#!/bin/sh

# INTERCAL unary and binary operators written in dd/sh (base 2 only)
# with an example simple calculator

# usage: type simple numbers with an optional operation, for example:
# #1
# #V1
# #&1
# #1~#2

# /bin/rm is not really required, but it is nice to clean up temporary files

PATH=
dd=/bin/dd
rm=/bin/rm

# temporary files we might need
tmp=/tmp/silly.$$
trap "$rm -f $tmp $tmp.*; exit" 0 HUP INT QUIT

# from now on, no more rm - the above trap is enough
unset rm

# we do interesting things with IFS, but better save it...
saveIFS="$IFS"

# in case "echo" is not a shell builtin...

Echo () {
case "$1" in
  -n) shift
      $dd of=$tmp 2>/dev/null <<EOF 
$@
EOF
      IFS="+"
      set `$dd if=$tmp bs=1 of=/dev/null skip=1 2>&1`
      IFS="$saveIFS"
      $dd if=$tmp bs=1 count=$1 2>/dev/null
      ;;
  *)  $dd 2>/dev/null <<EOF 
$@
EOF
      ;;
esac
}

# useful functions

true () {
    return 0;
}

false () {
    return 1;
}

zero () {
  ( trap 'go=false' PIPE
    go=true
    while $go
    do
      $dd "if=$0"
      case "$?" in
	0) ;;
	*) go=false ;;
      esac
    done
  ) 2>/dev/null
}

# we use this during recursion

stash () {
    eval sname=\$stash_$1
    case "$sname" in
	?*) sname="s$sname" ;;
	*)  sname="s_$1" ;;
    esac
    eval stash_$1="$sname"
    eval $sname=\$$1
}

retrieve () {
    eval fname=\$stash_$1
    eval value=\$$fname
    eval $1=\$$fname
    eval sv=\$stash_$1
    value="`Echo -n $sv | $dd bs=1 skip=1 2>/dev/null`"
    eval stash_$1=$value
}

# parse simple INTERCAL expressions

parse () {
    if ! parse_term
    then
	return 1
    fi
    while true
    do
	case "$text" in
	    '¢'*) f=f_interleave ;;
	    '$'*) f=f_interleave ;;
	    '£'*) f=f_interleave ;;
	    '~'*) f=f_select ;;
	    *)    return 0 ;;
	esac
	text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
	left="$result"
	stash left
	stash f
	if ! parse_term
	then
	    retrieve f
	    retrieve left
	    return 1
	fi
	retrieve f
	retrieve left
	right="$result"
	if ! $f result "$left" "$right"
	then
	    return 1
	fi
    done
}

parse_term () {
    code="`Echo -n "$text" | $dd bs=1 count=1 2>/dev/null`"
    text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
    case "$code" in
	'#') if parse_number
	     then
		 return 0
	     else
		 return 1
	     fi
	     ;;
	'"') if ! parse
	     then
		 return 1
	     fi
	     case "$text" in
		  '"'*) ;;
		  *)    return 1 ;;
	     esac
	     text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
	     return 0
	     ;;
	"'") if ! parse
	     then
		 return 1
	     fi
	     case "$text" in
		  "'"*) ;;
		  *)    return 1 ;;
	     esac
	     text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
	     return 0
	     ;;
	*)   return 1
	     ;;
    esac
}

parse_number () {
    case "$text" in
	'V'*) f=f_or;  c=true ;;
	'¥'*) f=f_xor; c=true ;;
	'?'*) f=f_xor; c=true ;;
	'&'*) f=f_and; c=true ;;
	*)    f=true;  c=false ;;
    esac
    stash f
    problem=true
    if $c
    then
	text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
	if parse_number
	then
	    problem=false
	fi
    else
	result=0000000000000000
	while parse_n1
	do
	    problem=false
	done
    fi
    retrieve f
    if $problem
    then
	return 1
    fi
    arg="$result"
    $f result "$arg"
    return 0
}

