lex
	ignore /[\t\n ]+/
	literal `^ `| `- `, `: `! `? `.
	literal `( `) `{ `} `* `& `+

	literal `-- `:> `:>> `<: `-> `**

	token word /[a-zA-Z_][a-zA-Z0-9_]*/
	token uint /[0-9]+/
end


def start 
	[expression]
	{
		print( xml( lhs ) )
	}

def expression 
	[expression `| term]
|	[expression `& term]
|	[expression `- term]
|	[expression `-- term]
|	[term]

def term 
	[factor_with_rep more_term]

# Can resolve the ambiguity by making more_term shortest match.
def more_term 
	[]
|	[factor_with_rep more_term]
|	[`. factor_with_rep more_term]
|	[`:> factor_with_rep more_term]
|	[`:>> factor_with_rep more_term]
|	[`<: factor_with_rep more_term]

def factor_with_rep 
	[factor_with_rep `*]
|	[factor_with_rep `**]
|	[factor_with_rep `?]
|	[factor_with_rep `+]
|	[factor_with_rep `{ factor_rep_num `}]
|	[factor_with_rep `{ `, factor_rep_num `}]
|	[factor_with_rep `{ factor_rep_num `, `}]
|	[factor_with_rep `{ factor_rep_num `, factor_rep_num `}]
|	[factor_with_neg]

def factor_rep_num 
	[uint]

def factor_with_neg 
	[`! factor_with_neg]
|	[`^ factor_with_neg]
|	[factor]

def factor 
	[alphabet_num]
|	[word]
|	[`( expression `)]

def alphabet_num 
	[uint]
|	[`- uint]

parse start[ stdin ]
print( '\n' )
##### IN #####
1 - 1
##### EXP #####
<start><expression><expression><term><factor_with_rep><factor_with_neg><factor><alphabet_num><uint>1</uint></alphabet_num></factor></factor_with_neg></factor_with_rep><more_term></more_term></term></expression><_literal_0007>-</_literal_0007><term><factor_with_rep><factor_with_neg><factor><alphabet_num><uint>1</uint></alphabet_num></factor></factor_with_neg></factor_with_rep><more_term></more_term></term></expression></start>