I understand how to sort an array with a single value but how can I 
sort an  array w multiple values : [ integer_value1, float_value2]

an_array = [123, 42.50], [ 245, 25.45], [389, 32.69] ]

wich should give (sorting on the 2nd value)

sorted_array =>  [[ 245, 25.45], 389, 32.69], [123, 42.50]  ]

thanks for your help

joss