parse_n1 () {
    digit="`Echo -n "$text" | $dd bs=1 count=1 2>/dev/null`"
    case "$digit" in
	0) num=0000000000000000 ;;
	1) num=1000000000000000 ;;
	2) num=0100000000000000 ;;
	3) num=1100000000000000 ;;
	4) num=0010000000000000 ;;
	5) num=1010000000000000 ;;
	6) num=0110000000000000 ;;
	7) num=1110000000000000 ;;
	8) num=0001000000000000 ;;
	9) num=1001000000000000 ;;
	*) return 1 ;;
    esac
    text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
    # check if result is already too big
    case "$result" in
	*1) return 1 ;;
	*01) return 1 ;;
	*001) return 1 ;;
    esac
    # shift left result by 1 and 3
    res1="0`Echo -n "$result" | $dd bs=1 count=15 2>/dev/null`"
    res3="000`Echo -n "$result" | $dd bs=1 count=13 2>/dev/null`"
    # now add the numbers
    c1=0
    c2=0
    temp=''
    for digit in 0 1 2 3 4 5 6 7 8 9 A B C D E F
    do
	dig1="`Echo -n "$res1" | $dd bs=1 count=1 2>/dev/null`"
	res1="`Echo -n "$res1" | $dd bs=1 skip=1 2>/dev/null`"
	dig3="`Echo -n "$res3" | $dd bs=1 count=1 2>/dev/null`"
	res3="`Echo -n "$res3" | $dd bs=1 skip=1 2>/dev/null`"
	dign="`Echo -n "$num" | $dd bs=1 count=1 2>/dev/null`"
	num="`Echo -n "$num" | $dd bs=1 skip=1 2>/dev/null`"
	case "$dig1$dign$dig3$c1" in
	    0000) add=0; carry=0 ;;
	    0001) add=1; carry=0 ;;
	    0010) add=1; carry=0 ;;
	    0011) add=0; carry=1 ;;
	    0100) add=1; carry=0 ;;
	    0101) add=0; carry=1 ;;
	    0110) add=0; carry=1 ;;
	    0111) add=1; carry=1 ;;
	    1000) add=1; carry=0 ;;
	    1001) add=0; carry=1 ;;
	    1010) add=0; carry=1 ;;
	    1011) add=1; carry=1 ;;
	    1100) add=0; carry=1 ;;
	    1101) add=1; carry=1 ;;
	    1110) add=1; carry=1 ;;
	    1111) add=1; carry=2 ;;
	esac
	temp="$temp$add"
	case "$c2$carry" in
	    00) c1=0; c2=0 ;;
	    01) c1=1; c2=0 ;;
	    02) c1=0; c2=1 ;;
	    10) c1=1; c2=0 ;;
	    11) c1=0; c2=1 ;;
	    12) c1=1; c2=1 ;;
	esac
    done
    case "$c1" in
	1) return 1 ;;
    esac
    case "$c2" in
	1) return 1 ;;
    esac
    result="$temp"
    return 0
}

reverse () {
    text="$1"
    result=''
    while true
    do
	case "$text" in
	    ?*) ;;
	    *)  return ;;
	esac
	first="`Echo -n "$text" | $dd bs=1 count=1 2>/dev/null`"
	text="`Echo -n "$text" | $dd bs=1 skip=1 2>/dev/null`"
	result="$first$result"
    done
}

num2wimp () {
    reverse "$1"
    num="$result"
    result=0
    while true
    do
	case "$num" in
	    ?*) ;;
	    *)  break ;;
	esac
	carry="`Echo -n "$num" | $dd bs=1 count=1 2>/dev/null`"
	num="`Echo -n "$num" | $dd bs=1 skip=1 2>/dev/null`"
	temp="$result"
	result=''
	while true
	do
	    case "$temp" in
		?*) ;;
		*)  break ;;
	    esac
	    dig="`Echo -n "$temp" | $dd bs=1 count=1 2>/dev/null`"
	    temp="`Echo -n "$temp" | $dd bs=1 skip=1 2>/dev/null`"
	    > $tmp
	    zero | $dd bs=2 count=$dig 2>/dev/null >> $tmp
	    zero | $dd bs=1 count=$carry 2>/dev/null >> $tmp
	    IFS="+"
	    set `$dd if=$tmp bs=1 of=/dev/null 2>&1`
	    IFS="$saveIFS"
	    case "$1" in
		??*) carry="`Echo -n "$1" | $dd bs=1 count=1 2>/dev/null`"
		     ndig="`Echo -n "$1" | $dd bs=1 skip=1 2>/dev/null`"
		     ;;
		?)   carry=0
		     ndig="$1"
		     ;;
		*)   carry=0
		     ndig=0
		     ;;
	    esac
	    result="$result$ndig"
	done
	case "$carry" in
	    0) ;;
	    *) result="$result$carry" ;;
	esac
    done
    reverse "$result"
}

