# utility functions
# this function checks if a command exists and returns either true
# or false. This avoids using 'which' and 'whence', which will
# avoid problems with aliases for which on certain weird systems. :-)
# Usage: check_com [-c|-g] word
#   -c  only checks for external commands
#   -g  does the usual tests and also checks for global aliases
check_com() {
    emulate -L zsh
    local -i comonly gatoo

    if [[ $1 == '-c' ]] ; then
        (( comonly = 1 ))
        shift
    elif [[ $1 == '-g' ]] ; then
        (( gatoo = 1 ))
    else
        (( comonly = 0 ))
        (( gatoo = 0 ))
    fi

    if (( ${#argv} != 1 )) ; then
        printf 'usage: check_com [-c] <command>\n' >&2
        return 1
    fi

    if (( comonly > 0 )) ; then
        [[ -n ${commands[$1]}  ]] && return 0
        return 1
    fi

    if   [[ -n ${commands[$1]}    ]] \
      || [[ -n ${functions[$1]}   ]] \
      || [[ -n ${aliases[$1]}     ]] \
      || [[ -n ${reswords[(r)$1]} ]] ; then

        return 0
    fi

    if (( gatoo > 0 )) && [[ -n ${galiases[$1]} ]] ; then
        return 0
    fi

    return 1
}