sets: additional supported operators
	e not in set s
	s1 union s2
	s1 inter s2
	s1 \ s2 -- set difference
	s1 subset s2
	card s -- size, cardinality

set comprehension: { x | x:T & P(x) }
	- the set of "x" from type "T" such that "P(x)"

sequences: additional supported operators
	[] -- empty sequence
	hd s -- head (first element)
	tl s -- tail (remaining sequence after removal of head)
	len s -- length
	s(i) -- selection of elements
	s1^s2 -- concatenation

maps: some operators
	dom m
	rng m
	m(x) -- return value for "x"

sequence enumeration: { e1, ..., eN }
	- example: [ 1, 2, 3, 4 ]

map enumeration: { k1 |-> v1, ..., kN |-> vN }
	- example: m = { 1 |-> 2, 3 |-> 4, 5 |-> 6 };

template for implicit specification of functions and operations
	f(p:T_p)r:T_r
		pre pre-f(p)
		post post-f(p, r)

template for explicit definition of functions
	f:T_p -> T_r
	f(p) == ...

template for explicit definition of operations (note the "==>" instead of "->")
	f:T_p ==> T_r
	f(p) == ...

symbol "()" is used to represent an empty list of operation arguments or no return value

creating instances of token types
	location : GPS = mk_token("50.105402,19.287645");

types with possible value "nil" (representing undefined)
	temperature : [int]

while loops
	(dcl max:int := 0;
	while <condition> do
		( stmt1;
		  ...
		  stmtN;
 		);
	return max
	);

pattern matching
	cases <branching expr>:
		<option expr 1> -> stmt,
		...
		<option expr N> -> stmt
	end;