#!/bin/bash
pname=`basename $0`
stack=( )
top=1

function push_word () {
    stack[$top]="$1"
    top=$(( $top + 1 ))
#    echo $top / ${stack[@]} > /dev/tty
}

function pop_word () {
    top=$(( $top - 1 ))
    element="${stack[$top]}"
    stack[$top]=""
#    echo $top / ${stack[@]} > /dev/tty
}

echo Begin

while read word rest ; do
    case "$word" in
    [0-9]*)
        push_word "$word"
        ;;
    [-+*/])
        pop_word
        a=$element
        pop_word
        b=$element
        r=$(( $a $word $b ))
        push_word "$r"
        ;;
    dup)
        pop_word
        push_word $element
        push_word $element
        ;;
    print)
        if [ $top -eq 1 ] ; then
            echo "${pname} error: stack is empty."
            exit 1
        fi
        pop_word
        echo $element
        ;;
    *)
        echo "${pname} error: invalid token '$word'."
        exit 1
    esac
done
echo End
exit 0



#### interp                           -- 2003-02-21 18:42:35 -- pascal   ####