#!/bin/false

intersection()
{
        comm -12 "$@"
}

difference()
{
        comm -23 "$@"
}

extract_words()
{
        grep -o -E '\b\w+\b' | sort -u
}

immediate_dependencies1()
{
        intersection \
                <(compgen -A function | sort -u) \
                <(declare -f "$1" | extract_words)
}

immediate_dependencies()
{
        (for f
        do
                immediate_dependencies1 "$f"
        done) | sort -u
}

recursive_dependencies()
{
        local seen=()
        while [ $# -gt 0 ]
        do
                seen+=("$@")
                set -- $(difference <(immediate_dependencies "$@") \
                                    <(printf '%s\n' "${seen[@]}" | sort -u))
        done
        printf '%s\n' "${seen[@]}"
}