# Expression

An expression is composed of objects and operators. Objects in expression could be constant, variable, function, expression, etc.

```
$ 3>2;
1
$ x=true;
$ !x;
0
$ x=1 2 3
$ x*2;
[2,4,6]
$ y = 4 5 6;
$ x+y;
[5,7,9]
$ x+y*2;
$ (y-avg(y))*(y-avg(y));
[1,0,1]
$ t1 = table(x,y);
$ t1.y[0]\sum(t1.y);
0.266667
```