Pretty-print a list of lists as a table in Tcl

table.tcl

# Format a list of lists into an evently-spaced table for logging etc.
#
# @param llst    List of lists to format.
# @param padding Optionally specify how many spaces to separate fields, defaults to four.
# @return String of the pretty table.
proc table {llst {padding 4}} {
    set lengths [lmap each [join $llst] {string length $each}]
    set longest [expr $padding + max([join $lengths ","])]

    foreach lst $llst {
        foreach element $lst {
            set length    [string length $element]
            set remaining [expr $longest - $length]

            append result $element

            while {$remaining > 0} {
                append result " "

                incr remaining -1
            }
        }

        append result \n
    }

    return $result
}