# INTERCAL operators

f_interleave () {
    res="$1"
    num1="$2"
    num2="$3"
    case "$num1" in
	????????????????)
	    ;;
	????????????????0000000000000000)
	    num1="`Echo "$num1" | $dd bs=1 count=16 2>/dev/null`"
	    ;;
	*)
	    Echo "Too many spots" 2>&1
	    return 1
	    ;;
    esac
    case "$num2" in
	????????????????)
	    ;;
	????????????????0000000000000000)
	    num2="`Echo "$num2" | $dd bs=1 count=16 2>/dev/null`"
	    ;;
	*)
	    Echo "Too many spots" 2>&1
	    return 1
	    ;;
    esac
    val=''
    for bits in 0 1 2 3 4 5 6 7 8 9 A B C D E F
    do
	dig1="`Echo -n "$num1" | $dd bs=1 count=1 2>/dev/null`"
	num1="`Echo -n "$num1" | $dd bs=1 skip=1 2>/dev/null`"
	dig2="`Echo -n "$num2" | $dd bs=1 count=1 2>/dev/null`"
	num2="`Echo -n "$num2" | $dd bs=1 skip=1 2>/dev/null`"
	val="$val$dig2$dig1"
    done
    eval $res=$val
    return 0
}

f_select () {
    res="$1"
    num1="$2"
    num2="$3"
    case "$num2" in
	????????????????)
	    case "$num1" in
		????????????????)
		    ;;
		????????????????????????????????)
		    num1="`Echo "$num1" | $dd bs=1 count=16 skip=16 2>/dev/null`"
		    ;;
	    esac
	    ;;
	????????????????????????????????)
	    case "$num1" in
		????????????????)
		    num1="${num1}0000000000000000"
		    ;;
		????????????????????????????????)
		    ;;
	    esac
	    ;;
    esac
    val=''
    end=''
    while true
    do
	case "$num1" in
	    ?*) ;;
	    *) break ;;
	esac
	dig1="`Echo -n "$num1" | $dd bs=1 count=1 2>/dev/null`"
	num1="`Echo -n "$num1" | $dd bs=1 skip=1 2>/dev/null`"
	dig2="`Echo -n "$num2" | $dd bs=1 count=1 2>/dev/null`"
	num2="`Echo -n "$num2" | $dd bs=1 skip=1 2>/dev/null`"
	case "$dig2" in
	    0) end="${end}0" ;;
	    1) val="${val}$dig1" ;;
	esac
    done
    eval $res=$val$end
    return 0
}

f_or () {
    unary "$1" "$2" 0 1 1 1
}

f_xor () {
    unary "$1" "$2" 0 1 1 0
}

f_and () {
    unary "$1" "$2" 0 0 0 1
}

unary () {
    res="$1"
    num="$2"
    d1="$3"
    d2="$4"
    d3="$5"
    d4="$6"
    case "$num" in
	0*) num="${num}0" ;;
	1*) num="${num}1" ;;
	*)  Echo "Something bad happened, bit value is wrong" >&2 ; return 1 ;;
    esac
    val=''
    while true
    do
	case "$num" in
	    ?) break ;;
	esac
	dig="`Echo -n "$num" | $dd bs=1 count=2 2>/dev/null`"
	num="`Echo -n "$num" | $dd bs=1 skip=1 2>/dev/null`"
	case "$dig" in
	    00) val="${val}$d1" ;;
	    01) val="${val}$d2" ;;
	    10) val="${val}$d3" ;;
	    11) val="${val}$d4" ;;
	esac
    done
    eval $res="$val"
}

# the main program

Echo -n "? "
while read line
do
    case "$line" in
	?*) ;;
	*)  Echo -n "?? "
	    continue
	    ;;
    esac
    text="$line"
    parse
    case "$result" in
	*?) case "$text" in
		?*) Echo "Parse error just before $text"
		    ;;
		*)  num2wimp "$result"
		    Echo "$line -> $result"
		    ;;
	    esac
	    ;;
	*)  Echo "Something went wrong" ;;
    esac
    Echo -n "? "
done