A decorate-sort-undecorate operation for Io

Specify a key for each item, and control how the keys are compared.

                Io> 1 to(10) asList sortKey(x, -(1)^(x) * x) sort
                ==> list(9, 7, 5, 3, 1, 2, 4, 6, 8, 10)

                Io> Directory with(".") files sortKey(lastInfoChangeDate) sort map(name)
                ==> ... listing of directory sorted by date
                

Two forms of sortKey are supported:

• files sortKey(lastInfoChangeDate)
• files sortKey(file, file lastInfoChangeDate)

Three forms of sort are supported:

• files sortKey(...) sort
• files sortKey(...) sort(<)
• files sortKey(...) sort(x, y, x < y)

foldl and foldr methods for list + iospec. Developed with Scott Baldwin.