sc=

sgetc()
{
	sc="$(dd bs=1 count=1 2>/dev/null; printf '.')"
	sc="${sc%.}"
}

toktext()
{
	local t="${1}"
	shift 1
	local n=

	case "${t%${US}*}" in
		# Operators
		T_EOF)       n='';;
		T_NEWLINE)   n="${LF}";;
		T_AND)       n='&';;
		T_SEMI)      n=';';;
		T_AND_IF)    n='&&';;
		T_OR_IF)     n='||';;
		T_DSEMI)     n=';;';;
		T_LESS)      n='<';;
		T_GREAT)     n='>';;
		T_DLESS)     n='<<';;
		T_DGREAT)    n='>>';;
		T_LESS)      n='<';;
		T_LESSAND)   n='<&';;
		T_GREAT)     n='>';;
		T_GREATAND)  n='>&';;
		T_LESSGREAT) n='<>';;
		T_DLESSDASH) n='<<-';;
		T_CLOBBER)   n='>|';;
		T_PIPE)      n='|';;
		T_LPAREN)    n='(';;
		T_RPAREN)    n=')';;
		# Reserved words
		T_IF)     n='if';;
		T_THEN)   n='then';;
		T_ELSE)   n='else';;
		T_ELIF)   n='elif';;
		T_FI)     n='fi';;
		T_DO)     n='do';;
		T_DONE)   n='done';;
		T_CASE)   n='case';;
		T_ESAC)   n='esac';;
		T_WHILE)  n='while';;
		T_UNTIL)  n='until';;
		T_FOR)    n='for';;
		T_LBRACE) n='{';;
		T_RBRACE) n='}';;
		T_BANG)   n='!';;
		T_IN)     n='in';;
		# Special symbols
		T_NAME)            n="${t#*${US}}";;
		T_FNAME)           n="${t#*${US}}";;
		T_CMDNAME)         n="${t#*${US}}";;
		T_IO_NUMBER)       n="${t#*${US}}";;
		T_WORD)            n="${t#*${US}}";;
		T_ASSIGNMENT_WORD) n="${t#*${US}}";;
		# Unknown
		*) n='';;
	esac

	printf '%s' "${n}"
}

codegen_sub()
{
	local array="${1}"
	shift 1

	IFS="${RS}"
	for t in ${array}; do
		toktext "${t}"
		case "${t%${US}*}" in
			T_NEWLINE)
				;;
			*)
				printf ' '
				;;
		esac
	done
	unset IFS
}

# The token stack is encoded in a string in the following grammar:
#     Terminal symbols:
#         TOKEN
#     Production rules:
#         stack  = tokens [ '<SOH>' type '<STX>' stack '<ETX>' [ tokens ] ] ;
#         tokens = TOKEN { '<RS>' TOKEN } ;
#         type   = 'C' ;
# We need to recurse through this stack to get to all the tokens.
# Each element in the stack (an array of tokens) gets run through the codegen to
# become text that is inserted into the array below.
parse_stack()
{
	local array=

	array=''
	while :; do
		sgetc
		case "${sc}" in
			'')
				# EOF
				break
				;;
			"${SOH}")
				# New stack element
				sgetc
				case "${sc}" in
					'C')
						# Command substitution
						sgetc  # STX
						array="${array}$(parse_stack)."
						array="${array%.}"
						;;
				esac
				;;
			"${ETX}")
				# End of stack element
				break
				;;
			*)
				# Token character
				array="${array}${sc}"
				;;
		esac
	done
	codegen_sub "${array}"
}

codegen()
{
	local toks="${1}"
	shift 1

	if printf '%s' "${toks}" | parse_stack; then
		return 0
	else
		return 1
	fi
}