Pattern syntax

The basic form of a pattern is a literal, which that matches only a single integer, real number, string, etc. Complex patterns can be constructed inductively using datatype constructors, tuples, lists, and logical pattern connectives.

The syntax of the patterns is as follows:

Pat	::=	Integer	matches integer literal
	|	Real	matches real literal
	|	Char	matches character literal
	|	Quark	matches quark literal
	|	String	matches string literal
	|	Regexp	matches any string that matches regexp
	|	Pat_Var	a pattern variable; matches anything
	|	_	wild card; matches anything
	|	Cons	matches a datatype constructor
	|	Cons PatArg	a constructor application pattern
	|	Id as Pat	binds a variable to the sub-pattern
	|	Pat : Type_Exp	typed pattern
	|	Pat  - - Pat	matches either pattern
	|	Pat && Pat	matches both patterns
	|	! Pat	matches anything but the pattern
	|	( Pat )	Grouping
	|	#[ Pat, ¼ , Pat ]	list pattern; exact length match
	|	#[ Pat, ¼ , Pat ... ]	list pattern; non-exact length match
	|	[ - Pat, ¼ , Pat - ]	vector pattern; exact length match
	|	[ - Pat, ¼ , Pat ... - ]	vector pattern; matches to the left
	|	[ - ... Pat, ¼ , Pat - ]	vector pattern; matches to the right
PatArg	::=	Pat
	|	( Pat, ¼ , Pat )
	|	{ Lab_Pat, ¼ , Lab_Pat [ ... ] }
Lab_Pat	::=	Id = Pat
Pat_Var	::=	Id
	|	?Id