8d %s" $uses($pl) $pl]

exit

# --------------- never gets past here in running
# sample results

munchkin:ta grahamellis$ tclsh ar_rail
    1942 South Bank
    6106 South Greenford
    7245 Southease
   35812 South Wigston
   42090 South Tottenham
   46146 South Hampstead
   50424 South Merton
   78239 South Milford
   80995 South Acton
  135017 Southminster
  185022 South Kenton
  200700 Southbourne
  245667 South Bermondsey
  252079 Southwick
  263038 Southbury
  265547 South Elmsall
  424306 South Gyle
  772355 South Croydon
  797470 Southend East
  859286 Southall
 1421305 Southampton Airport (Parkway)
 1582115 Southport
 1719370 Southend Victoria
 3018137 Southend Central
 4844998 Southampton Central
munchkin:ta grahamellis$
}