use std, functional

data = ["apple", "banana", "cherry", "apricot", "coconut"]
println tomap(data, def(str) = str.substring(0, 1))
println tomap(data, def(str) = str.substring(0, 1), ::toUpperCase)
println tomap(data, def(str) = str.substring(0, 1), ::toUpperCase, ::joinValues)

def joinValues(oldValue, newValue) = oldValue + ", " + newValue