2+2	= 4	ok
2+2*3	= 8	ok
-3^2+5	= 14	ok
* -pi^2	= -1	ok
/2	= 0.5	ok
sin pi/2	= 0	ok
3 sin( pi/2 )	= 3	ok
3 * 1/3	= 1	ok
1/3 * 3	= 1	ok
sqrt(5)^2	= 5	ok
-1234+1111	= -123	ok